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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 12:33:35 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 12:33:35 -0800 |
commit | 005b2a9dc819a1265a8c765595f8f6d88d6173d9 (patch) | |
tree | 688107572f6b3e017fc7ccf54f552c6a30441a79 /arch/alpha | |
parent | 5ee863bec794f30bdf7fdf57ce0d9f579b0d1aa3 (diff) | |
parent | 355fb9e2b78e78b38ec00f5cd9b05c6aceb98335 (diff) | |
download | linux-005b2a9dc819a1265a8c765595f8f6d88d6173d9.tar.gz |
Merge tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block
Pull TIF_NOTIFY_SIGNAL updates from Jens Axboe: "This sits on top of of the core entry/exit and x86 entry branch from the tip tree, which contains the generic and x86 parts of this work. Here we convert the rest of the archs to support TIF_NOTIFY_SIGNAL. With that done, we can get rid of JOBCTL_TASK_WORK from task_work and signal.c, and also remove a deadlock work-around in io_uring around knowing that signal based task_work waking is invoked with the sighand wait queue head lock. The motivation for this work is to decouple signal notify based task_work, of which io_uring is a heavy user of, from sighand. The sighand lock becomes a huge contention point, particularly for threaded workloads where it's shared between threads. Even outside of threaded applications it's slower than it needs to be. Roman Gershman <romger@amazon.com> reported that his networked workload dropped from 1.6M QPS at 80% CPU to 1.0M QPS at 100% CPU after io_uring was changed to use TIF_NOTIFY_SIGNAL. The time was all spent hammering on the sighand lock, showing 57% of the CPU time there [1]. There are further cleanups possible on top of this. One example is TIF_PATCH_PENDING, where a patch already exists to use TIF_NOTIFY_SIGNAL instead. Hopefully this will also lead to more consolidation, but the work stands on its own as well" [1] https://github.com/axboe/liburing/issues/215 * tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block: (28 commits) io_uring: remove 'twa_signal_ok' deadlock work-around kernel: remove checking for TIF_NOTIFY_SIGNAL signal: kill JOBCTL_TASK_WORK io_uring: JOBCTL_TASK_WORK is no longer used by task_work task_work: remove legacy TWA_SIGNAL path sparc: add support for TIF_NOTIFY_SIGNAL riscv: add support for TIF_NOTIFY_SIGNAL nds32: add support for TIF_NOTIFY_SIGNAL ia64: add support for TIF_NOTIFY_SIGNAL h8300: add support for TIF_NOTIFY_SIGNAL c6x: add support for TIF_NOTIFY_SIGNAL alpha: add support for TIF_NOTIFY_SIGNAL xtensa: add support for TIF_NOTIFY_SIGNAL arm: add support for TIF_NOTIFY_SIGNAL microblaze: add support for TIF_NOTIFY_SIGNAL hexagon: add support for TIF_NOTIFY_SIGNAL csky: add support for TIF_NOTIFY_SIGNAL openrisc: add support for TIF_NOTIFY_SIGNAL sh: add support for TIF_NOTIFY_SIGNAL um: add support for TIF_NOTIFY_SIGNAL ...
Diffstat (limited to 'arch/alpha')
-rw-r--r-- | arch/alpha/include/asm/thread_info.h | 2 | ||||
-rw-r--r-- | arch/alpha/kernel/entry.S | 2 | ||||
-rw-r--r-- | arch/alpha/kernel/signal.c | 2 |
3 files changed, 4 insertions, 2 deletions
diff --git a/arch/alpha/include/asm/thread_info.h b/arch/alpha/include/asm/thread_info.h index 807d7b9a1860..2592356e3215 100644 --- a/arch/alpha/include/asm/thread_info.h +++ b/arch/alpha/include/asm/thread_info.h @@ -62,6 +62,7 @@ register struct thread_info *__current_thread_info __asm__("$8"); #define TIF_SIGPENDING 2 /* signal pending */ #define TIF_NEED_RESCHED 3 /* rescheduling necessary */ #define TIF_SYSCALL_AUDIT 4 /* syscall audit active */ +#define TIF_NOTIFY_SIGNAL 5 /* signal notifications exist */ #define TIF_DIE_IF_KERNEL 9 /* dik recursion lock */ #define TIF_MEMDIE 13 /* is terminating due to OOM killer */ #define TIF_POLLING_NRFLAG 14 /* idle is polling for TIF_NEED_RESCHED */ @@ -71,6 +72,7 @@ register struct thread_info *__current_thread_info __asm__("$8"); #define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED) #define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME) #define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT) +#define _TIF_NOTIFY_SIGNAL (1<<TIF_NOTIFY_SIGNAL) #define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG) /* Work to do on interrupt/exception return. */ diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S index 2e09248f8324..e227f3a29a43 100644 --- a/arch/alpha/kernel/entry.S +++ b/arch/alpha/kernel/entry.S @@ -544,7 +544,7 @@ $ret_success: .align 4 .type work_pending, @function work_pending: - and $17, _TIF_NOTIFY_RESUME | _TIF_SIGPENDING, $2 + and $17, _TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL, $2 bne $2, $work_notifysig $work_resched: diff --git a/arch/alpha/kernel/signal.c b/arch/alpha/kernel/signal.c index 3739efce1ec0..948b89789da8 100644 --- a/arch/alpha/kernel/signal.c +++ b/arch/alpha/kernel/signal.c @@ -527,7 +527,7 @@ do_work_pending(struct pt_regs *regs, unsigned long thread_flags, schedule(); } else { local_irq_enable(); - if (thread_flags & _TIF_SIGPENDING) { + if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) { do_signal(regs, r0, r19); r0 = 0; } else { |