From 93eaa3f0808fdfc13a0105e50ff3e08bff77c69f Mon Sep 17 00:00:00 2001 From: Tk-Glitch Date: Wed, 3 Mar 2021 17:27:05 +0100 Subject: [PATCH] linux512-rc-tkg: Import futex2 interface patchset and add missing config entry for USER_NS_UNPRIVILEGED (Arch patch) --- PKGBUILD | 5 +- linux-tkg-config/5.12/config.x86_64 | 1 + .../5.12/0007-v5.12-futex2_interface.patch | 4530 +++++++++++++++++ 3 files changed, 4534 insertions(+), 2 deletions(-) create mode 100644 linux-tkg-patches/5.12/0007-v5.12-futex2_interface.patch diff --git a/PKGBUILD b/PKGBUILD index 7126b09..48b7dbc 100644 --- a/PKGBUILD +++ b/PKGBUILD @@ -426,7 +426,7 @@ case $_basever in #0005-glitched-pds.patch 0006-add-acs-overrides_iommu.patch 0007-v5.12-fsync.patch - #0007-v5.12-futex2_interface.patch + 0007-v5.12-futex2_interface.patch #0008-5.12-bcachefs.patch #0009-glitched-ondemand-bmq.patch #0009-glitched-bmq.patch @@ -436,7 +436,7 @@ case $_basever in ) sha256sums=('d57d9b8c595960bc21137c2d6312aca417029cc45a264f500d047ee1270193d5' 'SKIP' - '5cc3767b4005fc21c53863ceda75f287a9d2be772dbdee861a5cbec9cc62c1bd' + 'cb0345a190154935333d88b9fa66df9c29de11d0f6df416950edbae23ec3f1aa' '1e15fc2ef3fa770217ecc63a220e5df2ddbcf3295eb4a021171e7edd4c6cc898' '66a03c246037451a77b4d448565b1d7e9368270c7d02872fbd0b5d024ed0a997' 'f6383abef027fd9a430fd33415355e0df492cdc3c90e9938bf2d98f4f63b32e6' @@ -445,6 +445,7 @@ case $_basever in '7058e57fd68367b029adc77f2a82928f1433daaf02c8c279cb2d13556c8804d7' '19661ec0d39f9663452b34433214c755179894528bf73a42f6ba52ccf572832a' 'b302ba6c5bbe8ed19b20207505d513208fae1e678cf4d8e7ac0b154e5fe3f456' + 'e67872500624b9369641a953cd1ba87b720d6f5dc95b74adb9a7cf51cb4ad4bd' '7fb1104c167edb79ec8fbdcde97940ed0f806aa978bdd14d0c665a1d76d25c24') ;; esac diff --git a/linux-tkg-config/5.12/config.x86_64 b/linux-tkg-config/5.12/config.x86_64 index 53e5310..d21be17 100644 --- a/linux-tkg-config/5.12/config.x86_64 +++ b/linux-tkg-config/5.12/config.x86_64 @@ -200,6 +200,7 @@ CONFIG_UTS_NS=y CONFIG_TIME_NS=y CONFIG_IPC_NS=y CONFIG_USER_NS=y +CONFIG_USER_NS_UNPRIVILEGED=y CONFIG_PID_NS=y CONFIG_NET_NS=y CONFIG_CHECKPOINT_RESTORE=y diff --git a/linux-tkg-patches/5.12/0007-v5.12-futex2_interface.patch b/linux-tkg-patches/5.12/0007-v5.12-futex2_interface.patch new file mode 100644 index 0000000..1d7d89e --- /dev/null +++ b/linux-tkg-patches/5.12/0007-v5.12-futex2_interface.patch @@ -0,0 +1,4530 @@ +From e434311562a21e6fc917edeadac7b25732c6ea60 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:00 -0300 +Subject: [PATCH] futex2: Implement wait and wake functions +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Create a new set of futex syscalls known as futex2. This new interface +is aimed to implement a more maintainable code, while removing obsolete +features and expanding it with new functionalities. + +Implements wait and wake semantics for futexes, along with the base +infrastructure for future operations. The whole wait path is designed to +be used by N waiters, thus making easier to implement vectorized wait. + +* Syscalls implemented by this patch: + +- futex_wait(void *uaddr, unsigned int val, unsigned int flags, + struct timespec *timo) + + The user thread is put to sleep, waiting for a futex_wake() at uaddr, + if the value at *uaddr is the same as val (otherwise, the syscall + returns immediately with -EAGAIN). timo is an optional timeout value + for the operation. + + Return 0 on success, error code otherwise. + + - futex_wake(void *uaddr, unsigned long nr_wake, unsigned int flags) + + Wake `nr_wake` threads waiting at uaddr. + + Return the number of woken threads on success, error code otherwise. + +** The `flag` argument + + The flag is used to specify the size of the futex word + (FUTEX_[8, 16, 32]). It's mandatory to define one, since there's no + default size. + + By default, the timeout uses a monotonic clock, but can be used as a realtime + one by using the FUTEX_REALTIME_CLOCK flag. + + By default, futexes are of the private type, that means that this user address + will be accessed by threads that shares the same memory region. This allows for + some internal optimizations, so they are faster. However, if the address needs + to be shared with different processes (like using `mmap()` or `shm()`), they + need to be defined as shared and the flag FUTEX_SHARED_FLAG is used to set that. + + By default, the operation has no NUMA-awareness, meaning that the user can't + choose the memory node where the kernel side futex data will be stored. The + user can choose the node where it wants to operate by setting the + FUTEX_NUMA_FLAG and using the following structure (where X can be 8, 16, or + 32): + + struct futexX_numa { + __uX value; + __sX hint; + }; + + This structure should be passed at the `void *uaddr` of futex functions. The + address of the structure will be used to be waited/waken on, and the + `value` will be compared to `val` as usual. The `hint` member is used to + defined which node the futex will use. When waiting, the futex will be + registered on a kernel-side table stored on that node; when waking, the futex + will be searched for on that given table. That means that there's no redundancy + between tables, and the wrong `hint` value will led to undesired behavior. + Userspace is responsible for dealing with node migrations issues that may + occur. `hint` can range from [0, MAX_NUMA_NODES], for specifying a node, or + -1, to use the same node the current process is using. + + When not using FUTEX_NUMA_FLAG on a NUMA system, the futex will be stored on a + global table on some node, defined at compilation time. + +** The `timo` argument + +As per the Y2038 work done in the kernel, new interfaces shouldn't add timeout +options known to be buggy. Given that, `timo` should be a 64bit timeout at +all platforms, using an absolute timeout value. + +Signed-off-by: André Almeida +--- + +[RFC Add futex2 syscall 0/0] + +Hi, + +This patch series introduces the futex2 syscalls. + +* What happened to the current futex()? + +For some years now, developers have been trying to add new features to +futex, but maintainers have been reluctant to accept then, given the +multiplexed interface full of legacy features and tricky to do big +changes. Some problems that people tried to address with patchsets are: +NUMA-awareness[0], smaller sized futexes[1], wait on multiple futexes[2]. +NUMA, for instance, just doesn't fit the current API in a reasonable +way. Considering that, it's not possible to merge new features into the +current futex. + + ** The NUMA problem + + At the current implementation, all futex kernel side infrastructure is + stored on a single node. Given that, all futex() calls issued by + processors that aren't located on that node will have a memory access + penalty when doing it. + + ** The 32bit sized futex problem + + Embedded systems or anything with memory constrains would benefit of + using smaller sizes for the futex userspace integer. Also, a mutex + implementation can be done using just three values, so 8 bits is enough + for various scenarios. + + ** The wait on multiple problem + + The use case lies in the Wine implementation of the Windows NT interface + WaitMultipleObjects. This Windows API function allows a thread to sleep + waiting on the first of a set of event sources (mutexes, timers, signal, + console input, etc) to signal. Considering this is a primitive + synchronization operation for Windows applications, being able to quickly + signal events on the producer side, and quickly go to sleep on the + consumer side is essential for good performance of those running over Wine. + +[0] https://lore.kernel.org/lkml/20160505204230.932454245@linutronix.de/ +[1] https://lore.kernel.org/lkml/20191221155659.3159-2-malteskarupke@web.de/ +[2] https://lore.kernel.org/lkml/20200213214525.183689-1-andrealmeid@collabora.com/ + +* The solution + +As proposed by Peter Zijlstra and Florian Weimer[3], a new interface +is required to solve this, which must be designed with those features in +mind. futex2() is that interface. As opposed to the current multiplexed +interface, the new one should have one syscall per operation. This will +allow the maintainability of the API if it gets extended, and will help +users with type checking of arguments. + +In particular, the new interface is extended to support the ability to +wait on any of a list of futexes at a time, which could be seen as a +vectored extension of the FUTEX_WAIT semantics. + +[3] https://lore.kernel.org/lkml/20200303120050.GC2596@hirez.programming.kicks-ass.net/ + +* The interface + +The new interface can be seen in details in the following patches, but +this is a high level summary of what the interface can do: + + - Supports wake/wait semantics, as in futex() + - Supports requeue operations, similarly as FUTEX_CMP_REQUEUE, but with + individual flags for each address + - Supports waiting for a vector of futexes, using a new syscall named + futex_waitv() + - Supports variable sized futexes (8bits, 16bits and 32bits) + - Supports NUMA-awareness operations, where the user can specify on + which memory node would like to operate + +* Implementation + +The internal implementation follows a similar design to the original futex. +Given that we want to replicate the same external behavior of current +futex, this should be somewhat expected. For some functions, like the +init and the code to get a shared key, I literally copied code and +comments from kernel/futex.c. I decided to do so instead of exposing the +original function as a public function since in that way we can freely +modify our implementation if required, without any impact on old futex. +Also, the comments precisely describes the details and corner cases of +the implementation. + +Each patch contains a brief description of implementation, but patch 6 +"docs: locking: futex2: Add documentation" adds a more complete document +about it. + +* The patchset + +This patchset can be also found at my git tree: + +https://gitlab.collabora.com/tonyk/linux/-/tree/futex2-dev + + - Patch 1: Implements wait/wake, and the basics foundations of futex2 + + - Patches 2-4: Implement the remaining features (shared, waitv, requeue). + + - Patch 5: Adds the x86_x32 ABI handling. I kept it in a separated + patch since I'm not sure if x86_x32 is still a thing, or if it should + return -ENOSYS. + + - Patch 6: Add a documentation file which details the interface and + the internal implementation. + + - Patches 7-13: Selftests for all operations along with perf + support for futex2. + + - Patch 14: While working on porting glibc for futex2, I found out + that there's a futex_wake() call at the user thread exit path, if + that thread was created with clone(..., CLONE_CHILD_SETTID, ...). In + order to make pthreads work with futex2, it was required to add + this patch. Note that this is more a proof-of-concept of what we + will need to do in future, rather than part of the interface and + shouldn't be merged as it is. + +* Testing: + +This patchset provides selftests for each operation and their flags. +Along with that, the following work was done: + + ** Stability + + To stress the interface in "real world scenarios": + + - glibc[4]: nptl's low level locking was modified to use futex2 API + (except for robust and PI things). All relevant nptl/ tests passed. + + - Wine[5]: Proton/Wine was modified in order to use futex2() for the + emulation of Windows NT sync mechanisms based on futex, called "fsync". + Triple-A games with huge CPU's loads and tons of parallel jobs worked + as expected when compared with the previous FUTEX_WAIT_MULTIPLE + implementation at futex(). Some games issue 42k futex2() calls + per second. + + - Full GNU/Linux distro: I installed the modified glibc in my host + machine, so all pthread's programs would use futex2(). After tweaking + systemd[6] to allow futex2() calls at seccomp, everything worked as + expected (web browsers do some syscall sandboxing and need some + configuration as well). + + - perf: The perf benchmarks tests can also be used to stress the + interface, and they can be found in this patchset. + + ** Performance + + - For comparing futex() and futex2() performance, I used the artificial + benchmarks implemented at perf (wake, wake-parallel, hash and + requeue). The setup was 200 runs for each test and using 8, 80, 800, + 8000 for the number of threads, Note that for this test, I'm not using + patch 14 ("kernel: Enable waitpid() for futex2") , for reasons explained + at "The patchset" section. + + - For the first three ones, I measured an average of 4% gain in + performance. This is not a big step, but it shows that the new + interface is at least comparable in performance with the current one. + + - For requeue, I measured an average of 21% decrease in performance + compared to the original futex implementation. This is expected given + the new design with individual flags. The performance trade-offs are + explained at patch 4 ("futex2: Implement requeue operation"). + +[4] https://gitlab.collabora.com/tonyk/glibc/-/tree/futex2 +[5] https://gitlab.collabora.com/tonyk/wine/-/tree/proton_5.13 +[6] https://gitlab.collabora.com/tonyk/systemd + +* FAQ + + ** "Where's the code for NUMA and FUTEX_8/16?" + + The current code is already complex enough to take some time for + review, so I believe it's better to split that work out to a future + iteration of this patchset. Besides that, this RFC is the core part of the + infrastructure, and the following features will not pose big design + changes to it, the work will be more about wiring up the flags and + modifying some functions. + + ** "And what's about FUTEX_64?" + + By supporting 64 bit futexes, the kernel structure for futex would + need to have a 64 bit field for the value, and that could defeat one of + the purposes of having different sized futexes in the first place: + supporting smaller ones to decrease memory usage. This might be + something that could be disabled for 32bit archs (and even for + CONFIG_BASE_SMALL). + + Which use case would benefit for FUTEX_64? Does it worth the trade-offs? + + ** "Where's the PI/robust stuff?" + + As said by Peter Zijlstra at [3], all those new features are related to + the "simple" futex interface, that doesn't use PI or robust. Do we want + to have this complexity at futex2() and if so, should it be part of + this patchset or can it be future work? + +Thanks, + André +--- + MAINTAINERS | 2 +- + arch/arm/tools/syscall.tbl | 2 + + arch/arm64/include/asm/unistd.h | 2 +- + arch/arm64/include/asm/unistd32.h | 4 + + arch/x86/entry/syscalls/syscall_32.tbl | 2 + + arch/x86/entry/syscalls/syscall_64.tbl | 2 + + include/linux/syscalls.h | 7 + + include/uapi/asm-generic/unistd.h | 8 +- + include/uapi/linux/futex.h | 5 + + init/Kconfig | 7 + + kernel/Makefile | 1 + + kernel/futex2.c | 619 ++++++++++++++++++ + kernel/sys_ni.c | 4 + + tools/include/uapi/asm-generic/unistd.h | 8 +- + .../arch/x86/entry/syscalls/syscall_64.tbl | 2 + + 15 files changed, 671 insertions(+), 4 deletions(-) + create mode 100644 kernel/futex2.c + +diff --git a/MAINTAINERS b/MAINTAINERS +index d92f85ca831d..01aceb92aa40 100644 +--- a/MAINTAINERS ++++ b/MAINTAINERS +@@ -7370,7 +7370,7 @@ F: Documentation/locking/*futex* + F: include/asm-generic/futex.h + F: include/linux/futex.h + F: include/uapi/linux/futex.h +-F: kernel/futex.c ++F: kernel/futex* + F: tools/perf/bench/futex* + F: tools/testing/selftests/futex/ + +diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl +index dcc1191291a2..2bf93c69e00a 100644 +--- a/arch/arm/tools/syscall.tbl ++++ b/arch/arm/tools/syscall.tbl +@@ -456,3 +456,5 @@ + 440 common process_madvise sys_process_madvise + 441 common epoll_pwait2 sys_epoll_pwait2 + 442 common mount_setattr sys_mount_setattr ++443 common futex_wait sys_futex_wait ++444 common futex_wake sys_futex_wake +diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h +index 949788f5ba40..64ebdc1ec581 100644 +--- a/arch/arm64/include/asm/unistd.h ++++ b/arch/arm64/include/asm/unistd.h +@@ -38,7 +38,7 @@ + #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) + #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) + +-#define __NR_compat_syscalls 443 ++#define __NR_compat_syscalls 445 + #endif + + #define __ARCH_WANT_SYS_CLONE +diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h +index 3d874f624056..15c2cd5f1c95 100644 +--- a/arch/arm64/include/asm/unistd32.h ++++ b/arch/arm64/include/asm/unistd32.h +@@ -893,6 +893,10 @@ __SYSCALL(__NR_process_madvise, sys_process_madvise) + __SYSCALL(__NR_epoll_pwait2, compat_sys_epoll_pwait2) + #define __NR_mount_setattr 442 + __SYSCALL(__NR_mount_setattr, sys_mount_setattr) ++#define __NR_futex_wait 443 ++__SYSCALL(__NR_futex_wait, sys_futex_wait) ++#define __NR_futex_wake 444 ++__SYSCALL(__NR_futex_wake, sys_futex_wake) + + /* + * Please add new compat syscalls above this comment and update +diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl +index a1c9f496fca6..17d22509d780 100644 +--- a/arch/x86/entry/syscalls/syscall_32.tbl ++++ b/arch/x86/entry/syscalls/syscall_32.tbl +@@ -447,3 +447,5 @@ + 440 i386 process_madvise sys_process_madvise + 441 i386 epoll_pwait2 sys_epoll_pwait2 compat_sys_epoll_pwait2 + 442 i386 mount_setattr sys_mount_setattr ++443 i386 futex_wait sys_futex_wait ++444 i386 futex_wake sys_futex_wake +diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl +index 7bf01cbe582f..3336b5cd5bdb 100644 +--- a/arch/x86/entry/syscalls/syscall_64.tbl ++++ b/arch/x86/entry/syscalls/syscall_64.tbl +@@ -364,6 +364,8 @@ + 440 common process_madvise sys_process_madvise + 441 common epoll_pwait2 sys_epoll_pwait2 + 442 common mount_setattr sys_mount_setattr ++443 common futex_wait sys_futex_wait ++444 common futex_wake sys_futex_wake + + # + # Due to a historical design error, certain syscalls are numbered differently +diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h +index 2839dc9a7c01..352f69a2b94c 100644 +--- a/include/linux/syscalls.h ++++ b/include/linux/syscalls.h +@@ -619,6 +619,13 @@ asmlinkage long sys_get_robust_list(int pid, + asmlinkage long sys_set_robust_list(struct robust_list_head __user *head, + size_t len); + ++/* kernel/futex2.c */ ++asmlinkage long sys_futex_wait(void __user *uaddr, unsigned int val, ++ unsigned int flags, ++ struct __kernel_timespec __user *timo); ++asmlinkage long sys_futex_wake(void __user *uaddr, unsigned int nr_wake, ++ unsigned int flags); ++ + /* kernel/hrtimer.c */ + asmlinkage long sys_nanosleep(struct __kernel_timespec __user *rqtp, + struct __kernel_timespec __user *rmtp); +diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h +index ce58cff99b66..738315f148fa 100644 +--- a/include/uapi/asm-generic/unistd.h ++++ b/include/uapi/asm-generic/unistd.h +@@ -864,8 +864,14 @@ __SC_COMP(__NR_epoll_pwait2, sys_epoll_pwait2, compat_sys_epoll_pwait2) + #define __NR_mount_setattr 442 + __SYSCALL(__NR_mount_setattr, sys_mount_setattr) + ++#define __NR_futex_wait 443 ++__SYSCALL(__NR_futex_wait, sys_futex_wait) ++ ++#define __NR_futex_wake 444 ++__SYSCALL(__NR_futex_wake, sys_futex_wake) ++ + #undef __NR_syscalls +-#define __NR_syscalls 443 ++#define __NR_syscalls 445 + + /* + * 32 bit systems traditionally used different +diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h +index a89eb0accd5e..8d30f4b6d094 100644 +--- a/include/uapi/linux/futex.h ++++ b/include/uapi/linux/futex.h +@@ -41,6 +41,11 @@ + #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \ + FUTEX_PRIVATE_FLAG) + ++/* Size argument to futex2 syscall */ ++#define FUTEX_32 2 ++ ++#define FUTEX_SIZE_MASK 0x3 ++ + /* + * Support for robust futexes: the kernel cleans up held futexes at + * thread exit time. +diff --git a/init/Kconfig b/init/Kconfig +index 22946fe5ded9..0dce39965bfb 100644 +--- a/init/Kconfig ++++ b/init/Kconfig +@@ -1538,6 +1538,13 @@ config FUTEX + support for "fast userspace mutexes". The resulting kernel may not + run glibc-based applications correctly. + ++config FUTEX2 ++ bool "Enable futex2 support" if EXPERT ++ depends on FUTEX ++ default y ++ help ++ Support for futex2 interface. ++ + config FUTEX_PI + bool + depends on FUTEX && RT_MUTEXES +diff --git a/kernel/Makefile b/kernel/Makefile +index 320f1f3941b7..b6407f92c9af 100644 +--- a/kernel/Makefile ++++ b/kernel/Makefile +@@ -57,6 +57,7 @@ obj-$(CONFIG_PROFILING) += profile.o + obj-$(CONFIG_STACKTRACE) += stacktrace.o + obj-y += time/ + obj-$(CONFIG_FUTEX) += futex.o ++obj-$(CONFIG_FUTEX2) += futex2.o + obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o + obj-$(CONFIG_SMP) += smp.o + ifneq ($(CONFIG_SMP),y) +diff --git a/kernel/futex2.c b/kernel/futex2.c +new file mode 100644 +index 000000000000..d6a2efbfa488 +--- /dev/null ++++ b/kernel/futex2.c +@@ -0,0 +1,619 @@ ++// SPDX-License-Identifier: GPL-2.0-or-later ++/* ++ * futex2 system call interface by André Almeida ++ * ++ * Copyright 2021 Collabora Ltd. ++ * ++ * Based on original futex implementation by: ++ * (C) 2002 Rusty Russell, IBM ++ * (C) 2003, 2006 Ingo Molnar, Red Hat Inc. ++ * (C) 2003, 2004 Jamie Lokier ++ * (C) 2006 Thomas Gleixner, Timesys Corp. ++ * (C) 2007 Eric Dumazet ++ * (C) 2009 Darren Hart, IBM ++ */ ++ ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++ ++/** ++ * struct futex_key - Components to build unique key for a futex ++ * @pointer: Pointer to current->mm ++ * @index: Start address of the page containing futex ++ * @offset: Address offset of uaddr in a page ++ */ ++struct futex_key { ++ u64 pointer; ++ unsigned long index; ++ unsigned long offset; ++}; ++ ++/** ++ * struct futex_waiter - List entry for a waiter ++ * @uaddr: Virtual address of userspace futex ++ * @key: Information that uniquely identify a futex ++ * @list: List node struct ++ * @val: Expected value for this waiter ++ * @flags: Flags ++ * @bucket: Pointer to the bucket for this waiter ++ * @index: Index of waiter in futexv list ++ */ ++struct futex_waiter { ++ void __user *uaddr; ++ struct futex_key key; ++ struct list_head list; ++ unsigned int val; ++ unsigned int flags; ++ struct futex_bucket *bucket; ++ unsigned int index; ++}; ++ ++/** ++ * struct futex_waiter_head - List of futexes to be waited ++ * @task: Task to be awaken ++ * @hint: Was someone on this list awakened? ++ * @objects: List of futexes ++ */ ++struct futex_waiter_head { ++ struct task_struct *task; ++ bool hint; ++ struct futex_waiter objects[0]; ++}; ++ ++/** ++ * struct futex_bucket - A bucket of futex's hash table ++ * @waiters: Number of waiters in the bucket ++ * @lock: Bucket lock ++ * @list: List of waiters on this bucket ++ */ ++struct futex_bucket { ++ atomic_t waiters; ++ spinlock_t lock; ++ struct list_head list; ++}; ++ ++ ++/* Mask for futex2 flag operations */ ++#define FUTEX2_MASK (FUTEX_SIZE_MASK | FUTEX_CLOCK_REALTIME) ++ ++static struct futex_bucket *futex_table; ++static unsigned int futex2_hashsize; ++ ++/* ++ * Reflects a new waiter being added to the waitqueue. ++ */ ++static inline void bucket_inc_waiters(struct futex_bucket *bucket) ++{ ++#ifdef CONFIG_SMP ++ atomic_inc(&bucket->waiters); ++ /* ++ * Issue a barrier after adding so futex_wake() will see that the ++ * value had increased ++ */ ++ smp_mb__after_atomic(); ++#endif ++} ++ ++/* ++ * Reflects a waiter being removed from the waitqueue by wakeup ++ * paths. ++ */ ++static inline void bucket_dec_waiters(struct futex_bucket *bucket) ++{ ++#ifdef CONFIG_SMP ++ atomic_dec(&bucket->waiters); ++#endif ++} ++ ++/* ++ * Get the number of waiters in a bucket ++ */ ++static inline int bucket_get_waiters(struct futex_bucket *bucket) ++{ ++#ifdef CONFIG_SMP ++ /* ++ * Issue a barrier before reading so we get an updated value from ++ * futex_wait() ++ */ ++ smp_mb(); ++ return atomic_read(&bucket->waiters); ++#else ++ return 1; ++#endif ++} ++ ++/** ++ * futex_get_bucket - Check if the user address is valid, prepare internal ++ * data and calculate the hash ++ * @uaddr: futex user address ++ * @key: data that uniquely identifies a futex ++ * ++ * Return: address of bucket on success, error code otherwise ++ */ ++static struct futex_bucket *futex_get_bucket(void __user *uaddr, ++ struct futex_key *key) ++{ ++ uintptr_t address = (uintptr_t)uaddr; ++ u32 hash_key; ++ ++ /* Checking if uaddr is valid and accessible */ ++ if (unlikely(!IS_ALIGNED(address, sizeof(u32)))) ++ return ERR_PTR(-EINVAL); ++ if (unlikely(!access_ok(uaddr, sizeof(u32)))) ++ return ERR_PTR(-EFAULT); ++ ++ key->offset = address % PAGE_SIZE; ++ address -= key->offset; ++ key->pointer = (u64)address; ++ key->index = (unsigned long)current->mm; ++ ++ /* Generate hash key for this futex using uaddr and current->mm */ ++ hash_key = jhash2((u32 *)key, sizeof(*key) / sizeof(u32), 0); ++ ++ /* Since HASH_SIZE is 2^n, subtracting 1 makes a perfect bit mask */ ++ return &futex_table[hash_key & (futex2_hashsize - 1)]; ++} ++ ++/** ++ * futex_get_user - Get the userspace value on this address ++ * @uval: variable to store the value ++ * @uaddr: userspace address ++ * ++ * Check the comment at futex_enqueue() for more information. ++ */ ++static int futex_get_user(u32 *uval, u32 __user *uaddr) ++{ ++ int ret; ++ ++ pagefault_disable(); ++ ret = __get_user(*uval, uaddr); ++ pagefault_enable(); ++ ++ return ret; ++} ++ ++/** ++ * futex_setup_time - Prepare the timeout mechanism and start it. ++ * @timo: Timeout value from userspace ++ * @timeout: Pointer to hrtimer handler ++ * @flags: Flags from userspace, to decide which clockid to use ++ * ++ * Return: 0 on success, error code otherwise ++ */ ++static int futex_setup_time(struct __kernel_timespec __user *timo, ++ struct hrtimer_sleeper *timeout, ++ unsigned int flags) ++{ ++ ktime_t time; ++ struct timespec64 ts; ++ clockid_t clockid = (flags & FUTEX_CLOCK_REALTIME) ? ++ CLOCK_REALTIME : CLOCK_MONOTONIC; ++ ++ if (get_timespec64(&ts, timo)) ++ return -EFAULT; ++ ++ if (!timespec64_valid(&ts)) ++ return -EINVAL; ++ ++ time = timespec64_to_ktime(ts); ++ ++ hrtimer_init_sleeper(timeout, clockid, HRTIMER_MODE_ABS); ++ ++ hrtimer_set_expires(&timeout->timer, time); ++ ++ hrtimer_sleeper_start_expires(timeout, HRTIMER_MODE_ABS); ++ ++ return 0; ++} ++ ++/** ++ * futex_dequeue_multiple - Remove multiple futexes from hash table ++ * @futexv: list of waiters ++ * @nr: number of futexes to be removed ++ * ++ * This function is used if (a) something went wrong while enqueuing, and we ++ * need to undo our work (then nr <= nr_futexes) or (b) we woke up, and thus ++ * need to remove every waiter, check if some was indeed woken and return. ++ * Before removing a waiter, we check if it's on the list, since we have no ++ * clue who have been waken. ++ * ++ * Return: ++ * * -1 - If no futex was woken during the removal ++ * * 0>= - At least one futex was found woken, index of the last one ++ */ ++static int futex_dequeue_multiple(struct futex_waiter_head *futexv, unsigned int nr) ++{ ++ int i, ret = -1; ++ ++ for (i = 0; i < nr; i++) { ++ spin_lock(&futexv->objects[i].bucket->lock); ++ if (!list_empty(&futexv->objects[i].list)) { ++ list_del_init(&futexv->objects[i].list); ++ bucket_dec_waiters(futexv->objects[i].bucket); ++ } else { ++ ret = i; ++ } ++ spin_unlock(&futexv->objects[i].bucket->lock); ++ } ++ ++ return ret; ++} ++ ++/** ++ * futex_enqueue - Check the value and enqueue a futex on a wait list ++ * ++ * @futexv: List of futexes ++ * @nr_futexes: Number of futexes in the list ++ * @awakened: If a futex was awakened during enqueueing, store the index here ++ * ++ * Get the value from the userspace address and compares with the expected one. ++ * ++ * Getting the value from user futex address: ++ * ++ * Since we are in a hurry, we use a spin lock and we can't sleep. ++ * Try to get the value with page fault disabled (when enable, we might ++ * sleep). ++ * ++ * If we fail, we aren't sure if the address is invalid or is just a ++ * page fault. Then, release the lock (so we can sleep) and try to get ++ * the value with page fault enabled. In order to trigger a page fault ++ * handling, we just call __get_user() again. If we sleep with enqueued ++ * futexes, we might miss a wake, so dequeue everything before sleeping. ++ * ++ * If get_user succeeds, this mean that the address is valid and we do ++ * the work again. Since we just handled the page fault, the page is ++ * likely pinned in memory and we should be luckier this time and be ++ * able to get the value. If we fail anyway, we will try again. ++ * ++ * If even with page faults enabled we get and error, this means that ++ * the address is not valid and we return from the syscall. ++ * ++ * If we got an unexpected value or need to treat a page fault and realized that ++ * a futex was awakened, we can priority this and return success. ++ * ++ * In success, enqueue the futex in the correct bucket ++ * ++ * Return: ++ * * 1 - We were awake in the process and nothing is enqueued ++ * * 0 - Everything is enqueued and we are ready to sleep ++ * * 0< - Something went wrong, nothing is enqueued, return error code ++ */ ++static int futex_enqueue(struct futex_waiter_head *futexv, unsigned int nr_futexes, ++ int *awakened) ++{ ++ int i, ret; ++ u32 uval, val; ++ u32 __user *uaddr; ++ struct futex_bucket *bucket; ++ ++retry: ++ set_current_state(TASK_INTERRUPTIBLE); ++ ++ for (i = 0; i < nr_futexes; i++) { ++ uaddr = (u32 __user *)futexv->objects[i].uaddr; ++ val = (u32)futexv->objects[i].val; ++ ++ bucket = futexv->objects[i].bucket; ++ ++ bucket_inc_waiters(bucket); ++ spin_lock(&bucket->lock); ++ ++ ret = futex_get_user(&uval, uaddr); ++ ++ if (unlikely(ret)) { ++ spin_unlock(&bucket->lock); ++ ++ bucket_dec_waiters(bucket); ++ __set_current_state(TASK_RUNNING); ++ *awakened = futex_dequeue_multiple(futexv, i); ++ ++ if (*awakened >= 0) ++ return 1; ++ ++ if (__get_user(uval, uaddr)) ++ return -EFAULT; ++ ++ goto retry; ++ } ++ ++ if (uval != val) { ++ spin_unlock(&bucket->lock); ++ ++ bucket_dec_waiters(bucket); ++ __set_current_state(TASK_RUNNING); ++ *awakened = futex_dequeue_multiple(futexv, i); ++ ++ if (*awakened >= 0) ++ return 1; ++ ++ return -EAGAIN; ++ } ++ ++ list_add_tail(&futexv->objects[i].list, &bucket->list); ++ spin_unlock(&bucket->lock); ++ } ++ ++ return 0; ++} ++ ++/** ++ * __futex_wait - Enqueue the list of futexes and wait to be woken ++ * @futexv: List of futexes to wait ++ * @nr_futexes: Length of futexv ++ * @timeout: Pointer to timeout handler ++ * ++ * Return: ++ * * 0 >= - Hint of which futex woke us ++ * * 0 < - Error code ++ */ ++static int __futex_wait(struct futex_waiter_head *futexv, unsigned int nr_futexes, ++ struct hrtimer_sleeper *timeout) ++{ ++ int ret; ++ ++ while (1) { ++ int awakened = -1; ++ ++ ret = futex_enqueue(futexv, nr_futexes, &awakened); ++ ++ if (ret) { ++ if (awakened >= 0) ++ return awakened; ++ return ret; ++ } ++ ++ /* Before sleeping, check if someone was woken */ ++ if (!futexv->hint && (!timeout || timeout->task)) ++ freezable_schedule(); ++ ++ __set_current_state(TASK_RUNNING); ++ ++ /* ++ * One of those things triggered this wake: ++ * ++ * * We have been removed from the bucket. futex_wake() woke ++ * us. We just need to dequeue and return 0 to userspace. ++ * ++ * However, if no futex was dequeued by a futex_wake(): ++ * ++ * * If the there's a timeout and it has expired, ++ * return -ETIMEDOUT. ++ * ++ * * If there is a signal pending, something wants to kill our ++ * thread, return -ERESTARTSYS. ++ * ++ * * If there's no signal pending, it was a spurious wake ++ * (scheduler gave us a chance to do some work, even if we ++ * don't want to). We need to remove ourselves from the ++ * bucket and add again, to prevent losing wakeups in the ++ * meantime. ++ */ ++ ++ ret = futex_dequeue_multiple(futexv, nr_futexes); ++ ++ /* Normal wake */ ++ if (ret >= 0) ++ return ret; ++ ++ if (timeout && !timeout->task) ++ return -ETIMEDOUT; ++ ++ if (signal_pending(current)) ++ return -ERESTARTSYS; ++ ++ /* Spurious wake, do everything again */ ++ } ++} ++ ++/** ++ * futex_wait - Setup the timer (if there's one) and wait on a list of futexes ++ * @futexv: List of futexes ++ * @nr_futexes: Length of futexv ++ * @timo: Timeout ++ * @flags: Timeout flags ++ * ++ * Return: ++ * * 0 >= - Hint of which futex woke us ++ * * 0 < - Error code ++ */ ++static int futex_set_timer_and_wait(struct futex_waiter_head *futexv, ++ unsigned int nr_futexes, ++ struct __kernel_timespec __user *timo, ++ unsigned int flags) ++{ ++ struct hrtimer_sleeper timeout; ++ int ret; ++ ++ if (timo) { ++ ret = futex_setup_time(timo, &timeout, flags); ++ if (ret) ++ return ret; ++ } ++ ++ ret = __futex_wait(futexv, nr_futexes, timo ? &timeout : NULL); ++ ++ if (timo) ++ hrtimer_cancel(&timeout.timer); ++ ++ return ret; ++} ++ ++/** ++ * sys_futex_wait - Wait on a futex address if (*uaddr) == val ++ * @uaddr: User address of futex ++ * @val: Expected value of futex ++ * @flags: Specify the size of futex and the clockid ++ * @timo: Optional absolute timeout. ++ * ++ * The user thread is put to sleep, waiting for a futex_wake() at uaddr, if the ++ * value at *uaddr is the same as val (otherwise, the syscall returns ++ * immediately with -EAGAIN). ++ * ++ * Returns 0 on success, error code otherwise. ++ */ ++SYSCALL_DEFINE4(futex_wait, void __user *, uaddr, unsigned int, val, ++ unsigned int, flags, struct __kernel_timespec __user *, timo) ++{ ++ unsigned int size = flags & FUTEX_SIZE_MASK; ++ struct futex_waiter *waiter; ++ struct futex_waiter_head *futexv; ++ ++ /* Wrapper for a futexv_head of one element */ ++ struct { ++ struct futex_waiter_head futexv; ++ struct futex_waiter waiter; ++ } __packed wait_single; ++ ++ if (flags & ~FUTEX2_MASK) ++ return -EINVAL; ++ ++ if (size != FUTEX_32) ++ return -EINVAL; ++ ++ futexv = &wait_single.futexv; ++ futexv->task = current; ++ futexv->hint = false; ++ ++ waiter = &wait_single.waiter; ++ waiter->index = 0; ++ waiter->val = val; ++ waiter->uaddr = uaddr; ++ memset(&wait_single.waiter.key, 0, sizeof(struct futex_key)); ++ ++ INIT_LIST_HEAD(&waiter->list); ++ ++ /* Get an unlocked hash bucket */ ++ waiter->bucket = futex_get_bucket(uaddr, &waiter->key); ++ if (IS_ERR(waiter->bucket)) ++ return PTR_ERR(waiter->bucket); ++ ++ return futex_set_timer_and_wait(futexv, 1, timo, flags); ++} ++ ++/** ++ * futex_get_parent - For a given futex in a futexv list, get a pointer to the futexv ++ * @waiter: Address of futex in the list ++ * @index: Index of futex in the list ++ * ++ * Return: A pointer to its futexv struct ++ */ ++static inline struct futex_waiter_head *futex_get_parent(uintptr_t waiter, ++ unsigned int index) ++{ ++ uintptr_t parent = waiter - sizeof(struct futex_waiter_head) ++ - (uintptr_t)(index * sizeof(struct futex_waiter)); ++ ++ return (struct futex_waiter_head *)parent; ++} ++ ++/** ++ * futex_mark_wake - Find the task to be wake and add it in wake queue ++ * @waiter: Waiter to be wake ++ * @bucket: Bucket to be decremented ++ * @wake_q: Wake queue to insert the task ++ */ ++static void futex_mark_wake(struct futex_waiter *waiter, ++ struct futex_bucket *bucket, ++ struct wake_q_head *wake_q) ++{ ++ struct task_struct *task; ++ struct futex_waiter_head *parent = futex_get_parent((uintptr_t)waiter, ++ waiter->index); ++ ++ lockdep_assert_held(&bucket->lock); ++ parent->hint = true; ++ task = parent->task; ++ get_task_struct(task); ++ list_del_init(&waiter->list); ++ wake_q_add_safe(wake_q, task); ++ bucket_dec_waiters(bucket); ++} ++ ++static inline bool futex_match(struct futex_key key1, struct futex_key key2) ++{ ++ return (key1.index == key2.index && ++ key1.pointer == key2.pointer && ++ key1.offset == key2.offset); ++} ++ ++/** ++ * sys_futex_wake - Wake a number of futexes waiting on an address ++ * @uaddr: Address of futex to be woken up ++ * @nr_wake: Number of futexes waiting in uaddr to be woken up ++ * @flags: Flags for size and shared ++ * ++ * Wake `nr_wake` threads waiting at uaddr. ++ * ++ * Returns the number of woken threads on success, error code otherwise. ++ */ ++SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, ++ unsigned int, flags) ++{ ++ unsigned int size = flags & FUTEX_SIZE_MASK; ++ struct futex_waiter waiter, *aux, *tmp; ++ struct futex_bucket *bucket; ++ DEFINE_WAKE_Q(wake_q); ++ int ret = 0; ++ ++ if (flags & ~FUTEX2_MASK) ++ return -EINVAL; ++ ++ if (size != FUTEX_32) ++ return -EINVAL; ++ ++ bucket = futex_get_bucket(uaddr, &waiter.key); ++ if (IS_ERR(bucket)) ++ return PTR_ERR(bucket); ++ ++ if (!bucket_get_waiters(bucket) || !nr_wake) ++ return 0; ++ ++ spin_lock(&bucket->lock); ++ list_for_each_entry_safe(aux, tmp, &bucket->list, list) { ++ if (futex_match(waiter.key, aux->key)) { ++ futex_mark_wake(aux, bucket, &wake_q); ++ if (++ret >= nr_wake) ++ break; ++ } ++ } ++ spin_unlock(&bucket->lock); ++ ++ wake_up_q(&wake_q); ++ ++ return ret; ++} ++ ++static int __init futex2_init(void) ++{ ++ int i; ++ unsigned int futex_shift; ++ ++#if CONFIG_BASE_SMALL ++ futex2_hashsize = 16; ++#else ++ futex2_hashsize = roundup_pow_of_two(256 * num_possible_cpus()); ++#endif ++ ++ futex_table = alloc_large_system_hash("futex2", sizeof(struct futex_bucket), ++ futex2_hashsize, 0, ++ futex2_hashsize < 256 ? HASH_SMALL : 0, ++ &futex_shift, NULL, ++ futex2_hashsize, futex2_hashsize); ++ futex2_hashsize = 1UL << futex_shift; ++ ++ BUG_ON(!is_power_of_2(futex2_hashsize)); ++ ++ for (i = 0; i < futex2_hashsize; i++) { ++ INIT_LIST_HEAD(&futex_table[i].list); ++ spin_lock_init(&futex_table[i].lock); ++ atomic_set(&futex_table[i].waiters, 0); ++ } ++ ++ return 0; ++} ++core_initcall(futex2_init); +diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c +index 19aa806890d5..27ef83ca8a9d 100644 +--- a/kernel/sys_ni.c ++++ b/kernel/sys_ni.c +@@ -150,6 +150,10 @@ COND_SYSCALL_COMPAT(set_robust_list); + COND_SYSCALL(get_robust_list); + COND_SYSCALL_COMPAT(get_robust_list); + ++/* kernel/futex2.c */ ++COND_SYSCALL(futex_wait); ++COND_SYSCALL(futex_wake); ++ + /* kernel/hrtimer.c */ + + /* kernel/itimer.c */ +diff --git a/tools/include/uapi/asm-generic/unistd.h b/tools/include/uapi/asm-generic/unistd.h +index ce58cff99b66..738315f148fa 100644 +--- a/tools/include/uapi/asm-generic/unistd.h ++++ b/tools/include/uapi/asm-generic/unistd.h +@@ -864,8 +864,14 @@ __SC_COMP(__NR_epoll_pwait2, sys_epoll_pwait2, compat_sys_epoll_pwait2) + #define __NR_mount_setattr 442 + __SYSCALL(__NR_mount_setattr, sys_mount_setattr) + ++#define __NR_futex_wait 443 ++__SYSCALL(__NR_futex_wait, sys_futex_wait) ++ ++#define __NR_futex_wake 444 ++__SYSCALL(__NR_futex_wake, sys_futex_wake) ++ + #undef __NR_syscalls +-#define __NR_syscalls 443 ++#define __NR_syscalls 445 + + /* + * 32 bit systems traditionally used different +diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl +index 78672124d28b..15d2b89b6ad7 100644 +--- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl ++++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl +@@ -363,6 +363,8 @@ + 439 common faccessat2 sys_faccessat2 + 440 common process_madvise sys_process_madvise + 441 common epoll_pwait2 sys_epoll_pwait2 ++442 common futex_wait sys_futex_wait ++443 common futex_wake sys_futex_wake + + # + # Due to a historical design error, certain syscalls are numbered differently +-- +GitLab + +From 5e0a8c1ff68778e373871b741a54554e89f0b8fe Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:01 -0300 +Subject: [PATCH] futex2: Add support for shared futexes +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Add support for shared futexes for cross-process resources. This design +relies on the same approach done in old futex to create an unique id for +file-backed shared memory, by using a counter at struct inode. + +There are two types of futexes: private and shared ones. The private are futexes +meant to be used by threads that shares the same memory space, are easier to be +uniquely identified an thus can have some performance optimization. The elements +for identifying one are: the start address of the page where the address is, +the address offset within the page and the current->mm pointer. + +Now, for uniquely identifying shared futex: + +- If the page containing the user address is an anonymous page, we can + just use the same data used for private futexes (the start address of + the page, the address offset within the page and the current->mm + pointer) that will be enough for uniquely identifying such futex. We + also set one bit at the key to differentiate if a private futex is + used on the same address (mixing shared and private calls are not + allowed). + +- If the page is file-backed, current->mm maybe isn't the same one for + every user of this futex, so we need to use other data: the + page->index, an UUID for the struct inode and the offset within the + page. + +Note that members of futex_key doesn't have any particular meaning after they +are part of the struct - they are just bytes to identify a futex. Given that, +we don't need to use a particular name or type that matches the original data, +we only need to care about the bitsize of each component and make both private +and shared data fit in the same memory space. + +Signed-off-by: André Almeida +--- + fs/inode.c | 1 + + include/linux/fs.h | 1 + + include/uapi/linux/futex.h | 2 + + kernel/futex2.c | 222 ++++++++++++++++++++++++++++++++++++- + 4 files changed, 220 insertions(+), 6 deletions(-) + +diff --git a/fs/inode.c b/fs/inode.c +index a047ab306f9a..c5e1dd13fd40 100644 +--- a/fs/inode.c ++++ b/fs/inode.c +@@ -139,6 +139,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode) + inode->i_blkbits = sb->s_blocksize_bits; + inode->i_flags = 0; + atomic64_set(&inode->i_sequence, 0); ++ atomic64_set(&inode->i_sequence2, 0); + atomic_set(&inode->i_count, 1); + inode->i_op = &empty_iops; + inode->i_fop = &no_open_fops; +diff --git a/include/linux/fs.h b/include/linux/fs.h +index ec8f3ddf4a6a..33683ff94cb3 100644 +--- a/include/linux/fs.h ++++ b/include/linux/fs.h +@@ -683,6 +683,7 @@ struct inode { + }; + atomic64_t i_version; + atomic64_t i_sequence; /* see futex */ ++ atomic64_t i_sequence2; /* see futex2 */ + atomic_t i_count; + atomic_t i_dio_count; + atomic_t i_writecount; +diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h +index 8d30f4b6d094..70ea66fffb1c 100644 +--- a/include/uapi/linux/futex.h ++++ b/include/uapi/linux/futex.h +@@ -46,6 +46,8 @@ + + #define FUTEX_SIZE_MASK 0x3 + ++#define FUTEX_SHARED_FLAG 8 ++ + /* + * Support for robust futexes: the kernel cleans up held futexes at + * thread exit time. +diff --git a/kernel/futex2.c b/kernel/futex2.c +index d6a2efbfa488..69866f98f287 100644 +--- a/kernel/futex2.c ++++ b/kernel/futex2.c +@@ -14,8 +14,10 @@ + */ + + #include ++#include + #include + #include ++#include + #include + #include + #include +@@ -23,8 +25,8 @@ + + /** + * struct futex_key - Components to build unique key for a futex +- * @pointer: Pointer to current->mm +- * @index: Start address of the page containing futex ++ * @pointer: Pointer to current->mm or inode's UUID for file backed futexes ++ * @index: Start address of the page containing futex or index of the page + * @offset: Address offset of uaddr in a page + */ + struct futex_key { +@@ -79,7 +81,12 @@ struct futex_bucket { + + + /* Mask for futex2 flag operations */ +-#define FUTEX2_MASK (FUTEX_SIZE_MASK | FUTEX_CLOCK_REALTIME) ++#define FUTEX2_MASK (FUTEX_SIZE_MASK | FUTEX_CLOCK_REALTIME | FUTEX_SHARED_FLAG) ++ ++#define is_object_shared ((futexv->objects[i].flags & FUTEX_SHARED_FLAG) ? true : false) ++ ++#define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */ ++#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */ + + static struct futex_bucket *futex_table; + static unsigned int futex2_hashsize; +@@ -127,16 +134,200 @@ static inline int bucket_get_waiters(struct futex_bucket *bucket) + #endif + } + ++/** ++ * futex_get_inode_uuid - Gets an UUID for an inode ++ * @inode: inode to get UUID ++ * ++ * Generate a machine wide unique identifier for this inode. ++ * ++ * This relies on u64 not wrapping in the life-time of the machine; which with ++ * 1ns resolution means almost 585 years. ++ * ++ * This further relies on the fact that a well formed program will not unmap ++ * the file while it has a (shared) futex waiting on it. This mapping will have ++ * a file reference which pins the mount and inode. ++ * ++ * If for some reason an inode gets evicted and read back in again, it will get ++ * a new sequence number and will _NOT_ match, even though it is the exact same ++ * file. ++ * ++ * It is important that match_futex() will never have a false-positive, esp. ++ * for PI futexes that can mess up the state. The above argues that false-negatives ++ * are only possible for malformed programs. ++ * ++ * Returns: UUID for the given inode ++ */ ++static u64 futex_get_inode_uuid(struct inode *inode) ++{ ++ static atomic64_t i_seq; ++ u64 old; ++ ++ /* Does the inode already have a sequence number? */ ++ old = atomic64_read(&inode->i_sequence2); ++ ++ if (likely(old)) ++ return old; ++ ++ for (;;) { ++ u64 new = atomic64_add_return(1, &i_seq); ++ ++ if (WARN_ON_ONCE(!new)) ++ continue; ++ ++ old = atomic64_cmpxchg_relaxed(&inode->i_sequence2, 0, new); ++ if (old) ++ return old; ++ return new; ++ } ++} ++ ++/** ++ * futex_get_shared_key - Get a key for a shared futex ++ * @address: Futex memory address ++ * @mm: Current process mm_struct pointer ++ * @key: Key struct to be filled ++ * ++ * Returns: 0 on success, error code otherwise ++ */ ++static int futex_get_shared_key(uintptr_t address, struct mm_struct *mm, ++ struct futex_key *key) ++{ ++ int ret; ++ struct page *page, *tail; ++ struct address_space *mapping; ++ ++again: ++ ret = get_user_pages_fast(address, 1, 0, &page); ++ if (ret < 0) ++ return ret; ++ ++ /* ++ * The treatment of mapping from this point on is critical. The page ++ * lock protects many things but in this context the page lock ++ * stabilizes mapping, prevents inode freeing in the shared ++ * file-backed region case and guards against movement to swap cache. ++ * ++ * Strictly speaking the page lock is not needed in all cases being ++ * considered here and page lock forces unnecessarily serialization ++ * From this point on, mapping will be re-verified if necessary and ++ * page lock will be acquired only if it is unavoidable ++ * ++ * Mapping checks require the head page for any compound page so the ++ * head page and mapping is looked up now. For anonymous pages, it ++ * does not matter if the page splits in the future as the key is ++ * based on the address. For filesystem-backed pages, the tail is ++ * required as the index of the page determines the key. For ++ * base pages, there is no tail page and tail == page. ++ */ ++ tail = page; ++ page = compound_head(page); ++ mapping = READ_ONCE(page->mapping); ++ ++ /* ++ * If page->mapping is NULL, then it cannot be a PageAnon ++ * page; but it might be the ZERO_PAGE or in the gate area or ++ * in a special mapping (all cases which we are happy to fail); ++ * or it may have been a good file page when get_user_pages_fast ++ * found it, but truncated or holepunched or subjected to ++ * invalidate_complete_page2 before we got the page lock (also ++ * cases which we are happy to fail). And we hold a reference, ++ * so refcount care in invalidate_complete_page's remove_mapping ++ * prevents drop_caches from setting mapping to NULL beneath us. ++ * ++ * The case we do have to guard against is when memory pressure made ++ * shmem_writepage move it from filecache to swapcache beneath us: ++ * an unlikely race, but we do need to retry for page->mapping. ++ */ ++ if (unlikely(!mapping)) { ++ int shmem_swizzled; ++ ++ /* ++ * Page lock is required to identify which special case above ++ * applies. If this is really a shmem page then the page lock ++ * will prevent unexpected transitions. ++ */ ++ lock_page(page); ++ shmem_swizzled = PageSwapCache(page) || page->mapping; ++ unlock_page(page); ++ put_page(page); ++ ++ if (shmem_swizzled) ++ goto again; ++ ++ return -EFAULT; ++ } ++ ++ /* ++ * Private mappings are handled in a simple way. ++ * ++ * If the futex key is stored on an anonymous page, then the associated ++ * object is the mm which is implicitly pinned by the calling process. ++ * ++ * NOTE: When userspace waits on a MAP_SHARED mapping, even if ++ * it's a read-only handle, it's expected that futexes attach to ++ * the object not the particular process. ++ */ ++ if (PageAnon(page)) { ++ key->offset |= FUT_OFF_MMSHARED; ++ } else { ++ struct inode *inode; ++ ++ /* ++ * The associated futex object in this case is the inode and ++ * the page->mapping must be traversed. Ordinarily this should ++ * be stabilised under page lock but it's not strictly ++ * necessary in this case as we just want to pin the inode, not ++ * update the radix tree or anything like that. ++ * ++ * The RCU read lock is taken as the inode is finally freed ++ * under RCU. If the mapping still matches expectations then the ++ * mapping->host can be safely accessed as being a valid inode. ++ */ ++ rcu_read_lock(); ++ ++ if (READ_ONCE(page->mapping) != mapping) { ++ rcu_read_unlock(); ++ put_page(page); ++ ++ goto again; ++ } ++ ++ inode = READ_ONCE(mapping->host); ++ if (!inode) { ++ rcu_read_unlock(); ++ put_page(page); ++ ++ goto again; ++ } ++ ++ key->pointer = futex_get_inode_uuid(inode); ++ key->index = (unsigned long)basepage_index(tail); ++ key->offset |= FUT_OFF_INODE; ++ ++ rcu_read_unlock(); ++ } ++ ++ put_page(page); ++ ++ return 0; ++} ++ + /** + * futex_get_bucket - Check if the user address is valid, prepare internal + * data and calculate the hash + * @uaddr: futex user address + * @key: data that uniquely identifies a futex ++ * @shared: is this a shared futex? ++ * ++ * For private futexes, each uaddr will be unique for a given mm_struct, and it ++ * won't be freed for the life time of the process. For shared futexes, check ++ * futex_get_shared_key(). + * + * Return: address of bucket on success, error code otherwise + */ + static struct futex_bucket *futex_get_bucket(void __user *uaddr, +- struct futex_key *key) ++ struct futex_key *key, ++ bool shared) + { + uintptr_t address = (uintptr_t)uaddr; + u32 hash_key; +@@ -152,6 +343,9 @@ static struct futex_bucket *futex_get_bucket(void __user *uaddr, + key->pointer = (u64)address; + key->index = (unsigned long)current->mm; + ++ if (shared) ++ futex_get_shared_key(address, current->mm, key); ++ + /* Generate hash key for this futex using uaddr and current->mm */ + hash_key = jhash2((u32 *)key, sizeof(*key) / sizeof(u32), 0); + +@@ -289,6 +483,7 @@ static int futex_enqueue(struct futex_waiter_head *futexv, unsigned int nr_futex + int i, ret; + u32 uval, val; + u32 __user *uaddr; ++ bool retry = false; + struct futex_bucket *bucket; + + retry: +@@ -298,6 +493,18 @@ static int futex_enqueue(struct futex_waiter_head *futexv, unsigned int nr_futex + uaddr = (u32 __user *)futexv->objects[i].uaddr; + val = (u32)futexv->objects[i].val; + ++ if (is_object_shared && retry) { ++ struct futex_bucket *tmp = ++ futex_get_bucket((void __user *)uaddr, ++ &futexv->objects[i].key, true); ++ if (IS_ERR(tmp)) { ++ __set_current_state(TASK_RUNNING); ++ futex_dequeue_multiple(futexv, i); ++ return PTR_ERR(tmp); ++ } ++ futexv->objects[i].bucket = tmp; ++ } ++ + bucket = futexv->objects[i].bucket; + + bucket_inc_waiters(bucket); +@@ -318,6 +525,7 @@ static int futex_enqueue(struct futex_waiter_head *futexv, unsigned int nr_futex + if (__get_user(uval, uaddr)) + return -EFAULT; + ++ retry = true; + goto retry; + } + +@@ -459,6 +667,7 @@ static int futex_set_timer_and_wait(struct futex_waiter_head *futexv, + SYSCALL_DEFINE4(futex_wait, void __user *, uaddr, unsigned int, val, + unsigned int, flags, struct __kernel_timespec __user *, timo) + { ++ bool shared = (flags & FUTEX_SHARED_FLAG) ? true : false; + unsigned int size = flags & FUTEX_SIZE_MASK; + struct futex_waiter *waiter; + struct futex_waiter_head *futexv; +@@ -488,7 +697,7 @@ SYSCALL_DEFINE4(futex_wait, void __user *, uaddr, unsigned int, val, + INIT_LIST_HEAD(&waiter->list); + + /* Get an unlocked hash bucket */ +- waiter->bucket = futex_get_bucket(uaddr, &waiter->key); ++ waiter->bucket = futex_get_bucket(uaddr, &waiter->key, shared); + if (IS_ERR(waiter->bucket)) + return PTR_ERR(waiter->bucket); + +@@ -554,6 +763,7 @@ static inline bool futex_match(struct futex_key key1, struct futex_key key2) + SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, + unsigned int, flags) + { ++ bool shared = (flags & FUTEX_SHARED_FLAG) ? true : false; + unsigned int size = flags & FUTEX_SIZE_MASK; + struct futex_waiter waiter, *aux, *tmp; + struct futex_bucket *bucket; +@@ -566,7 +776,7 @@ SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, + if (size != FUTEX_32) + return -EINVAL; + +- bucket = futex_get_bucket(uaddr, &waiter.key); ++ bucket = futex_get_bucket(uaddr, &waiter.key, shared); + if (IS_ERR(bucket)) + return PTR_ERR(bucket); + +-- +GitLab + +From 9ac7e0f5c6a4f0e56d0e974e21ec4fa09d899be1 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:00 -0300 +Subject: [PATCH] futex2: Implement vectorized wait +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Add support to wait on multiple futexes. This is the interface +implemented by this syscall: + +futex_waitv(struct futex_waitv *waiters, unsigned int nr_futexes, + unsigned int flags, struct timespec *timo) + +struct futex_waitv { + void *uaddr; + unsigned int val; + unsigned int flags; +}; + +Given an array of struct futex_waitv, wait on each uaddr. The thread +wakes if a futex_wake() is performed at any uaddr. The syscall returns +immediately if any waiter has *uaddr != val. *timo is an optional +timeout value for the operation. The flags argument of the syscall +should be used solely for specifying the timeout as realtime, if needed. +Flags for shared futexes, sizes, etc. should be used on the individual +flags of each waiter. + +Returns the array index of one of the awakened futexes. There’s no given +information of how many were awakened, or any particular attribute of it +(if it’s the first awakened, if it is of the smaller index...). + +Signed-off-by: André Almeida +--- + arch/arm/tools/syscall.tbl | 1 + + arch/x86/entry/syscalls/syscall_32.tbl | 1 + + arch/x86/entry/syscalls/syscall_64.tbl | 1 + + include/linux/compat.h | 11 ++ + include/linux/syscalls.h | 4 + + include/uapi/asm-generic/unistd.h | 5 +- + include/uapi/linux/futex.h | 14 ++ + kernel/futex2.c | 177 ++++++++++++++++++ + kernel/sys_ni.c | 1 + + tools/include/uapi/asm-generic/unistd.h | 5 +- + .../arch/x86/entry/syscalls/syscall_64.tbl | 1 + + 11 files changed, 219 insertions(+), 2 deletions(-) + +diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl +index 2bf93c69e00a..f9b55f2ea444 100644 +--- a/arch/arm/tools/syscall.tbl ++++ b/arch/arm/tools/syscall.tbl +@@ -458,3 +458,4 @@ + 442 common mount_setattr sys_mount_setattr + 443 common futex_wait sys_futex_wait + 444 common futex_wake sys_futex_wake ++445 common futex_waitv sys_futex_waitv +diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl +index 17d22509d780..4bc546c841b0 100644 +--- a/arch/x86/entry/syscalls/syscall_32.tbl ++++ b/arch/x86/entry/syscalls/syscall_32.tbl +@@ -449,3 +449,4 @@ + 442 i386 mount_setattr sys_mount_setattr + 443 i386 futex_wait sys_futex_wait + 444 i386 futex_wake sys_futex_wake ++445 i386 futex_waitv sys_futex_waitv compat_sys_futex_waitv +diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl +index 3336b5cd5bdb..a715e88e3d6d 100644 +--- a/arch/x86/entry/syscalls/syscall_64.tbl ++++ b/arch/x86/entry/syscalls/syscall_64.tbl +@@ -366,6 +366,7 @@ + 442 common mount_setattr sys_mount_setattr + 443 common futex_wait sys_futex_wait + 444 common futex_wake sys_futex_wake ++445 common futex_waitv sys_futex_waitv + + # + # Due to a historical design error, certain syscalls are numbered differently +diff --git a/include/linux/compat.h b/include/linux/compat.h +index 6e65be753603..041d18174350 100644 +--- a/include/linux/compat.h ++++ b/include/linux/compat.h +@@ -365,6 +365,12 @@ struct compat_robust_list_head { + compat_uptr_t list_op_pending; + }; + ++struct compat_futex_waitv { ++ compat_uptr_t uaddr; ++ compat_uint_t val; ++ compat_uint_t flags; ++}; ++ + #ifdef CONFIG_COMPAT_OLD_SIGACTION + struct compat_old_sigaction { + compat_uptr_t sa_handler; +@@ -654,6 +660,11 @@ asmlinkage long + compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, + compat_size_t __user *len_ptr); + ++/* kernel/futex2.c */ ++asmlinkage long compat_sys_futex_waitv(struct compat_futex_waitv *waiters, ++ compat_uint_t nr_futexes, compat_uint_t flags, ++ struct __kernel_timespec __user *timo); ++ + /* kernel/itimer.c */ + asmlinkage long compat_sys_getitimer(int which, + struct old_itimerval32 __user *it); +diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h +index 352f69a2b94c..48e96fe7d8f6 100644 +--- a/include/linux/syscalls.h ++++ b/include/linux/syscalls.h +@@ -69,6 +69,7 @@ struct io_uring_params; + struct clone_args; + struct open_how; + struct mount_attr; ++struct futex_waitv; + + #include + #include +@@ -625,6 +626,9 @@ asmlinkage long sys_futex_wait(void __user *uaddr, unsigned int val, + struct __kernel_timespec __user *timo); + asmlinkage long sys_futex_wake(void __user *uaddr, unsigned int nr_wake, + unsigned int flags); ++asmlinkage long sys_futex_waitv(struct futex_waitv __user *waiters, ++ unsigned int nr_futexes, unsigned int flags, ++ struct __kernel_timespec __user *timo); + + /* kernel/hrtimer.c */ + asmlinkage long sys_nanosleep(struct __kernel_timespec __user *rqtp, +diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h +index 738315f148fa..2a6adca37fe9 100644 +--- a/include/uapi/asm-generic/unistd.h ++++ b/include/uapi/asm-generic/unistd.h +@@ -870,8 +870,11 @@ __SYSCALL(__NR_futex_wait, sys_futex_wait) + #define __NR_futex_wake 444 + __SYSCALL(__NR_futex_wake, sys_futex_wake) + ++#define __NR_futex_waitv 445 ++__SC_COMP(__NR_futex_waitv, sys_futex_waitv, compat_sys_futex_waitv) ++ + #undef __NR_syscalls +-#define __NR_syscalls 445 ++#define __NR_syscalls 446 + + /* + * 32 bit systems traditionally used different +diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h +index 70ea66fffb1c..3216aee015d2 100644 +--- a/include/uapi/linux/futex.h ++++ b/include/uapi/linux/futex.h +@@ -48,6 +48,20 @@ + + #define FUTEX_SHARED_FLAG 8 + ++#define FUTEX_WAITV_MAX 128 ++ ++/** ++ * struct futex_waitv - A waiter for vectorized wait ++ * @uaddr: User address to wait on ++ * @val: Expected value at uaddr ++ * @flags: Flags for this waiter ++ */ ++struct futex_waitv { ++ void __user *uaddr; ++ unsigned int val; ++ unsigned int flags; ++}; ++ + /* + * Support for robust futexes: the kernel cleans up held futexes at + * thread exit time. +diff --git a/kernel/futex2.c b/kernel/futex2.c +index 69866f98f287..3290e51695eb 100644 +--- a/kernel/futex2.c ++++ b/kernel/futex2.c +@@ -83,6 +83,12 @@ struct futex_bucket { + /* Mask for futex2 flag operations */ + #define FUTEX2_MASK (FUTEX_SIZE_MASK | FUTEX_CLOCK_REALTIME | FUTEX_SHARED_FLAG) + ++/* Mask for sys_futex_waitv flag */ ++#define FUTEXV_MASK (FUTEX_CLOCK_REALTIME) ++ ++/* Mask for each futex in futex_waitv list */ ++#define FUTEXV_WAITER_MASK (FUTEX_SIZE_MASK | FUTEX_SHARED_FLAG) ++ + #define is_object_shared ((futexv->objects[i].flags & FUTEX_SHARED_FLAG) ? true : false) + + #define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */ +@@ -704,6 +710,177 @@ SYSCALL_DEFINE4(futex_wait, void __user *, uaddr, unsigned int, val, + return futex_set_timer_and_wait(futexv, 1, timo, flags); + } + ++#ifdef CONFIG_COMPAT ++/** ++ * compat_futex_parse_waitv - Parse a waitv array from userspace ++ * @futexv: Kernel side list of waiters to be filled ++ * @uwaitv: Userspace list to be parsed ++ * @nr_futexes: Length of futexv ++ * ++ * Return: Error code on failure, pointer to a prepared futexv otherwise ++ */ ++static int compat_futex_parse_waitv(struct futex_waiter_head *futexv, ++ struct compat_futex_waitv __user *uwaitv, ++ unsigned int nr_futexes) ++{ ++ struct futex_bucket *bucket; ++ struct compat_futex_waitv waitv; ++ unsigned int i; ++ ++ for (i = 0; i < nr_futexes; i++) { ++ if (copy_from_user(&waitv, &uwaitv[i], sizeof(waitv))) ++ return -EFAULT; ++ ++ if ((waitv.flags & ~FUTEXV_WAITER_MASK) || ++ (waitv.flags & FUTEX_SIZE_MASK) != FUTEX_32) ++ return -EINVAL; ++ ++ futexv->objects[i].key.pointer = 0; ++ futexv->objects[i].flags = waitv.flags; ++ futexv->objects[i].uaddr = compat_ptr(waitv.uaddr); ++ futexv->objects[i].val = waitv.val; ++ futexv->objects[i].index = i; ++ ++ bucket = futex_get_bucket(compat_ptr(waitv.uaddr), ++ &futexv->objects[i].key, ++ is_object_shared); ++ ++ if (IS_ERR(bucket)) ++ return PTR_ERR(bucket); ++ ++ futexv->objects[i].bucket = bucket; ++ ++ INIT_LIST_HEAD(&futexv->objects[i].list); ++ } ++ ++ return 0; ++} ++ ++COMPAT_SYSCALL_DEFINE4(futex_waitv, struct compat_futex_waitv __user *, waiters, ++ unsigned int, nr_futexes, unsigned int, flags, ++ struct __kernel_timespec __user *, timo) ++{ ++ struct futex_waiter_head *futexv; ++ int ret; ++ ++ if (flags & ~FUTEXV_MASK) ++ return -EINVAL; ++ ++ if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters) ++ return -EINVAL; ++ ++ futexv = kmalloc((sizeof(struct futex_waiter) * nr_futexes) + ++ sizeof(*futexv), GFP_KERNEL); ++ if (!futexv) ++ return -ENOMEM; ++ ++ futexv->hint = false; ++ futexv->task = current; ++ ++ ret = compat_futex_parse_waitv(futexv, waiters, nr_futexes); ++ ++ if (!ret) ++ ret = futex_set_timer_and_wait(futexv, nr_futexes, timo, flags); ++ ++ kfree(futexv); ++ ++ return ret; ++} ++#endif ++ ++/** ++ * futex_parse_waitv - Parse a waitv array from userspace ++ * @futexv: Kernel side list of waiters to be filled ++ * @uwaitv: Userspace list to be parsed ++ * @nr_futexes: Length of futexv ++ * ++ * Return: Error code on failure, pointer to a prepared futexv otherwise ++ */ ++static int futex_parse_waitv(struct futex_waiter_head *futexv, ++ struct futex_waitv __user *uwaitv, ++ unsigned int nr_futexes) ++{ ++ struct futex_bucket *bucket; ++ struct futex_waitv waitv; ++ unsigned int i; ++ ++ for (i = 0; i < nr_futexes; i++) { ++ if (copy_from_user(&waitv, &uwaitv[i], sizeof(waitv))) ++ return -EFAULT; ++ ++ if ((waitv.flags & ~FUTEXV_WAITER_MASK) || ++ (waitv.flags & FUTEX_SIZE_MASK) != FUTEX_32) ++ return -EINVAL; ++ ++ futexv->objects[i].key.pointer = 0; ++ futexv->objects[i].flags = waitv.flags; ++ futexv->objects[i].uaddr = waitv.uaddr; ++ futexv->objects[i].val = waitv.val; ++ futexv->objects[i].index = i; ++ ++ bucket = futex_get_bucket(waitv.uaddr, &futexv->objects[i].key, ++ is_object_shared); ++ ++ if (IS_ERR(bucket)) ++ return PTR_ERR(bucket); ++ ++ futexv->objects[i].bucket = bucket; ++ ++ INIT_LIST_HEAD(&futexv->objects[i].list); ++ } ++ ++ return 0; ++} ++ ++/** ++ * sys_futex_waitv - Wait on a list of futexes ++ * @waiters: List of futexes to wait on ++ * @nr_futexes: Length of futexv ++ * @flags: Flag for timeout (monotonic/realtime) ++ * @timo: Optional absolute timeout. ++ * ++ * Given an array of `struct futex_waitv`, wait on each uaddr. The thread wakes ++ * if a futex_wake() is performed at any uaddr. The syscall returns immediately ++ * if any waiter has *uaddr != val. *timo is an optional timeout value for the ++ * operation. Each waiter has individual flags. The `flags` argument for the ++ * syscall should be used solely for specifying the timeout as realtime, if ++ * needed. Flags for shared futexes, sizes, etc. should be used on the ++ * individual flags of each waiter. ++ * ++ * Returns the array index of one of the awaken futexes. There's no given ++ * information of how many were awakened, or any particular attribute of it (if ++ * it's the first awakened, if it is of the smaller index...). ++ */ ++SYSCALL_DEFINE4(futex_waitv, struct futex_waitv __user *, waiters, ++ unsigned int, nr_futexes, unsigned int, flags, ++ struct __kernel_timespec __user *, timo) ++{ ++ struct futex_waiter_head *futexv; ++ int ret; ++ ++ if (flags & ~FUTEXV_MASK) ++ return -EINVAL; ++ ++ if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters) ++ return -EINVAL; ++ ++ futexv = kmalloc((sizeof(struct futex_waiter) * nr_futexes) + ++ sizeof(*futexv), GFP_KERNEL); ++ if (!futexv) ++ return -ENOMEM; ++ ++ futexv->hint = false; ++ futexv->task = current; ++ ++ ret = futex_parse_waitv(futexv, waiters, nr_futexes); ++ if (!ret) ++ ret = futex_set_timer_and_wait(futexv, nr_futexes, timo, flags); ++ ++ kfree(futexv); ++ ++ return ret; ++} ++ + /** + * futex_get_parent - For a given futex in a futexv list, get a pointer to the futexv + * @waiter: Address of futex in the list +diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c +index 27ef83ca8a9d..977890c58ab5 100644 +--- a/kernel/sys_ni.c ++++ b/kernel/sys_ni.c +@@ -153,6 +153,7 @@ COND_SYSCALL_COMPAT(get_robust_list); + /* kernel/futex2.c */ + COND_SYSCALL(futex_wait); + COND_SYSCALL(futex_wake); ++COND_SYSCALL(futex_waitv); + + /* kernel/hrtimer.c */ + +diff --git a/tools/include/uapi/asm-generic/unistd.h b/tools/include/uapi/asm-generic/unistd.h +index 738315f148fa..b1ab5e14d0c3 100644 +--- a/tools/include/uapi/asm-generic/unistd.h ++++ b/tools/include/uapi/asm-generic/unistd.h +@@ -870,8 +870,11 @@ __SYSCALL(__NR_futex_wait, sys_futex_wait) + #define __NR_futex_wake 444 + __SYSCALL(__NR_futex_wake, sys_futex_wake) + ++#define __NR_epoll_pwait2 445 ++__SC_COMP(__NR_futex_waitv, sys_futex_waitv, compat_sys_futex_waitv) ++ + #undef __NR_syscalls +-#define __NR_syscalls 445 ++#define __NR_syscalls 446 + + /* + * 32 bit systems traditionally used different +diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl +index 15d2b89b6ad7..820c1e4b1aa9 100644 +--- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl ++++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl +@@ -365,6 +365,7 @@ + 441 common epoll_pwait2 sys_epoll_pwait2 + 442 common futex_wait sys_futex_wait + 443 common futex_wake sys_futex_wake ++444 common futex_waitv sys_futex_waitv + + # + # Due to a historical design error, certain syscalls are numbered differently +-- +GitLab + +From f22443c43d18f487392cb2a3d2a6557ff6081ce0 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:01 -0300 +Subject: [PATCH] futex2: Implement requeue operation +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Implement requeue interface similary to FUTEX_CMP_REQUEUE operation. +This is the syscall implemented by this patch: + +futex_requeue(struct futex_requeue *uaddr1, struct futex_requeue *uaddr2, + unsigned int nr_wake, unsigned int nr_requeue, + unsigned int cmpval, unsigned int flags) + +struct futex_requeue { + void *uaddr; + unsigned int flags; +}; + +If (uaddr1->uaddr == cmpval), wake at uaddr1->uaddr a nr_wake number of +waiters and then, remove a number of nr_requeue waiters at uaddr1->uaddr +and add them to uaddr2->uaddr list. Each uaddr has its own set of flags, +that must be defined at struct futex_requeue (such as size, shared, NUMA). +The flags argument of the syscall is there just for the sake of +extensibility, and right now it needs to be zero. + +Return the number of the woken futexes + the number of requeued ones on +success, error code otherwise. + +Signed-off-by: André Almeida +--- + +The original FUTEX_CMP_REQUEUE interfaces is such as follows: + +futex(*uaddr1, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, *uaddr2, cmpval); + +Given that when this interface was created they was only one type of +futex (as opposed to futex2, where there is shared, sizes, and NUMA), +there was no way to specify individual flags for uaddr1 and 2. When +FUTEX_PRIVATE was implemented, a new opcode was created as well +(FUTEX_CMP_REQUEUE_PRIVATE), but they apply both futexes, so they +should be of the same type regarding private/shared. This imposes a +limitation on the use cases of the operation, and to overcome that at futex2, +`struct futex_requeue` was created, so one can set individual flags for +each futex. This flexibility is a trade-off with performance, given that +now we need to perform two extra copy_from_user(). One alternative would +be to use the upper half of flags bits to the first one, and the bottom +half for the second futex, but this would also impose limitations, given +that we would limit by half the flags possibilities. If equal futexes +are common enough, the following extension could be added to overcome +the current performance: + +- A flag FUTEX_REQUEUE_EQUAL is added to futex2() flags; +- If futex_requeue() see this flag, that means that both futexes uses + the same set of attributes. +- Then, the function parses the flags as of futex_wait/wake(). +- *uaddr1 and *uaddr2 are used as void* (instead of struct + futex_requeue) just like wait/wake(). + +In that way, we could avoid the copy_from_user(). +--- + arch/arm/tools/syscall.tbl | 1 + + arch/arm64/include/asm/unistd.h | 2 +- + arch/x86/entry/syscalls/syscall_32.tbl | 1 + + arch/x86/entry/syscalls/syscall_64.tbl | 1 + + include/linux/compat.h | 12 ++ + include/linux/syscalls.h | 5 + + include/uapi/asm-generic/unistd.h | 5 +- + include/uapi/linux/futex.h | 10 ++ + kernel/futex2.c | 215 +++++++++++++++++++++++++ + kernel/sys_ni.c | 1 + + 10 files changed, 251 insertions(+), 2 deletions(-) + +diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl +index f9b55f2ea444..24a700535747 100644 +--- a/arch/arm/tools/syscall.tbl ++++ b/arch/arm/tools/syscall.tbl +@@ -459,3 +459,4 @@ + 443 common futex_wait sys_futex_wait + 444 common futex_wake sys_futex_wake + 445 common futex_waitv sys_futex_waitv ++446 common futex_requeue sys_futex_requeue +diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h +index 64ebdc1ec581..d1cc2849dc00 100644 +--- a/arch/arm64/include/asm/unistd.h ++++ b/arch/arm64/include/asm/unistd.h +@@ -38,7 +38,7 @@ + #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) + #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) + +-#define __NR_compat_syscalls 445 ++#define __NR_compat_syscalls 446 + #endif + + #define __ARCH_WANT_SYS_CLONE +diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl +index 4bc546c841b0..4d0111f44d79 100644 +--- a/arch/x86/entry/syscalls/syscall_32.tbl ++++ b/arch/x86/entry/syscalls/syscall_32.tbl +@@ -450,3 +450,4 @@ + 443 i386 futex_wait sys_futex_wait + 444 i386 futex_wake sys_futex_wake + 445 i386 futex_waitv sys_futex_waitv compat_sys_futex_waitv ++446 i386 futex_requeue sys_futex_requeue compat_sys_futex_requeue +diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl +index a715e88e3d6d..61c0b47365e3 100644 +--- a/arch/x86/entry/syscalls/syscall_64.tbl ++++ b/arch/x86/entry/syscalls/syscall_64.tbl +@@ -367,6 +367,7 @@ + 443 common futex_wait sys_futex_wait + 444 common futex_wake sys_futex_wake + 445 common futex_waitv sys_futex_waitv ++446 common futex_requeue sys_futex_requeue + + # + # Due to a historical design error, certain syscalls are numbered differently +diff --git a/include/linux/compat.h b/include/linux/compat.h +index 041d18174350..d4c1b402b962 100644 +--- a/include/linux/compat.h ++++ b/include/linux/compat.h +@@ -371,6 +371,11 @@ struct compat_futex_waitv { + compat_uint_t flags; + }; + ++struct compat_futex_requeue { ++ compat_uptr_t uaddr; ++ compat_uint_t flags; ++}; ++ + #ifdef CONFIG_COMPAT_OLD_SIGACTION + struct compat_old_sigaction { + compat_uptr_t sa_handler; +@@ -665,6 +670,13 @@ asmlinkage long compat_sys_futex_waitv(struct compat_futex_waitv *waiters, + compat_uint_t nr_futexes, compat_uint_t flags, + struct __kernel_timespec __user *timo); + ++asmlinkage long compat_sys_futex_requeue(struct compat_futex_requeue *uaddr1, ++ struct compat_futex_requeue *uaddr2, ++ compat_uint_t nr_wake, ++ compat_uint_t nr_requeue, ++ compat_uint_t cmpval, ++ compat_uint_t flags); ++ + /* kernel/itimer.c */ + asmlinkage long compat_sys_getitimer(int which, + struct old_itimerval32 __user *it); +diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h +index 48e96fe7d8f6..b0675f236066 100644 +--- a/include/linux/syscalls.h ++++ b/include/linux/syscalls.h +@@ -70,6 +70,7 @@ struct clone_args; + struct open_how; + struct mount_attr; + struct futex_waitv; ++struct futex_requeue; + + #include + #include +@@ -629,6 +630,10 @@ asmlinkage long sys_futex_wake(void __user *uaddr, unsigned int nr_wake, + asmlinkage long sys_futex_waitv(struct futex_waitv __user *waiters, + unsigned int nr_futexes, unsigned int flags, + struct __kernel_timespec __user *timo); ++asmlinkage long sys_futex_requeue(struct futex_requeue __user *uaddr1, ++ struct futex_requeue __user *uaddr2, ++ unsigned int nr_wake, unsigned int nr_requeue, ++ unsigned int cmpval, unsigned int flags); + + /* kernel/hrtimer.c */ + asmlinkage long sys_nanosleep(struct __kernel_timespec __user *rqtp, +diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h +index 2a6adca37fe9..2778da551846 100644 +--- a/include/uapi/asm-generic/unistd.h ++++ b/include/uapi/asm-generic/unistd.h +@@ -873,8 +873,11 @@ __SYSCALL(__NR_futex_wake, sys_futex_wake) + #define __NR_futex_waitv 445 + __SC_COMP(__NR_futex_waitv, sys_futex_waitv, compat_sys_futex_waitv) + ++#define __NR_futex_requeue 446 ++__SC_COMP(__NR_futex_requeue, sys_futex_requeue, compat_sys_futex_requeue) ++ + #undef __NR_syscalls +-#define __NR_syscalls 446 ++#define __NR_syscalls 447 + + /* + * 32 bit systems traditionally used different +diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h +index 3216aee015d2..c15bfddcf1e2 100644 +--- a/include/uapi/linux/futex.h ++++ b/include/uapi/linux/futex.h +@@ -62,6 +62,16 @@ struct futex_waitv { + unsigned int flags; + }; + ++/** ++ * struct futex_requeue - Define an address and its flags for requeue operation ++ * @uaddr: User address of one of the requeue arguments ++ * @flags: Flags for this address ++ */ ++struct futex_requeue { ++ void __user *uaddr; ++ unsigned int flags; ++}; ++ + /* + * Support for robust futexes: the kernel cleans up held futexes at + * thread exit time. +diff --git a/kernel/futex2.c b/kernel/futex2.c +index 3290e51695eb..75c961b309bb 100644 +--- a/kernel/futex2.c ++++ b/kernel/futex2.c +@@ -975,6 +975,221 @@ SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, + return ret; + } + ++static void futex_double_unlock(struct futex_bucket *b1, struct futex_bucket *b2) ++{ ++ spin_unlock(&b1->lock); ++ if (b1 != b2) ++ spin_unlock(&b2->lock); ++} ++ ++static inline int __futex_requeue(struct futex_requeue rq1, ++ struct futex_requeue rq2, unsigned int nr_wake, ++ unsigned int nr_requeue, unsigned int cmpval, ++ bool shared1, bool shared2) ++{ ++ struct futex_waiter w1, w2, *aux, *tmp; ++ bool retry = false; ++ struct futex_bucket *b1, *b2; ++ DEFINE_WAKE_Q(wake_q); ++ u32 uval; ++ int ret; ++ ++ b1 = futex_get_bucket(rq1.uaddr, &w1.key, shared1); ++ if (IS_ERR(b1)) ++ return PTR_ERR(b1); ++ ++ b2 = futex_get_bucket(rq2.uaddr, &w2.key, shared2); ++ if (IS_ERR(b2)) ++ return PTR_ERR(b2); ++ ++retry: ++ if (shared1 && retry) { ++ b1 = futex_get_bucket(rq1.uaddr, &w1.key, shared1); ++ if (IS_ERR(b1)) ++ return PTR_ERR(b1); ++ } ++ ++ if (shared2 && retry) { ++ b2 = futex_get_bucket(rq2.uaddr, &w2.key, shared2); ++ if (IS_ERR(b2)) ++ return PTR_ERR(b2); ++ } ++ ++ bucket_inc_waiters(b2); ++ /* ++ * To ensure the locks are taken in the same order for all threads (and ++ * thus avoiding deadlocks), take the "smaller" one first ++ */ ++ if (b1 <= b2) { ++ spin_lock(&b1->lock); ++ if (b1 < b2) ++ spin_lock_nested(&b2->lock, SINGLE_DEPTH_NESTING); ++ } else { ++ spin_lock(&b2->lock); ++ spin_lock_nested(&b1->lock, SINGLE_DEPTH_NESTING); ++ } ++ ++ ret = futex_get_user(&uval, rq1.uaddr); ++ ++ if (unlikely(ret)) { ++ futex_double_unlock(b1, b2); ++ if (__get_user(uval, (u32 __user *)rq1.uaddr)) ++ return -EFAULT; ++ ++ bucket_dec_waiters(b2); ++ retry = true; ++ goto retry; ++ } ++ ++ if (uval != cmpval) { ++ futex_double_unlock(b1, b2); ++ ++ bucket_dec_waiters(b2); ++ return -EAGAIN; ++ } ++ ++ list_for_each_entry_safe(aux, tmp, &b1->list, list) { ++ if (futex_match(w1.key, aux->key)) { ++ if (ret < nr_wake) { ++ futex_mark_wake(aux, b1, &wake_q); ++ ret++; ++ continue; ++ } ++ ++ if (ret >= nr_wake + nr_requeue) ++ break; ++ ++ aux->key.pointer = w2.key.pointer; ++ aux->key.index = w2.key.index; ++ aux->key.offset = w2.key.offset; ++ ++ if (b1 != b2) { ++ list_del_init_careful(&aux->list); ++ bucket_dec_waiters(b1); ++ ++ list_add_tail(&aux->list, &b2->list); ++ bucket_inc_waiters(b2); ++ } ++ ret++; ++ } ++ } ++ ++ futex_double_unlock(b1, b2); ++ wake_up_q(&wake_q); ++ bucket_dec_waiters(b2); ++ ++ return ret; ++} ++ ++#ifdef CONFIG_COMPAT ++static int compat_futex_parse_requeue(struct futex_requeue *rq, ++ struct compat_futex_requeue __user *uaddr, ++ bool *shared) ++{ ++ struct compat_futex_requeue tmp; ++ ++ if (copy_from_user(&tmp, uaddr, sizeof(tmp))) ++ return -EFAULT; ++ ++ if (tmp.flags & ~FUTEXV_WAITER_MASK || ++ (tmp.flags & FUTEX_SIZE_MASK) != FUTEX_32) ++ return -EINVAL; ++ ++ *shared = (tmp.flags & FUTEX_SHARED_FLAG) ? true : false; ++ ++ rq->uaddr = compat_ptr(tmp.uaddr); ++ rq->flags = tmp.flags; ++ ++ return 0; ++} ++ ++COMPAT_SYSCALL_DEFINE6(futex_requeue, struct compat_futex_requeue __user *, uaddr1, ++ struct compat_futex_requeue __user *, uaddr2, ++ unsigned int, nr_wake, unsigned int, nr_requeue, ++ unsigned int, cmpval, unsigned int, flags) ++{ ++ struct futex_requeue rq1, rq2; ++ bool shared1, shared2; ++ int ret; ++ ++ if (flags) ++ return -EINVAL; ++ ++ ret = compat_futex_parse_requeue(&rq1, uaddr1, &shared1); ++ if (ret) ++ return ret; ++ ++ ret = compat_futex_parse_requeue(&rq2, uaddr2, &shared2); ++ if (ret) ++ return ret; ++ ++ return __futex_requeue(rq1, rq2, nr_wake, nr_requeue, cmpval, shared1, shared2); ++} ++#endif ++ ++/** ++ * futex_parse_requeue - Copy a user struct futex_requeue and check it's flags ++ * @rq: Kernel struct ++ * @uaddr: Address of user struct ++ * @shared: Out parameter, defines if this is a shared futex ++ * ++ * Return: 0 on success, error code otherwise ++ */ ++static int futex_parse_requeue(struct futex_requeue *rq, ++ struct futex_requeue __user *uaddr, bool *shared) ++{ ++ if (copy_from_user(rq, uaddr, sizeof(*rq))) ++ return -EFAULT; ++ ++ if (rq->flags & ~FUTEXV_WAITER_MASK || ++ (rq->flags & FUTEX_SIZE_MASK) != FUTEX_32) ++ return -EINVAL; ++ ++ *shared = (rq->flags & FUTEX_SHARED_FLAG) ? true : false; ++ ++ return 0; ++} ++ ++/** ++ * sys_futex_requeue - Wake futexes at uaddr1 and requeue from uaddr1 to uaddr2 ++ * @uaddr1: Address of futexes to be waken/dequeued ++ * @uaddr2: Address for the futexes to be enqueued ++ * @nr_wake: Number of futexes waiting in uaddr1 to be woken up ++ * @nr_requeue: Number of futexes to be requeued from uaddr1 to uaddr2 ++ * @cmpval: Expected value at uaddr1 ++ * @flags: Reserved flags arg for requeue operation expansion. Must be 0. ++ * ++ * If (uaddr1->uaddr == cmpval), wake at uaddr1->uaddr a nr_wake number of ++ * waiters and then, remove a number of nr_requeue waiters at uaddr1->uaddr ++ * and add then to uaddr2->uaddr list. Each uaddr has its own set of flags, ++ * that must be defined at struct futex_requeue (such as size, shared, NUMA). ++ * ++ * Return the number of the woken futexes + the number of requeued ones on ++ * success, error code otherwise. ++ */ ++SYSCALL_DEFINE6(futex_requeue, struct futex_requeue __user *, uaddr1, ++ struct futex_requeue __user *, uaddr2, ++ unsigned int, nr_wake, unsigned int, nr_requeue, ++ unsigned int, cmpval, unsigned int, flags) ++{ ++ struct futex_requeue rq1, rq2; ++ bool shared1, shared2; ++ int ret; ++ ++ if (flags) ++ return -EINVAL; ++ ++ ret = futex_parse_requeue(&rq1, uaddr1, &shared1); ++ if (ret) ++ return ret; ++ ++ ret = futex_parse_requeue(&rq2, uaddr2, &shared2); ++ if (ret) ++ return ret; ++ ++ return __futex_requeue(rq1, rq2, nr_wake, nr_requeue, cmpval, shared1, shared2); ++} ++ + static int __init futex2_init(void) + { + int i; +diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c +index 977890c58ab5..1750dfc416d8 100644 +--- a/kernel/sys_ni.c ++++ b/kernel/sys_ni.c +@@ -154,6 +154,7 @@ COND_SYSCALL_COMPAT(get_robust_list); + COND_SYSCALL(futex_wait); + COND_SYSCALL(futex_wake); + COND_SYSCALL(futex_waitv); ++COND_SYSCALL(futex_requeue); + + /* kernel/hrtimer.c */ + +-- +GitLab + +From a439256740d175a9a5f9da6f81af1ad070541151 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Thu, 11 Feb 2021 10:47:23 -0300 +Subject: [PATCH] futex2: Add compatibility entry point for x86_x32 ABI +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +New syscalls should use the same entry point for x86_64 and x86_x32 +paths. Add a wrapper for x32 calls to use parse functions that assumes +32bit pointers. + +Signed-off-by: André Almeida +--- + kernel/futex2.c | 42 +++++++++++++++++++++++++++++++++++------- + 1 file changed, 35 insertions(+), 7 deletions(-) + +diff --git a/kernel/futex2.c b/kernel/futex2.c +index 75c961b309bb..61b81b401e58 100644 +--- a/kernel/futex2.c ++++ b/kernel/futex2.c +@@ -23,6 +23,10 @@ + #include + #include + ++#ifdef CONFIG_X86_64 ++#include ++#endif ++ + /** + * struct futex_key - Components to build unique key for a futex + * @pointer: Pointer to current->mm or inode's UUID for file backed futexes +@@ -872,7 +876,16 @@ SYSCALL_DEFINE4(futex_waitv, struct futex_waitv __user *, waiters, + futexv->hint = false; + futexv->task = current; + +- ret = futex_parse_waitv(futexv, waiters, nr_futexes); ++#ifdef CONFIG_X86_X32_ABI ++ if (in_x32_syscall()) { ++ ret = compat_futex_parse_waitv(futexv, (struct compat_futex_waitv *)waiters, ++ nr_futexes); ++ } else ++#endif ++ { ++ ret = futex_parse_waitv(futexv, waiters, nr_futexes); ++ } ++ + if (!ret) + ret = futex_set_timer_and_wait(futexv, nr_futexes, timo, flags); + +@@ -1179,13 +1192,28 @@ SYSCALL_DEFINE6(futex_requeue, struct futex_requeue __user *, uaddr1, + if (flags) + return -EINVAL; + +- ret = futex_parse_requeue(&rq1, uaddr1, &shared1); +- if (ret) +- return ret; ++#ifdef CONFIG_X86_X32_ABI ++ if (in_x32_syscall()) { ++ ret = compat_futex_parse_requeue(&rq1, (struct compat_futex_requeue *)uaddr1, ++ &shared1); ++ if (ret) ++ return ret; + +- ret = futex_parse_requeue(&rq2, uaddr2, &shared2); +- if (ret) +- return ret; ++ ret = compat_futex_parse_requeue(&rq2, (struct compat_futex_requeue *)uaddr2, ++ &shared2); ++ if (ret) ++ return ret; ++ } else ++#endif ++ { ++ ret = futex_parse_requeue(&rq1, uaddr1, &shared1); ++ if (ret) ++ return ret; ++ ++ ret = futex_parse_requeue(&rq2, uaddr2, &shared2); ++ if (ret) ++ return ret; ++ } + + return __futex_requeue(rq1, rq2, nr_wake, nr_requeue, cmpval, shared1, shared2); + } +-- +GitLab + +From 6ae4534eedef59fa3bd48e4cc03961813e10f643 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Tue, 9 Feb 2021 13:59:00 -0300 +Subject: [PATCH] docs: locking: futex2: Add documentation +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Add a new documentation file specifying both userspace API and internal +implementation details of futex2 syscalls. + +Signed-off-by: André Almeida +--- + Documentation/locking/futex2.rst | 198 +++++++++++++++++++++++++++++++ + Documentation/locking/index.rst | 1 + + 2 files changed, 199 insertions(+) + create mode 100644 Documentation/locking/futex2.rst + +diff --git a/Documentation/locking/futex2.rst b/Documentation/locking/futex2.rst +new file mode 100644 +index 000000000000..3ab49f0e741c +--- /dev/null ++++ b/Documentation/locking/futex2.rst +@@ -0,0 +1,198 @@ ++.. SPDX-License-Identifier: GPL-2.0 ++ ++====== ++futex2 ++====== ++ ++:Author: André Almeida ++ ++futex, or fast user mutex, is a set of syscalls to allow userspace to create ++performant synchronization mechanisms, such as mutexes, semaphores and ++conditional variables in userspace. C standard libraries, like glibc, uses it ++as a means to implement more high level interfaces like pthreads. ++ ++The interface ++============= ++ ++uAPI functions ++-------------- ++ ++.. kernel-doc:: kernel/futex2.c ++ :identifiers: sys_futex_wait sys_futex_wake sys_futex_waitv sys_futex_requeue ++ ++uAPI structures ++--------------- ++ ++.. kernel-doc:: include/uapi/linux/futex.h ++ ++The ``flag`` argument ++--------------------- ++ ++The flag is used to specify the size of the futex word ++(FUTEX_[8, 16, 32]). It's mandatory to define one, since there's no ++default size. ++ ++By default, the timeout uses a monotonic clock, but can be used as a realtime ++one by using the FUTEX_REALTIME_CLOCK flag. ++ ++By default, futexes are of the private type, that means that this user address ++will be accessed by threads that share the same memory region. This allows for ++some internal optimizations, so they are faster. However, if the address needs ++to be shared with different processes (like using ``mmap()`` or ``shm()``), they ++need to be defined as shared and the flag FUTEX_SHARED_FLAG is used to set that. ++ ++By default, the operation has no NUMA-awareness, meaning that the user can't ++choose the memory node where the kernel side futex data will be stored. The ++user can choose the node where it wants to operate by setting the ++FUTEX_NUMA_FLAG and using the following structure (where X can be 8, 16, or ++32):: ++ ++ struct futexX_numa { ++ __uX value; ++ __sX hint; ++ }; ++ ++This structure should be passed at the ``void *uaddr`` of futex functions. The ++address of the structure will be used to be waited on/waken on, and the ++``value`` will be compared to ``val`` as usual. The ``hint`` member is used to ++define which node the futex will use. When waiting, the futex will be ++registered on a kernel-side table stored on that node; when waking, the futex ++will be searched for on that given table. That means that there's no redundancy ++between tables, and the wrong ``hint`` value will lead to undesired behavior. ++Userspace is responsible for dealing with node migrations issues that may ++occur. ``hint`` can range from [0, MAX_NUMA_NODES), for specifying a node, or ++-1, to use the same node the current process is using. ++ ++When not using FUTEX_NUMA_FLAG on a NUMA system, the futex will be stored on a ++global table on allocated on the first node. ++ ++The ``timo`` argument ++--------------------- ++ ++As per the Y2038 work done in the kernel, new interfaces shouldn't add timeout ++options known to be buggy. Given that, ``timo`` should be a 64-bit timeout at ++all platforms, using an absolute timeout value. ++ ++Implementation ++============== ++ ++The internal implementation follows a similar design to the original futex. ++Given that we want to replicate the same external behavior of current futex, ++this should be somewhat expected. ++ ++Waiting ++------- ++ ++For the wait operations, they are all treated as if you want to wait on N ++futexes, so the path for futex_wait and futex_waitv is the basically the same. ++For both syscalls, the first step is to prepare an internal list for the list ++of futexes to wait for (using struct futexv_head). For futex_wait() calls, this ++list will have a single object. ++ ++We have a hash table, where waiters register themselves before sleeping. Then ++the wake function checks this table looking for waiters at uaddr. The hash ++bucket to be used is determined by a struct futex_key, that stores information ++to uniquely identify an address from a given process. Given the huge address ++space, there'll be hash collisions, so we store information to be later used on ++collision treatment. ++ ++First, for every futex we want to wait on, we check if (``*uaddr == val``). ++This check is done holding the bucket lock, so we are correctly serialized with ++any futex_wake() calls. If any waiter fails the check above, we dequeue all ++futexes. The check (``*uaddr == val``) can fail for two reasons: ++ ++- The values are different, and we return -EAGAIN. However, if while ++ dequeueing we found that some futexes were awakened, we prioritize this ++ and return success. ++ ++- When trying to access the user address, we do so with page faults ++ disabled because we are holding a bucket's spin lock (and can't sleep ++ while holding a spin lock). If there's an error, it might be a page ++ fault, or an invalid address. We release the lock, dequeue everyone ++ (because it's illegal to sleep while there are futexes enqueued, we ++ could lose wakeups) and try again with page fault enabled. If we ++ succeed, this means that the address is valid, but we need to do ++ all the work again. For serialization reasons, we need to have the ++ spin lock when getting the user value. Additionally, for shared ++ futexes, we also need to recalculate the hash, since the underlying ++ mapping mechanisms could have changed when dealing with page fault. ++ If, even with page fault enabled, we can't access the address, it ++ means it's an invalid user address, and we return -EFAULT. For this ++ case, we prioritize the error, even if some futexes were awaken. ++ ++If the check is OK, they are enqueued on a linked list in our bucket, and ++proceed to the next one. If all waiters succeed, we put the thread to sleep ++until a futex_wake() call, timeout expires or we get a signal. After waking up, ++we dequeue everyone, and check if some futex was awakened. This dequeue is done ++by iteratively walking at each element of struct futex_head list. ++ ++All enqueuing/dequeuing operations requires to hold the bucket lock, to avoid ++racing while modifying the list. ++ ++Waking ++------ ++ ++We get the bucket that's storing the waiters at uaddr, and wake the required ++number of waiters, checking for hash collision. ++ ++There's an optimization that makes futex_wake() not take the bucket lock if ++there's no one to be woken on that bucket. It checks an atomic counter that each ++bucket has, if it says 0, then the syscall exits. In order for this to work, the ++waiter thread increases it before taking the lock, so the wake thread will ++correctly see that there's someone waiting and will continue the path to take ++the bucket lock. To get the correct serialization, the waiter issues a memory ++barrier after increasing the bucket counter and the waker issues a memory ++barrier before checking it. ++ ++Requeuing ++--------- ++ ++The requeue path first checks for each struct futex_requeue and their flags. ++Then, it will compare the expected value with the one at uaddr1::uaddr. ++Following the same serialization explained at Waking_, we increase the atomic ++counter for the bucket of uaddr2 before taking the lock. We need to have both ++buckets locks at same time so we don't race with other futex operation. To ++ensure the locks are taken in the same order for all threads (and thus avoiding ++deadlocks), every requeue operation takes the "smaller" bucket first, when ++comparing both addresses. ++ ++If the compare with user value succeeds, we proceed by waking ``nr_wake`` ++futexes, and then requeuing ``nr_requeue`` from bucket of uaddr1 to the uaddr2. ++This consists in a simple list deletion/addition and replacing the old futex key ++with the new one. ++ ++Futex keys ++---------- ++ ++There are two types of futexes: private and shared ones. The private are futexes ++meant to be used by threads that share the same memory space, are easier to be ++uniquely identified and thus can have some performance optimization. The ++elements for identifying one are: the start address of the page where the ++address is, the address offset within the page and the current->mm pointer. ++ ++Now, for uniquely identifying a shared futex: ++ ++- If the page containing the user address is an anonymous page, we can ++ just use the same data used for private futexes (the start address of ++ the page, the address offset within the page and the current->mm ++ pointer); that will be enough for uniquely identifying such futex. We ++ also set one bit at the key to differentiate if a private futex is ++ used on the same address (mixing shared and private calls does not ++ work). ++ ++- If the page is file-backed, current->mm maybe isn't the same one for ++ every user of this futex, so we need to use other data: the ++ page->index, a UUID for the struct inode and the offset within the ++ page. ++ ++Note that members of futex_key don't have any particular meaning after they ++are part of the struct - they are just bytes to identify a futex. Given that, ++we don't need to use a particular name or type that matches the original data, ++we only need to care about the bitsize of each component and make both private ++and shared fit in the same memory space. ++ ++Source code documentation ++========================= ++ ++.. kernel-doc:: kernel/futex2.c ++ :no-identifiers: sys_futex_wait sys_futex_wake sys_futex_waitv sys_futex_requeue +diff --git a/Documentation/locking/index.rst b/Documentation/locking/index.rst +index 7003bd5aeff4..9bf03c7fa1ec 100644 +--- a/Documentation/locking/index.rst ++++ b/Documentation/locking/index.rst +@@ -24,6 +24,7 @@ locking + percpu-rw-semaphore + robust-futexes + robust-futex-ABI ++ futex2 + + .. only:: subproject and html + +-- +GitLab + +From 2e88815c729ee716e3ce15c0b182d9a0d7958079 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:01 -0300 +Subject: [PATCH] selftests: futex2: Add wake/wait test +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Add a simple file to test wake/wait mechanism using futex2 interface. +Test three scenarios: using a common local int variable as private +futex, a shm futex as shared futex and a file-backed shared memory as a +shared futex. This should test all branches of futex_get_key(). + +Create helper files so more tests can evaluate futex2. While 32bit ABIs +from glibc aren't yet able to use 64 bit sized time variables, add a +temporary workaround that implements the required types and calls the +appropriated syscalls, since futex2 doesn't supports 32 bit sized time. + +Signed-off-by: André Almeida +--- + .../selftests/futex/functional/.gitignore | 1 + + .../selftests/futex/functional/Makefile | 6 +- + .../selftests/futex/functional/futex2_wait.c | 209 ++++++++++++++++++ + .../testing/selftests/futex/functional/run.sh | 3 + + .../selftests/futex/include/futex2test.h | 79 +++++++ + 5 files changed, 296 insertions(+), 2 deletions(-) + create mode 100644 tools/testing/selftests/futex/functional/futex2_wait.c + create mode 100644 tools/testing/selftests/futex/include/futex2test.h + +diff --git a/tools/testing/selftests/futex/functional/.gitignore b/tools/testing/selftests/futex/functional/.gitignore +index 0efcd494daab..d61f1df94360 100644 +--- a/tools/testing/selftests/futex/functional/.gitignore ++++ b/tools/testing/selftests/futex/functional/.gitignore +@@ -6,3 +6,4 @@ futex_wait_private_mapped_file + futex_wait_timeout + futex_wait_uninitialized_heap + futex_wait_wouldblock ++futex2_wait +diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile +index 23207829ec75..9b334f190759 100644 +--- a/tools/testing/selftests/futex/functional/Makefile ++++ b/tools/testing/selftests/futex/functional/Makefile +@@ -1,10 +1,11 @@ + # SPDX-License-Identifier: GPL-2.0 +-INCLUDES := -I../include -I../../ ++INCLUDES := -I../include -I../../ -I../../../../../usr/include/ + CFLAGS := $(CFLAGS) -g -O2 -Wall -D_GNU_SOURCE -pthread $(INCLUDES) + LDLIBS := -lpthread -lrt + + HEADERS := \ + ../include/futextest.h \ ++ ../include/futex2test.h \ + ../include/atomic.h \ + ../include/logging.h + TEST_GEN_FILES := \ +@@ -14,7 +15,8 @@ TEST_GEN_FILES := \ + futex_requeue_pi_signal_restart \ + futex_requeue_pi_mismatched_ops \ + futex_wait_uninitialized_heap \ +- futex_wait_private_mapped_file ++ futex_wait_private_mapped_file \ ++ futex2_wait + + TEST_PROGS := run.sh + +diff --git a/tools/testing/selftests/futex/functional/futex2_wait.c b/tools/testing/selftests/futex/functional/futex2_wait.c +new file mode 100644 +index 000000000000..4b5416585c79 +--- /dev/null ++++ b/tools/testing/selftests/futex/functional/futex2_wait.c +@@ -0,0 +1,209 @@ ++// SPDX-License-Identifier: GPL-2.0-or-later ++/****************************************************************************** ++ * ++ * Copyright Collabora Ltd., 2021 ++ * ++ * DESCRIPTION ++ * Test wait/wake mechanism of futex2, using 32bit sized futexes. ++ * ++ * AUTHOR ++ * André Almeida ++ * ++ * HISTORY ++ * 2021-Feb-5: Initial version by André ++ * ++ *****************************************************************************/ ++ ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include "futex2test.h" ++#include "logging.h" ++ ++#define TEST_NAME "futex2-wait" ++#define timeout_ns 30000000 ++#define WAKE_WAIT_US 10000 ++#define SHM_PATH "futex2_shm_file" ++futex_t *f1; ++ ++void usage(char *prog) ++{ ++ printf("Usage: %s\n", prog); ++ printf(" -c Use color\n"); ++ printf(" -h Display this help message\n"); ++ printf(" -v L Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n", ++ VQUIET, VCRITICAL, VINFO); ++} ++ ++void *waiterfn(void *arg) ++{ ++ struct timespec64 to64; ++ unsigned int flags = 0; ++ ++ if (arg) ++ flags = *((unsigned int *) arg); ++ ++ /* setting absolute timeout for futex2 */ ++ if (gettime64(CLOCK_MONOTONIC, &to64)) ++ error("gettime64 failed\n", errno); ++ ++ to64.tv_nsec += timeout_ns; ++ ++ if (to64.tv_nsec >= 1000000000) { ++ to64.tv_sec++; ++ to64.tv_nsec -= 1000000000; ++ } ++ ++ if (futex2_wait(f1, *f1, FUTEX_32 | flags, &to64)) ++ printf("waiter failed errno %d\n", errno); ++ ++ return NULL; ++} ++ ++void *waitershm(void *arg) ++{ ++ futex2_wait(arg, 0, FUTEX_32 | FUTEX_SHARED_FLAG, NULL); ++ ++ return NULL; ++} ++ ++int main(int argc, char *argv[]) ++{ ++ pthread_t waiter; ++ unsigned int flags = FUTEX_SHARED_FLAG; ++ int res, ret = RET_PASS; ++ int c; ++ futex_t f_private = 0; ++ ++ f1 = &f_private; ++ ++ while ((c = getopt(argc, argv, "cht:v:")) != -1) { ++ switch (c) { ++ case 'c': ++ log_color(1); ++ break; ++ case 'h': ++ usage(basename(argv[0])); ++ exit(0); ++ case 'v': ++ log_verbosity(atoi(optarg)); ++ break; ++ default: ++ usage(basename(argv[0])); ++ exit(1); ++ } ++ } ++ ++ ksft_print_header(); ++ ksft_set_plan(3); ++ ksft_print_msg("%s: Test FUTEX2_WAIT\n", ++ basename(argv[0])); ++ ++ /* Testing a private futex */ ++ info("Calling private futex2_wait on f1: %u @ %p with val=%u\n", *f1, f1, *f1); ++ ++ if (pthread_create(&waiter, NULL, waiterfn, NULL)) ++ error("pthread_create failed\n", errno); ++ ++ usleep(WAKE_WAIT_US); ++ ++ info("Calling private futex2_wake on f1: %u @ %p with val=%u\n", *f1, f1, *f1); ++ res = futex2_wake(f1, 1, FUTEX_32); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_wake private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_wake private succeeds\n"); ++ } ++ ++ int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); ++ ++ if (shm_id < 0) { ++ perror("shmget"); ++ exit(1); ++ } ++ ++ /* Testing an anon page shared memory */ ++ unsigned int *shared_data = shmat(shm_id, NULL, 0); ++ ++ *shared_data = 0; ++ f1 = shared_data; ++ ++ info("Calling shared futex2_wait on f1: %u @ %p with val=%u\n", *f1, f1, *f1); ++ ++ if (pthread_create(&waiter, NULL, waiterfn, &flags)) ++ error("pthread_create failed\n", errno); ++ ++ usleep(WAKE_WAIT_US); ++ ++ info("Calling shared futex2_wake on f1: %u @ %p with val=%u\n", *f1, f1, *f1); ++ res = futex2_wake(f1, 1, FUTEX_32 | FUTEX_SHARED_FLAG); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_wake shared (shmget) returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_wake shared (shmget) succeeds\n"); ++ } ++ ++ shmdt(shared_data); ++ ++ /* Testing a file backed shared memory */ ++ void *shm; ++ int fd, pid; ++ ++ f_private = 0; ++ ++ fd = open(SHM_PATH, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR); ++ if (fd < 0) { ++ perror("open"); ++ exit(1); ++ } ++ ++ res = ftruncate(fd, sizeof(f_private)); ++ if (res) { ++ perror("ftruncate"); ++ exit(1); ++ } ++ ++ shm = mmap(NULL, sizeof(f_private), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); ++ if (shm == MAP_FAILED) { ++ perror("mmap"); ++ exit(1); ++ } ++ ++ memcpy(shm, &f_private, sizeof(f_private)); ++ ++ pthread_create(&waiter, NULL, waitershm, shm); ++ ++ usleep(WAKE_WAIT_US); ++ ++ res = futex2_wake(shm, 1, FUTEX_32 | FUTEX_SHARED_FLAG); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_wake shared (mmap) returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_wake shared (mmap) succeeds\n"); ++ } ++ ++ munmap(shm, sizeof(f_private)); ++ ++ remove(SHM_PATH); ++ ++ ksft_print_cnts(); ++ return ret; ++} +diff --git a/tools/testing/selftests/futex/functional/run.sh b/tools/testing/selftests/futex/functional/run.sh +index 1acb6ace1680..3730159c865a 100755 +--- a/tools/testing/selftests/futex/functional/run.sh ++++ b/tools/testing/selftests/futex/functional/run.sh +@@ -73,3 +73,6 @@ echo + echo + ./futex_wait_uninitialized_heap $COLOR + ./futex_wait_private_mapped_file $COLOR ++ ++echo ++./futex2_wait $COLOR +diff --git a/tools/testing/selftests/futex/include/futex2test.h b/tools/testing/selftests/futex/include/futex2test.h +new file mode 100644 +index 000000000000..e724d56b917e +--- /dev/null ++++ b/tools/testing/selftests/futex/include/futex2test.h +@@ -0,0 +1,79 @@ ++/* SPDX-License-Identifier: GPL-2.0-or-later */ ++/****************************************************************************** ++ * ++ * Copyright Collabora Ltd., 2021 ++ * ++ * DESCRIPTION ++ * Futex2 library addons for old futex library ++ * ++ * AUTHOR ++ * André Almeida ++ * ++ * HISTORY ++ * 2021-Feb-5: Initial version by André ++ * ++ *****************************************************************************/ ++#include "futextest.h" ++#include ++ ++#define NSEC_PER_SEC 1000000000L ++ ++#ifndef FUTEX_8 ++# define FUTEX_8 0 ++#endif ++#ifndef FUTEX_16 ++# define FUTEX_16 1 ++#endif ++#ifndef FUTEX_32 ++# define FUTEX_32 2 ++#endif ++ ++/* ++ * - Y2038 section for 32-bit applications - ++ * ++ * Remove this when glibc is ready for y2038. Then, always compile with ++ * `-DTIME_BITS=64` or `-D__USE_TIME_BITS64`. glibc will provide both ++ * timespec64 and clock_gettime64 so we won't need to define here. ++ */ ++#if defined(__i386__) || __TIMESIZE == 32 ++# define NR_gettime __NR_clock_gettime64 ++#else ++# define NR_gettime __NR_clock_gettime ++#endif ++ ++struct timespec64 { ++ long long tv_sec; /* seconds */ ++ long long tv_nsec; /* nanoseconds */ ++}; ++ ++int gettime64(clock_t clockid, struct timespec64 *tv) ++{ ++ return syscall(NR_gettime, clockid, tv); ++} ++/* ++ * - End of Y2038 section - ++ */ ++ ++/** ++ * futex2_wait - If (*uaddr == val), wait at uaddr until timo ++ * @uaddr: User address to wait on ++ * @val: Expected value at uaddr, return if is not equal ++ * @flags: Operation flags ++ * @timo: Optional timeout for operation ++ */ ++static inline int futex2_wait(volatile void *uaddr, unsigned long val, ++ unsigned long flags, struct timespec64 *timo) ++{ ++ return syscall(__NR_futex_wait, uaddr, val, flags, timo); ++} ++ ++/** ++ * futex2_wake - Wake a number of waiters at uaddr ++ * @uaddr: Address to wake ++ * @nr: Number of waiters to wake ++ * @flags: Operation flags ++ */ ++static inline int futex2_wake(volatile void *uaddr, unsigned int nr, unsigned long flags) ++{ ++ return syscall(__NR_futex_wake, uaddr, nr, flags); ++} +-- +GitLab + +From 4564c36175c0c0cf31cac0fd1e94c4813b6c7244 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:01 -0300 +Subject: [PATCH] selftests: futex2: Add timeout test +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Adapt existing futex wait timeout file to test the same mechanism for +futex2. futex2 accepts only absolute 64bit timers, but supports both +monotonic and realtime clocks. + +Signed-off-by: André Almeida +--- + .../futex/functional/futex_wait_timeout.c | 58 ++++++++++++++++--- + 1 file changed, 49 insertions(+), 9 deletions(-) + +diff --git a/tools/testing/selftests/futex/functional/futex_wait_timeout.c b/tools/testing/selftests/futex/functional/futex_wait_timeout.c +index ee55e6d389a3..b4dffe9e3b44 100644 +--- a/tools/testing/selftests/futex/functional/futex_wait_timeout.c ++++ b/tools/testing/selftests/futex/functional/futex_wait_timeout.c +@@ -11,6 +11,7 @@ + * + * HISTORY + * 2009-Nov-6: Initial version by Darren Hart ++ * 2021-Feb-5: Add futex2 test by André + * + *****************************************************************************/ + +@@ -20,7 +21,7 @@ + #include + #include + #include +-#include "futextest.h" ++#include "futex2test.h" + #include "logging.h" + + #define TEST_NAME "futex-wait-timeout" +@@ -40,7 +41,8 @@ void usage(char *prog) + int main(int argc, char *argv[]) + { + futex_t f1 = FUTEX_INITIALIZER; +- struct timespec to; ++ struct timespec to = {.tv_sec = 0, .tv_nsec = timeout_ns}; ++ struct timespec64 to64; + int res, ret = RET_PASS; + int c; + +@@ -65,22 +67,60 @@ int main(int argc, char *argv[]) + } + + ksft_print_header(); +- ksft_set_plan(1); ++ ksft_set_plan(3); + ksft_print_msg("%s: Block on a futex and wait for timeout\n", + basename(argv[0])); + ksft_print_msg("\tArguments: timeout=%ldns\n", timeout_ns); + +- /* initialize timeout */ +- to.tv_sec = 0; +- to.tv_nsec = timeout_ns; +- + info("Calling futex_wait on f1: %u @ %p\n", f1, &f1); + res = futex_wait(&f1, f1, &to, FUTEX_PRIVATE_FLAG); + if (!res || errno != ETIMEDOUT) { +- fail("futex_wait returned %d\n", ret < 0 ? errno : ret); ++ ksft_test_result_fail("futex_wait returned %d\n", ret < 0 ? errno : ret); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex_wait timeout succeeds\n"); ++ } ++ ++ /* setting absolute monotonic timeout for futex2 */ ++ if (gettime64(CLOCK_MONOTONIC, &to64)) ++ error("gettime64 failed\n", errno); ++ ++ to64.tv_nsec += timeout_ns; ++ ++ if (to64.tv_nsec >= 1000000000) { ++ to64.tv_sec++; ++ to64.tv_nsec -= 1000000000; ++ } ++ ++ info("Calling futex2_wait on f1: %u @ %p\n", f1, &f1); ++ res = futex2_wait(&f1, f1, FUTEX_32, &to64); ++ if (!res || errno != ETIMEDOUT) { ++ ksft_test_result_fail("futex2_wait monotonic returned %d\n", ret < 0 ? errno : ret); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_wait monotonic timeout succeeds\n"); ++ } ++ ++ /* setting absolute realtime timeout for futex2 */ ++ if (gettime64(CLOCK_REALTIME, &to64)) ++ error("gettime64 failed\n", errno); ++ ++ to64.tv_nsec += timeout_ns; ++ ++ if (to64.tv_nsec >= 1000000000) { ++ to64.tv_sec++; ++ to64.tv_nsec -= 1000000000; ++ } ++ ++ info("Calling futex2_wait on f1: %u @ %p\n", f1, &f1); ++ res = futex2_wait(&f1, f1, FUTEX_32 | FUTEX_CLOCK_REALTIME, &to64); ++ if (!res || errno != ETIMEDOUT) { ++ ksft_test_result_fail("futex2_wait realtime returned %d\n", ret < 0 ? errno : ret); + ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_wait realtime timeout succeeds\n"); + } + +- print_result(TEST_NAME, ret); ++ ksft_print_cnts(); + return ret; + } +-- +GitLab + +From 3e2b4ab146c93d51e083f410b34be3ccb2bbee5b Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:01 -0300 +Subject: [PATCH] selftests: futex2: Add wouldblock test +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Adapt existing futex wait wouldblock file to test the same mechanism for +futex2. + +Signed-off-by: André Almeida +--- + .../futex/functional/futex_wait_wouldblock.c | 33 ++++++++++++++++--- + 1 file changed, 29 insertions(+), 4 deletions(-) + +diff --git a/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c b/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c +index 0ae390ff8164..ed3660090907 100644 +--- a/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c ++++ b/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c +@@ -12,6 +12,7 @@ + * + * HISTORY + * 2009-Nov-14: Initial version by Gowrishankar ++ * 2021-Feb-5: Add futex2 test by André + * + *****************************************************************************/ + +@@ -21,7 +22,7 @@ + #include + #include + #include +-#include "futextest.h" ++#include "futex2test.h" + #include "logging.h" + + #define TEST_NAME "futex-wait-wouldblock" +@@ -39,6 +40,7 @@ void usage(char *prog) + int main(int argc, char *argv[]) + { + struct timespec to = {.tv_sec = 0, .tv_nsec = timeout_ns}; ++ struct timespec64 to64; + futex_t f1 = FUTEX_INITIALIZER; + int res, ret = RET_PASS; + int c; +@@ -61,18 +63,41 @@ int main(int argc, char *argv[]) + } + + ksft_print_header(); +- ksft_set_plan(1); ++ ksft_set_plan(2); + ksft_print_msg("%s: Test the unexpected futex value in FUTEX_WAIT\n", + basename(argv[0])); + + info("Calling futex_wait on f1: %u @ %p with val=%u\n", f1, &f1, f1+1); + res = futex_wait(&f1, f1+1, &to, FUTEX_PRIVATE_FLAG); + if (!res || errno != EWOULDBLOCK) { +- fail("futex_wait returned: %d %s\n", ++ ksft_test_result_fail("futex_wait returned: %d %s\n", + res ? errno : res, res ? strerror(errno) : ""); + ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex_wait wouldblock succeeds\n"); + } + +- print_result(TEST_NAME, ret); ++ /* setting absolute timeout for futex2 */ ++ if (gettime64(CLOCK_MONOTONIC, &to64)) ++ error("gettime64 failed\n", errno); ++ ++ to64.tv_nsec += timeout_ns; ++ ++ if (to64.tv_nsec >= 1000000000) { ++ to64.tv_sec++; ++ to64.tv_nsec -= 1000000000; ++ } ++ ++ info("Calling futex2_wait on f1: %u @ %p with val=%u\n", f1, &f1, f1+1); ++ res = futex2_wait(&f1, f1+1, FUTEX_32, &to64); ++ if (!res || errno != EWOULDBLOCK) { ++ ksft_test_result_fail("futex2_wait returned: %d %s\n", ++ res ? errno : res, res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_wait wouldblock succeeds\n"); ++ } ++ ++ ksft_print_cnts(); + return ret; + } +-- +GitLab + +From 671e79d935493cdc5aa05a7e3a96547adbb3c200 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:02 -0300 +Subject: [PATCH] selftests: futex2: Add waitv test +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Create a new file to test the waitv mechanism. Test both private and +shared futexes. Wake the last futex in the array, and check if the +return value from futex_waitv() is the right index. + +Signed-off-by: André Almeida +--- + .../selftests/futex/functional/.gitignore | 1 + + .../selftests/futex/functional/Makefile | 3 +- + .../selftests/futex/functional/futex2_waitv.c | 157 ++++++++++++++++++ + .../testing/selftests/futex/functional/run.sh | 3 + + .../selftests/futex/include/futex2test.h | 26 +++ + 5 files changed, 189 insertions(+), 1 deletion(-) + create mode 100644 tools/testing/selftests/futex/functional/futex2_waitv.c + +diff --git a/tools/testing/selftests/futex/functional/.gitignore b/tools/testing/selftests/futex/functional/.gitignore +index d61f1df94360..d0b8f637b786 100644 +--- a/tools/testing/selftests/futex/functional/.gitignore ++++ b/tools/testing/selftests/futex/functional/.gitignore +@@ -7,3 +7,4 @@ futex_wait_timeout + futex_wait_uninitialized_heap + futex_wait_wouldblock + futex2_wait ++futex2_waitv +diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile +index 9b334f190759..09c08ccdeaf2 100644 +--- a/tools/testing/selftests/futex/functional/Makefile ++++ b/tools/testing/selftests/futex/functional/Makefile +@@ -16,7 +16,8 @@ TEST_GEN_FILES := \ + futex_requeue_pi_mismatched_ops \ + futex_wait_uninitialized_heap \ + futex_wait_private_mapped_file \ +- futex2_wait ++ futex2_wait \ ++ futex2_waitv + + TEST_PROGS := run.sh + +diff --git a/tools/testing/selftests/futex/functional/futex2_waitv.c b/tools/testing/selftests/futex/functional/futex2_waitv.c +new file mode 100644 +index 000000000000..2f81d296d95d +--- /dev/null ++++ b/tools/testing/selftests/futex/functional/futex2_waitv.c +@@ -0,0 +1,157 @@ ++// SPDX-License-Identifier: GPL-2.0-or-later ++/****************************************************************************** ++ * ++ * Copyright Collabora Ltd., 2021 ++ * ++ * DESCRIPTION ++ * Test waitv/wake mechanism of futex2, using 32bit sized futexes. ++ * ++ * AUTHOR ++ * André Almeida ++ * ++ * HISTORY ++ * 2021-Feb-5: Initial version by André ++ * ++ *****************************************************************************/ ++ ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include "futex2test.h" ++#include "logging.h" ++ ++#define TEST_NAME "futex2-wait" ++#define timeout_ns 1000000000 ++#define WAKE_WAIT_US 10000 ++#define NR_FUTEXES 30 ++struct futex_waitv waitv[NR_FUTEXES]; ++u_int32_t futexes[NR_FUTEXES] = {0}; ++ ++void usage(char *prog) ++{ ++ printf("Usage: %s\n", prog); ++ printf(" -c Use color\n"); ++ printf(" -h Display this help message\n"); ++ printf(" -v L Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n", ++ VQUIET, VCRITICAL, VINFO); ++} ++ ++void *waiterfn(void *arg) ++{ ++ struct timespec64 to64; ++ int res; ++ ++ /* setting absolute timeout for futex2 */ ++ if (gettime64(CLOCK_MONOTONIC, &to64)) ++ error("gettime64 failed\n", errno); ++ ++ to64.tv_sec++; ++ ++ res = futex2_waitv(waitv, NR_FUTEXES, 0, &to64); ++ if (res < 0) { ++ ksft_test_result_fail("futex2_waitv private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ } else if (res != NR_FUTEXES - 1) { ++ ksft_test_result_fail("futex2_waitv private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ } ++ ++ return NULL; ++} ++ ++int main(int argc, char *argv[]) ++{ ++ pthread_t waiter; ++ int res, ret = RET_PASS; ++ int c, i; ++ ++ while ((c = getopt(argc, argv, "cht:v:")) != -1) { ++ switch (c) { ++ case 'c': ++ log_color(1); ++ break; ++ case 'h': ++ usage(basename(argv[0])); ++ exit(0); ++ case 'v': ++ log_verbosity(atoi(optarg)); ++ break; ++ default: ++ usage(basename(argv[0])); ++ exit(1); ++ } ++ } ++ ++ ksft_print_header(); ++ ksft_set_plan(2); ++ ksft_print_msg("%s: Test FUTEX2_WAITV\n", ++ basename(argv[0])); ++ ++ for (i = 0; i < NR_FUTEXES; i++) { ++ waitv[i].uaddr = &futexes[i]; ++ waitv[i].flags = FUTEX_32; ++ waitv[i].val = 0; ++ } ++ ++ /* Private waitv */ ++ if (pthread_create(&waiter, NULL, waiterfn, NULL)) ++ error("pthread_create failed\n", errno); ++ ++ usleep(WAKE_WAIT_US); ++ ++ res = futex2_wake(waitv[NR_FUTEXES - 1].uaddr, 1, FUTEX_32); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_waitv private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_waitv private succeeds\n"); ++ } ++ ++ /* Shared waitv */ ++ for (i = 0; i < NR_FUTEXES; i++) { ++ int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); ++ ++ if (shm_id < 0) { ++ perror("shmget"); ++ exit(1); ++ } ++ ++ unsigned int *shared_data = shmat(shm_id, NULL, 0); ++ ++ *shared_data = 0; ++ waitv[i].uaddr = shared_data; ++ waitv[i].flags = FUTEX_32 | FUTEX_SHARED_FLAG; ++ waitv[i].val = 0; ++ } ++ ++ if (pthread_create(&waiter, NULL, waiterfn, NULL)) ++ error("pthread_create failed\n", errno); ++ ++ usleep(WAKE_WAIT_US); ++ ++ res = futex2_wake(waitv[NR_FUTEXES - 1].uaddr, 1, FUTEX_32 | FUTEX_SHARED_FLAG); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_waitv shared returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_waitv shared succeeds\n"); ++ } ++ ++ for (i = 0; i < NR_FUTEXES; i++) ++ shmdt(waitv[i].uaddr); ++ ++ ksft_print_cnts(); ++ return ret; ++} +diff --git a/tools/testing/selftests/futex/functional/run.sh b/tools/testing/selftests/futex/functional/run.sh +index 3730159c865a..18b3883d7236 100755 +--- a/tools/testing/selftests/futex/functional/run.sh ++++ b/tools/testing/selftests/futex/functional/run.sh +@@ -76,3 +76,6 @@ echo + + echo + ./futex2_wait $COLOR ++ ++echo ++./futex2_waitv $COLOR +diff --git a/tools/testing/selftests/futex/include/futex2test.h b/tools/testing/selftests/futex/include/futex2test.h +index e724d56b917e..31979afc486f 100644 +--- a/tools/testing/selftests/futex/include/futex2test.h ++++ b/tools/testing/selftests/futex/include/futex2test.h +@@ -28,6 +28,19 @@ + # define FUTEX_32 2 + #endif + ++#ifndef FUTEX_SHARED_FLAG ++#define FUTEX_SHARED_FLAG 8 ++#endif ++ ++#ifndef FUTEX_WAITV_MAX ++#define FUTEX_WAITV_MAX 128 ++struct futex_waitv { ++ void *uaddr; ++ unsigned int val; ++ unsigned int flags; ++}; ++#endif ++ + /* + * - Y2038 section for 32-bit applications - + * +@@ -77,3 +90,16 @@ static inline int futex2_wake(volatile void *uaddr, unsigned int nr, unsigned lo + { + return syscall(__NR_futex_wake, uaddr, nr, flags); + } ++ ++/** ++ * futex2_waitv - Wait at multiple futexes, wake on any ++ * @waiters: Array of waiters ++ * @nr_waiters: Length of waiters array ++ * @flags: Operation flags ++ * @timo: Optional timeout for operation ++ */ ++static inline int futex2_waitv(volatile struct futex_waitv *waiters, unsigned long nr_waiters, ++ unsigned long flags, struct timespec64 *timo) ++{ ++ return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, timo); ++} +-- +GitLab + +From c6f8ed51da9411d893ea5efe6ba3cba4624cfda5 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:02 -0300 +Subject: [PATCH] selftests: futex2: Add requeue test +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Add testing for futex_requeue(). The first test just requeue from one +waiter to another one, and wake it. The second performs both wake and +requeue, and we check return values to see if the operation +woke/requeued the expected number of waiters. + +Signed-off-by: André Almeida +--- + .../selftests/futex/functional/.gitignore | 1 + + .../selftests/futex/functional/Makefile | 3 +- + .../futex/functional/futex2_requeue.c | 164 ++++++++++++++++++ + .../selftests/futex/include/futex2test.h | 16 ++ + 4 files changed, 183 insertions(+), 1 deletion(-) + create mode 100644 tools/testing/selftests/futex/functional/futex2_requeue.c + +diff --git a/tools/testing/selftests/futex/functional/.gitignore b/tools/testing/selftests/futex/functional/.gitignore +index d0b8f637b786..af7557e821da 100644 +--- a/tools/testing/selftests/futex/functional/.gitignore ++++ b/tools/testing/selftests/futex/functional/.gitignore +@@ -8,3 +8,4 @@ futex_wait_uninitialized_heap + futex_wait_wouldblock + futex2_wait + futex2_waitv ++futex2_requeue +diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile +index 09c08ccdeaf2..3ccb9ea58ddd 100644 +--- a/tools/testing/selftests/futex/functional/Makefile ++++ b/tools/testing/selftests/futex/functional/Makefile +@@ -17,7 +17,8 @@ TEST_GEN_FILES := \ + futex_wait_uninitialized_heap \ + futex_wait_private_mapped_file \ + futex2_wait \ +- futex2_waitv ++ futex2_waitv \ ++ futex2_requeue + + TEST_PROGS := run.sh + +diff --git a/tools/testing/selftests/futex/functional/futex2_requeue.c b/tools/testing/selftests/futex/functional/futex2_requeue.c +new file mode 100644 +index 000000000000..1bc3704dc8c2 +--- /dev/null ++++ b/tools/testing/selftests/futex/functional/futex2_requeue.c +@@ -0,0 +1,164 @@ ++// SPDX-License-Identifier: GPL-2.0-or-later ++/****************************************************************************** ++ * ++ * Copyright Collabora Ltd., 2021 ++ * ++ * DESCRIPTION ++ * Test requeue mechanism of futex2, using 32bit sized futexes. ++ * ++ * AUTHOR ++ * André Almeida ++ * ++ * HISTORY ++ * 2021-Feb-5: Initial version by André ++ * ++ *****************************************************************************/ ++ ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include ++#include "futex2test.h" ++#include "logging.h" ++ ++#define TEST_NAME "futex2-wait" ++#define timeout_ns 30000000 ++#define WAKE_WAIT_US 10000 ++volatile futex_t *f1; ++ ++void usage(char *prog) ++{ ++ printf("Usage: %s\n", prog); ++ printf(" -c Use color\n"); ++ printf(" -h Display this help message\n"); ++ printf(" -v L Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n", ++ VQUIET, VCRITICAL, VINFO); ++} ++ ++void *waiterfn(void *arg) ++{ ++ struct timespec64 to64; ++ ++ /* setting absolute timeout for futex2 */ ++ if (gettime64(CLOCK_MONOTONIC, &to64)) ++ error("gettime64 failed\n", errno); ++ ++ to64.tv_nsec += timeout_ns; ++ ++ if (to64.tv_nsec >= 1000000000) { ++ to64.tv_sec++; ++ to64.tv_nsec -= 1000000000; ++ } ++ ++ if (futex2_wait(f1, *f1, FUTEX_32, &to64)) ++ printf("waiter failed errno %d\n", errno); ++ ++ return NULL; ++} ++ ++int main(int argc, char *argv[]) ++{ ++ pthread_t waiter[10]; ++ int res, ret = RET_PASS; ++ int c, i; ++ volatile futex_t _f1 = 0; ++ volatile futex_t f2 = 0; ++ struct futex_requeue r1, r2; ++ ++ f1 = &_f1; ++ ++ r1.flags = FUTEX_32; ++ r2.flags = FUTEX_32; ++ ++ r1.uaddr = f1; ++ r2.uaddr = &f2; ++ ++ while ((c = getopt(argc, argv, "cht:v:")) != -1) { ++ switch (c) { ++ case 'c': ++ log_color(1); ++ break; ++ case 'h': ++ usage(basename(argv[0])); ++ exit(0); ++ case 'v': ++ log_verbosity(atoi(optarg)); ++ break; ++ default: ++ usage(basename(argv[0])); ++ exit(1); ++ } ++ } ++ ++ ksft_print_header(); ++ ksft_set_plan(2); ++ ksft_print_msg("%s: Test FUTEX2_REQUEUE\n", ++ basename(argv[0])); ++ ++ /* ++ * Requeue a waiter from f1 to f2, and wake f2. ++ */ ++ if (pthread_create(&waiter[0], NULL, waiterfn, NULL)) ++ error("pthread_create failed\n", errno); ++ ++ usleep(WAKE_WAIT_US); ++ ++ res = futex2_requeue(&r1, &r2, 0, 1, 0, 0); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_requeue private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } ++ ++ ++ info("Calling private futex2_wake on f2: %u @ %p with val=%u\n", f2, &f2, f2); ++ res = futex2_wake(&f2, 1, FUTEX_32); ++ if (res != 1) { ++ ksft_test_result_fail("futex2_requeue private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_requeue simple succeeds\n"); ++ } ++ ++ ++ /* ++ * Create 10 waiters at f1. At futex_requeue, wake 3 and requeue 7. ++ * At futex_wake, wake INT_MAX (should be exaclty 7). ++ */ ++ for (i = 0; i < 10; i++) { ++ if (pthread_create(&waiter[i], NULL, waiterfn, NULL)) ++ error("pthread_create failed\n", errno); ++ } ++ ++ usleep(WAKE_WAIT_US); ++ ++ res = futex2_requeue(&r1, &r2, 3, 7, 0, 0); ++ if (res != 10) { ++ ksft_test_result_fail("futex2_requeue private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } ++ ++ res = futex2_wake(&f2, INT_MAX, FUTEX_32); ++ if (res != 7) { ++ ksft_test_result_fail("futex2_requeue private returned: %d %s\n", ++ res ? errno : res, ++ res ? strerror(errno) : ""); ++ ret = RET_FAIL; ++ } else { ++ ksft_test_result_pass("futex2_requeue succeeds\n"); ++ } ++ ++ ksft_print_cnts(); ++ return ret; ++} +diff --git a/tools/testing/selftests/futex/include/futex2test.h b/tools/testing/selftests/futex/include/futex2test.h +index 31979afc486f..e2635006b1a9 100644 +--- a/tools/testing/selftests/futex/include/futex2test.h ++++ b/tools/testing/selftests/futex/include/futex2test.h +@@ -103,3 +103,19 @@ static inline int futex2_waitv(volatile struct futex_waitv *waiters, unsigned lo + { + return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, timo); + } ++ ++/** ++ * futex2_requeue - Wake futexes at uaddr1 and requeue from uaddr1 to uaddr2 ++ * @uaddr1: Original address to wake and requeue from ++ * @uaddr2: Address to requeue to ++ * @nr_wake: Number of futexes to wake at uaddr1 before requeuing ++ * @nr_requeue: Number of futexes to requeue from uaddr1 to uaddr2 ++ * @cmpval: If (uaddr1->uaddr != cmpval), return immediatally ++ * @flgas: Operation flags ++ */ ++static inline int futex2_requeue(struct futex_requeue *uaddr1, struct futex_requeue *uaddr2, ++ unsigned int nr_wake, unsigned int nr_requeue, ++ unsigned int cmpval, unsigned long flags) ++{ ++ return syscall(__NR_futex_requeue, uaddr1, uaddr2, nr_wake, nr_requeue, cmpval, flags); ++} +-- +GitLab + +From 7a9cacbb174d26d4adfcca3efa5747bf6ae05fa2 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:02 -0300 +Subject: [PATCH] perf bench: Add futex2 benchmark tests +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Add support at the existing futex benchmarking code base to enable +futex2 calls. `perf bench` tests can be used not only as a way to +measure the performance of implementation, but also as stress testing +for the kernel infrastructure. + +Signed-off-by: André Almeida +--- + tools/arch/x86/include/asm/unistd_64.h | 12 ++++++ + tools/perf/bench/bench.h | 4 ++ + tools/perf/bench/futex-hash.c | 24 +++++++++-- + tools/perf/bench/futex-requeue.c | 57 ++++++++++++++++++++------ + tools/perf/bench/futex-wake-parallel.c | 41 +++++++++++++++--- + tools/perf/bench/futex-wake.c | 37 +++++++++++++---- + tools/perf/bench/futex.h | 47 +++++++++++++++++++++ + tools/perf/builtin-bench.c | 18 ++++++-- + 8 files changed, 206 insertions(+), 34 deletions(-) + +diff --git a/tools/arch/x86/include/asm/unistd_64.h b/tools/arch/x86/include/asm/unistd_64.h +index 4205ed4158bf..b65c51e8d675 100644 +--- a/tools/arch/x86/include/asm/unistd_64.h ++++ b/tools/arch/x86/include/asm/unistd_64.h +@@ -17,3 +17,15 @@ + #ifndef __NR_setns + #define __NR_setns 308 + #endif ++ ++#ifndef __NR_futex_wait ++# define __NR_futex_wait 443 ++#endif ++ ++#ifndef __NR_futex_wake ++# define __NR_futex_wake 444 ++#endif ++ ++#ifndef __NR_futex_requeue ++# define __NR_futex_requeue 446 ++#endif +diff --git a/tools/perf/bench/bench.h b/tools/perf/bench/bench.h +index eac36afab2b3..12346844b354 100644 +--- a/tools/perf/bench/bench.h ++++ b/tools/perf/bench/bench.h +@@ -38,9 +38,13 @@ int bench_mem_memcpy(int argc, const char **argv); + int bench_mem_memset(int argc, const char **argv); + int bench_mem_find_bit(int argc, const char **argv); + int bench_futex_hash(int argc, const char **argv); ++int bench_futex2_hash(int argc, const char **argv); + int bench_futex_wake(int argc, const char **argv); ++int bench_futex2_wake(int argc, const char **argv); + int bench_futex_wake_parallel(int argc, const char **argv); ++int bench_futex2_wake_parallel(int argc, const char **argv); + int bench_futex_requeue(int argc, const char **argv); ++int bench_futex2_requeue(int argc, const char **argv); + /* pi futexes */ + int bench_futex_lock_pi(int argc, const char **argv); + int bench_epoll_wait(int argc, const char **argv); +diff --git a/tools/perf/bench/futex-hash.c b/tools/perf/bench/futex-hash.c +index b65373ce5c4f..1068749af40c 100644 +--- a/tools/perf/bench/futex-hash.c ++++ b/tools/perf/bench/futex-hash.c +@@ -33,7 +33,7 @@ static unsigned int nthreads = 0; + static unsigned int nsecs = 10; + /* amount of futexes per thread */ + static unsigned int nfutexes = 1024; +-static bool fshared = false, done = false, silent = false; ++static bool fshared = false, done = false, silent = false, futex2 = false; + static int futex_flag = 0; + + struct timeval bench__start, bench__end, bench__runtime; +@@ -85,7 +85,10 @@ static void *workerfn(void *arg) + * such as internal waitqueue handling, thus enlarging + * the critical region protected by hb->lock. + */ +- ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag); ++ if (!futex2) ++ ret = futex_wait(&w->futex[i], 1234, NULL, futex_flag); ++ else ++ ret = futex2_wait(&w->futex[i], 1234, futex_flag, NULL); + if (!silent && + (!ret || errno != EAGAIN || errno != EWOULDBLOCK)) + warn("Non-expected futex return call"); +@@ -116,7 +119,7 @@ static void print_summary(void) + (int)bench__runtime.tv_sec); + } + +-int bench_futex_hash(int argc, const char **argv) ++static int __bench_futex_hash(int argc, const char **argv) + { + int ret = 0; + cpu_set_t cpuset; +@@ -148,7 +151,9 @@ int bench_futex_hash(int argc, const char **argv) + if (!worker) + goto errmem; + +- if (!fshared) ++ if (futex2) ++ futex_flag = FUTEX_32 | (fshared * FUTEX_SHARED_FLAG); ++ else if (!fshared) + futex_flag = FUTEX_PRIVATE_FLAG; + + printf("Run summary [PID %d]: %d threads, each operating on %d [%s] futexes for %d secs.\n\n", +@@ -228,3 +233,14 @@ int bench_futex_hash(int argc, const char **argv) + errmem: + err(EXIT_FAILURE, "calloc"); + } ++ ++int bench_futex_hash(int argc, const char **argv) ++{ ++ return __bench_futex_hash(argc, argv); ++} ++ ++int bench_futex2_hash(int argc, const char **argv) ++{ ++ futex2 = true; ++ return __bench_futex_hash(argc, argv); ++} +diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c +index 5fa23295ee5f..6cdd649b54f4 100644 +--- a/tools/perf/bench/futex-requeue.c ++++ b/tools/perf/bench/futex-requeue.c +@@ -2,8 +2,8 @@ + /* + * Copyright (C) 2013 Davidlohr Bueso + * +- * futex-requeue: Block a bunch of threads on futex1 and requeue them +- * on futex2, N at a time. ++ * futex-requeue: Block a bunch of threads on addr1 and requeue them ++ * on addr2, N at a time. + * + * This program is particularly useful to measure the latency of nthread + * requeues without waking up any tasks -- thus mimicking a regular futex_wait. +@@ -28,7 +28,10 @@ + #include + #include + +-static u_int32_t futex1 = 0, futex2 = 0; ++static u_int32_t addr1 = 0, addr2 = 0; ++ ++static struct futex_requeue rq1 = { .uaddr = &addr1, .flags = FUTEX_32 }; ++static struct futex_requeue rq2 = { .uaddr = &addr2, .flags = FUTEX_32 }; + + /* + * How many tasks to requeue at a time. +@@ -37,7 +40,7 @@ static u_int32_t futex1 = 0, futex2 = 0; + static unsigned int nrequeue = 1; + + static pthread_t *worker; +-static bool done = false, silent = false, fshared = false; ++static bool done = false, silent = false, fshared = false, futex2 = false; + static pthread_mutex_t thread_lock; + static pthread_cond_t thread_parent, thread_worker; + static struct stats requeuetime_stats, requeued_stats; +@@ -79,7 +82,11 @@ static void *workerfn(void *arg __maybe_unused) + pthread_cond_wait(&thread_worker, &thread_lock); + pthread_mutex_unlock(&thread_lock); + +- futex_wait(&futex1, 0, NULL, futex_flag); ++ if (!futex2) ++ futex_wait(&addr1, 0, NULL, futex_flag); ++ else ++ futex2_wait(&addr1, 0, futex_flag, NULL); ++ + return NULL; + } + +@@ -111,7 +118,7 @@ static void toggle_done(int sig __maybe_unused, + done = true; + } + +-int bench_futex_requeue(int argc, const char **argv) ++static int __bench_futex_requeue(int argc, const char **argv) + { + int ret = 0; + unsigned int i, j; +@@ -139,15 +146,20 @@ int bench_futex_requeue(int argc, const char **argv) + if (!worker) + err(EXIT_FAILURE, "calloc"); + +- if (!fshared) ++ if (futex2) { ++ futex_flag = FUTEX_32 | (fshared * FUTEX_SHARED_FLAG); ++ rq1.flags |= FUTEX_SHARED_FLAG * fshared; ++ rq2.flags |= FUTEX_SHARED_FLAG * fshared; ++ } else if (!fshared) { + futex_flag = FUTEX_PRIVATE_FLAG; ++ } + + if (nrequeue > nthreads) + nrequeue = nthreads; + + printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), " + "%d at a time.\n\n", getpid(), nthreads, +- fshared ? "shared":"private", &futex1, &futex2, nrequeue); ++ fshared ? "shared":"private", &addr1, &addr2, nrequeue); + + init_stats(&requeued_stats); + init_stats(&requeuetime_stats); +@@ -176,11 +188,15 @@ int bench_futex_requeue(int argc, const char **argv) + gettimeofday(&start, NULL); + while (nrequeued < nthreads) { + /* +- * Do not wakeup any tasks blocked on futex1, allowing ++ * Do not wakeup any tasks blocked on addr1, allowing + * us to really measure futex_wait functionality. + */ +- nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0, +- nrequeue, futex_flag); ++ if (!futex2) ++ nrequeued += futex_cmp_requeue(&addr1, 0, &addr2, ++ 0, nrequeue, futex_flag); ++ else ++ nrequeued += futex2_requeue(&rq1, &rq2, ++ 0, nrequeue, 0, 0); + } + + gettimeofday(&end, NULL); +@@ -194,8 +210,12 @@ int bench_futex_requeue(int argc, const char **argv) + j + 1, nrequeued, nthreads, runtime.tv_usec / (double)USEC_PER_MSEC); + } + +- /* everybody should be blocked on futex2, wake'em up */ +- nrequeued = futex_wake(&futex2, nrequeued, futex_flag); ++ /* everybody should be blocked on addr2, wake'em up */ ++ if (!futex2) ++ nrequeued = futex_wake(&addr2, nrequeued, futex_flag); ++ else ++ nrequeued = futex2_wake(&addr2, nrequeued, futex_flag); ++ + if (nthreads != nrequeued) + warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads); + +@@ -220,3 +240,14 @@ int bench_futex_requeue(int argc, const char **argv) + usage_with_options(bench_futex_requeue_usage, options); + exit(EXIT_FAILURE); + } ++ ++int bench_futex_requeue(int argc, const char **argv) ++{ ++ return __bench_futex_requeue(argc, argv); ++} ++ ++int bench_futex2_requeue(int argc, const char **argv) ++{ ++ futex2 = true; ++ return __bench_futex_requeue(argc, argv); ++} +diff --git a/tools/perf/bench/futex-wake-parallel.c b/tools/perf/bench/futex-wake-parallel.c +index 6e6f5247e1fe..cac90fc0bfb3 100644 +--- a/tools/perf/bench/futex-wake-parallel.c ++++ b/tools/perf/bench/futex-wake-parallel.c +@@ -17,6 +17,12 @@ int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe + pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__); + return 0; + } ++ ++int bench_futex2_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused) ++{ ++ pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__); ++ return 0; ++} + #else /* HAVE_PTHREAD_BARRIER */ + /* For the CLR_() macros */ + #include +@@ -47,7 +53,7 @@ static unsigned int nwakes = 1; + static u_int32_t futex = 0; + + static pthread_t *blocked_worker; +-static bool done = false, silent = false, fshared = false; ++static bool done = false, silent = false, fshared = false, futex2 = false; + static unsigned int nblocked_threads = 0, nwaking_threads = 0; + static pthread_mutex_t thread_lock; + static pthread_cond_t thread_parent, thread_worker; +@@ -78,7 +84,11 @@ static void *waking_workerfn(void *arg) + + gettimeofday(&start, NULL); + +- waker->nwoken = futex_wake(&futex, nwakes, futex_flag); ++ if (!futex2) ++ waker->nwoken = futex_wake(&futex, nwakes, futex_flag); ++ else ++ waker->nwoken = futex2_wake(&futex, nwakes, futex_flag); ++ + if (waker->nwoken != nwakes) + warnx("couldn't wakeup all tasks (%d/%d)", + waker->nwoken, nwakes); +@@ -129,8 +139,13 @@ static void *blocked_workerfn(void *arg __maybe_unused) + pthread_mutex_unlock(&thread_lock); + + while (1) { /* handle spurious wakeups */ +- if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) +- break; ++ if (!futex2) { ++ if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR) ++ break; ++ } else { ++ if (futex2_wait(&futex, 0, futex_flag, NULL) != EINTR) ++ break; ++ } + } + + pthread_exit(NULL); +@@ -217,7 +232,7 @@ static void toggle_done(int sig __maybe_unused, + done = true; + } + +-int bench_futex_wake_parallel(int argc, const char **argv) ++static int __bench_futex_wake_parallel(int argc, const char **argv) + { + int ret = 0; + unsigned int i, j; +@@ -261,7 +276,9 @@ int bench_futex_wake_parallel(int argc, const char **argv) + if (!blocked_worker) + err(EXIT_FAILURE, "calloc"); + +- if (!fshared) ++ if (futex2) ++ futex_flag = FUTEX_32 | (fshared * FUTEX_SHARED_FLAG); ++ else if (!fshared) + futex_flag = FUTEX_PRIVATE_FLAG; + + printf("Run summary [PID %d]: blocking on %d threads (at [%s] " +@@ -321,4 +338,16 @@ int bench_futex_wake_parallel(int argc, const char **argv) + free(blocked_worker); + return ret; + } ++ ++int bench_futex_wake_parallel(int argc, const char **argv) ++{ ++ return __bench_futex_wake_parallel(argc, argv); ++} ++ ++int bench_futex2_wake_parallel(int argc, const char **argv) ++{ ++ futex2 = true; ++ return __bench_futex_wake_parallel(argc, argv); ++} ++ + #endif /* HAVE_PTHREAD_BARRIER */ +diff --git a/tools/perf/bench/futex-wake.c b/tools/perf/bench/futex-wake.c +index 6d217868f53c..546d2818eed8 100644 +--- a/tools/perf/bench/futex-wake.c ++++ b/tools/perf/bench/futex-wake.c +@@ -38,7 +38,7 @@ static u_int32_t futex1 = 0; + static unsigned int nwakes = 1; + + pthread_t *worker; +-static bool done = false, silent = false, fshared = false; ++static bool done = false, silent = false, fshared = false, futex2 = false; + static pthread_mutex_t thread_lock; + static pthread_cond_t thread_parent, thread_worker; + static struct stats waketime_stats, wakeup_stats; +@@ -68,8 +68,13 @@ static void *workerfn(void *arg __maybe_unused) + pthread_mutex_unlock(&thread_lock); + + while (1) { +- if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) +- break; ++ if (!futex2) { ++ if (futex_wait(&futex1, 0, NULL, futex_flag) != EINTR) ++ break; ++ } else { ++ if (futex2_wait(&futex1, 0, futex_flag, NULL) != EINTR) ++ break; ++ } + } + + pthread_exit(NULL); +@@ -117,7 +122,7 @@ static void toggle_done(int sig __maybe_unused, + done = true; + } + +-int bench_futex_wake(int argc, const char **argv) ++static int __bench_futex_wake(int argc, const char **argv) + { + int ret = 0; + unsigned int i, j; +@@ -147,7 +152,9 @@ int bench_futex_wake(int argc, const char **argv) + if (!worker) + err(EXIT_FAILURE, "calloc"); + +- if (!fshared) ++ if (futex2) ++ futex_flag = FUTEX_32 | (fshared * FUTEX_SHARED_FLAG); ++ else if (!fshared) + futex_flag = FUTEX_PRIVATE_FLAG; + + printf("Run summary [PID %d]: blocking on %d threads (at [%s] futex %p), " +@@ -179,9 +186,14 @@ int bench_futex_wake(int argc, const char **argv) + + /* Ok, all threads are patiently blocked, start waking folks up */ + gettimeofday(&start, NULL); +- while (nwoken != nthreads) +- nwoken += futex_wake(&futex1, nwakes, futex_flag); ++ while (nwoken != nthreads) { ++ if (!futex2) ++ nwoken += futex_wake(&futex1, nwakes, futex_flag); ++ else ++ nwoken += futex2_wake(&futex1, nwakes, futex_flag); ++ } + gettimeofday(&end, NULL); ++ + timersub(&end, &start, &runtime); + + update_stats(&wakeup_stats, nwoken); +@@ -211,3 +223,14 @@ int bench_futex_wake(int argc, const char **argv) + free(worker); + return ret; + } ++ ++int bench_futex_wake(int argc, const char **argv) ++{ ++ return __bench_futex_wake(argc, argv); ++} ++ ++int bench_futex2_wake(int argc, const char **argv) ++{ ++ futex2 = true; ++ return __bench_futex_wake(argc, argv); ++} +diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h +index 31b53cc7d5bc..6b2213cf3f64 100644 +--- a/tools/perf/bench/futex.h ++++ b/tools/perf/bench/futex.h +@@ -86,4 +86,51 @@ futex_cmp_requeue(u_int32_t *uaddr, u_int32_t val, u_int32_t *uaddr2, int nr_wak + return futex(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2, + val, opflags); + } ++ ++/** ++ * futex2_wait - Wait at uaddr if *uaddr == val, until timo. ++ * @uaddr: User address to wait for ++ * @val: Expected value at uaddr ++ * @flags: Operation options ++ * @timo: Optional timeout ++ * ++ * Return: 0 on success, error code otherwise ++ */ ++static inline int futex2_wait(volatile void *uaddr, unsigned long val, ++ unsigned long flags, struct timespec *timo) ++{ ++ return syscall(__NR_futex_wait, uaddr, val, flags, timo); ++} ++ ++/** ++ * futex2_wake - Wake a number of waiters waiting at uaddr ++ * @uaddr: Address to wake ++ * @nr: Number of waiters to wake ++ * @flags: Operation options ++ * ++ * Return: number of waked futexes ++ */ ++static inline int futex2_wake(volatile void *uaddr, unsigned int nr, unsigned long flags) ++{ ++ return syscall(__NR_futex_wake, uaddr, nr, flags); ++} ++ ++/** ++ * futex2_requeue - Requeue waiters from an address to another one ++ * @uaddr1: Address where waiters are currently waiting on ++ * @uaddr2: New address to wait ++ * @nr_wake: Number of waiters at uaddr1 to be wake ++ * @nr_requeue: After waking nr_wake, number of waiters to be requeued ++ * @cmpval: Expected value at uaddr1 ++ * @flags: Operation options ++ * ++ * Return: waked futexes + requeued futexes at uaddr1 ++ */ ++static inline int futex2_requeue(volatile struct futex_requeue *uaddr1, ++ volatile struct futex_requeue *uaddr2, ++ unsigned int nr_wake, unsigned int nr_requeue, ++ unsigned int cmpval, unsigned long flags) ++{ ++ return syscall(__NR_futex_requeue, uaddr1, uaddr2, nr_wake, nr_requeue, cmpval, flags); ++} + #endif /* _FUTEX_H */ +diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c +index 62a7b7420a44..e41a95ad2db6 100644 +--- a/tools/perf/builtin-bench.c ++++ b/tools/perf/builtin-bench.c +@@ -12,10 +12,11 @@ + * + * sched ... scheduler and IPC performance + * syscall ... System call performance +- * mem ... memory access performance +- * numa ... NUMA scheduling and MM performance +- * futex ... Futex performance +- * epoll ... Event poll performance ++ * mem ... memory access performance ++ * numa ... NUMA scheduling and MM performance ++ * futex ... Futex performance ++ * futex2 ... Futex2 performance ++ * epoll ... Event poll performance + */ + #include + #include "builtin.h" +@@ -75,6 +76,14 @@ static struct bench futex_benchmarks[] = { + { NULL, NULL, NULL } + }; + ++static struct bench futex2_benchmarks[] = { ++ { "hash", "Benchmark for futex2 hash table", bench_futex2_hash }, ++ { "wake", "Benchmark for futex2 wake calls", bench_futex2_wake }, ++ { "wake-parallel", "Benchmark for parallel futex2 wake calls", bench_futex2_wake_parallel }, ++ { "requeue", "Benchmark for futex2 requeue calls", bench_futex2_requeue }, ++ { NULL, NULL, NULL } ++}; ++ + #ifdef HAVE_EVENTFD_SUPPORT + static struct bench epoll_benchmarks[] = { + { "wait", "Benchmark epoll concurrent epoll_waits", bench_epoll_wait }, +@@ -105,6 +114,7 @@ static struct collection collections[] = { + { "numa", "NUMA scheduling and MM benchmarks", numa_benchmarks }, + #endif + {"futex", "Futex stressing benchmarks", futex_benchmarks }, ++ {"futex2", "Futex2 stressing benchmarks", futex2_benchmarks }, + #ifdef HAVE_EVENTFD_SUPPORT + {"epoll", "Epoll stressing benchmarks", epoll_benchmarks }, + #endif +-- +GitLab + +From dcd3dfa6c75d110174c948aadb14e41416a826dd Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:02 -0300 +Subject: [PATCH] kernel: Enable waitpid() for futex2 +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +To make pthreads works as expected if they are using futex2, wake +clear_child_tid with futex2 as well. This is make applications that uses +waitpid() (and clone(CLONE_CHILD_SETTID)) wake while waiting for the +child to terminate. Given that apps should not mix futex() and futex2(), +any correct app will trigger a harmless noop wakeup on the interface +that it isn't using. + +Signed-off-by: André Almeida +--- + +This commit is here for the intend to show what we need to do in order +to get a full NPTL working on top of futex2. It should be merged after +we talk to glibc folks on the details around the futex_wait() side. For +instance, we could use this as an opportunity to use private futexes or +8bit sized futexes, but both sides need to use the exactly same flags. +--- + include/linux/syscalls.h | 2 ++ + kernel/fork.c | 2 ++ + kernel/futex2.c | 30 ++++++++++++++++++------------ + 3 files changed, 22 insertions(+), 12 deletions(-) + +diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h +index b0675f236066..b07b7d4334a6 100644 +--- a/include/linux/syscalls.h ++++ b/include/linux/syscalls.h +@@ -1316,6 +1316,8 @@ int ksys_ipc(unsigned int call, int first, unsigned long second, + unsigned long third, void __user * ptr, long fifth); + int compat_ksys_ipc(u32 call, int first, int second, + u32 third, u32 ptr, u32 fifth); ++long ksys_futex_wake(void __user *uaddr, unsigned long nr_wake, ++ unsigned int flags); + + /* + * The following kernel syscall equivalents are just wrappers to fs-internal +diff --git a/kernel/fork.c b/kernel/fork.c +index d66cd1014211..e39846a73a43 100644 +--- a/kernel/fork.c ++++ b/kernel/fork.c +@@ -1308,6 +1308,8 @@ static void mm_release(struct task_struct *tsk, struct mm_struct *mm) + put_user(0, tsk->clear_child_tid); + do_futex(tsk->clear_child_tid, FUTEX_WAKE, + 1, NULL, NULL, 0, 0); ++ ksys_futex_wake(tsk->clear_child_tid, 1, ++ FUTEX_32 | FUTEX_SHARED_FLAG); + } + tsk->clear_child_tid = NULL; + } +diff --git a/kernel/futex2.c b/kernel/futex2.c +index 61b81b401e58..b92c3ca5e89f 100644 +--- a/kernel/futex2.c ++++ b/kernel/futex2.c +@@ -940,18 +940,8 @@ static inline bool futex_match(struct futex_key key1, struct futex_key key2) + key1.offset == key2.offset); + } + +-/** +- * sys_futex_wake - Wake a number of futexes waiting on an address +- * @uaddr: Address of futex to be woken up +- * @nr_wake: Number of futexes waiting in uaddr to be woken up +- * @flags: Flags for size and shared +- * +- * Wake `nr_wake` threads waiting at uaddr. +- * +- * Returns the number of woken threads on success, error code otherwise. +- */ +-SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, +- unsigned int, flags) ++long ksys_futex_wake(void __user *uaddr, unsigned long nr_wake, ++ unsigned int flags) + { + bool shared = (flags & FUTEX_SHARED_FLAG) ? true : false; + unsigned int size = flags & FUTEX_SIZE_MASK; +@@ -988,6 +978,22 @@ SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, + return ret; + } + ++/** ++ * sys_futex_wake - Wake a number of futexes waiting on an address ++ * @uaddr: Address of futex to be woken up ++ * @nr_wake: Number of futexes waiting in uaddr to be woken up ++ * @flags: Flags for size and shared ++ * ++ * Wake `nr_wake` threads waiting at uaddr. ++ * ++ * Returns the number of woken threads on success, error code otherwise. ++ */ ++SYSCALL_DEFINE3(futex_wake, void __user *, uaddr, unsigned int, nr_wake, ++ unsigned int, flags) ++{ ++ return ksys_futex_wake(uaddr, nr_wake, flags); ++} ++ + static void futex_double_unlock(struct futex_bucket *b1, struct futex_bucket *b2) + { + spin_unlock(&b1->lock); +-- +GitLab + +From 3fe11532bcb2560097e0f19bfd612ca4e19cd098 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Andr=C3=A9=20Almeida?= +Date: Fri, 5 Feb 2021 10:34:02 -0300 +Subject: [PATCH] futex2: Add sysfs entry for syscall numbers +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +In the course of futex2 development, it will be rebased on top of +different kernel releases, and the syscall number can change in this +process. Expose futex2 syscall number via sysfs so tools that are +experimenting with futex2 (like Proton/Wine) can test it and set the +syscall number at runtime, rather than setting it at compilation time. + +Signed-off-by: André Almeida +--- + kernel/futex2.c | 42 ++++++++++++++++++++++++++++++++++++++++++ + 1 file changed, 42 insertions(+) + +diff --git a/kernel/futex2.c b/kernel/futex2.c +index b92c3ca5e89f..d138340a3f7b 100644 +--- a/kernel/futex2.c ++++ b/kernel/futex2.c +@@ -1224,6 +1224,48 @@ SYSCALL_DEFINE6(futex_requeue, struct futex_requeue __user *, uaddr1, + return __futex_requeue(rq1, rq2, nr_wake, nr_requeue, cmpval, shared1, shared2); + } + ++static ssize_t wait_show(struct kobject *kobj, struct kobj_attribute *attr, ++ char *buf) ++{ ++ return sprintf(buf, "%u\n", __NR_futex_wait); ++ ++} ++static struct kobj_attribute futex2_wait_attr = __ATTR_RO(wait); ++ ++static ssize_t wake_show(struct kobject *kobj, struct kobj_attribute *attr, ++ char *buf) ++{ ++ return sprintf(buf, "%u\n", __NR_futex_wake); ++ ++} ++static struct kobj_attribute futex2_wake_attr = __ATTR_RO(wake); ++ ++static ssize_t waitv_show(struct kobject *kobj, struct kobj_attribute *attr, ++ char *buf) ++{ ++ return sprintf(buf, "%u\n", __NR_futex_waitv); ++ ++} ++static struct kobj_attribute futex2_waitv_attr = __ATTR_RO(waitv); ++ ++static struct attribute *futex2_sysfs_attrs[] = { ++ &futex2_wait_attr.attr, ++ &futex2_wake_attr.attr, ++ &futex2_waitv_attr.attr, ++ NULL, ++}; ++ ++static const struct attribute_group futex2_sysfs_attr_group = { ++ .attrs = futex2_sysfs_attrs, ++ .name = "futex2", ++}; ++ ++static int __init futex2_sysfs_init(void) ++{ ++ return sysfs_create_group(kernel_kobj, &futex2_sysfs_attr_group); ++} ++subsys_initcall(futex2_sysfs_init); ++ + static int __init futex2_init(void) + { + int i; +-- +GitLab