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authorLinus Torvalds <torvalds@linux-foundation.org>2020-12-16 23:33:35 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-16 23:33:35 +0300
commit005b2a9dc819a1265a8c765595f8f6d88d6173d9 (patch)
tree688107572f6b3e017fc7ccf54f552c6a30441a79 /arch/um
parent5ee863bec794f30bdf7fdf57ce0d9f579b0d1aa3 (diff)
parent355fb9e2b78e78b38ec00f5cd9b05c6aceb98335 (diff)
downloadlinux-005b2a9dc819a1265a8c765595f8f6d88d6173d9.tar.xz
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/um')
-rw-r--r--arch/um/include/asm/thread_info.h2
-rw-r--r--arch/um/kernel/process.c3
2 files changed, 4 insertions, 1 deletions
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index 4c19ce4c49f1..3b1cb8b3b186 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -57,6 +57,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
#define TIF_SIGPENDING 1 /* signal pending */
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
+#define TIF_NOTIFY_SIGNAL 3 /* signal notifications exist */
#define TIF_RESTART_BLOCK 4
#define TIF_MEMDIE 5 /* is terminating due to OOM killer */
#define TIF_SYSCALL_AUDIT 6
@@ -67,6 +68,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
+#define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 9505a7e87396..0fcdc374a9a1 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -99,7 +99,8 @@ void interrupt_end(void)
if (need_resched())
schedule();
- if (test_thread_flag(TIF_SIGPENDING))
+ if (test_thread_flag(TIF_SIGPENDING) ||
+ test_thread_flag(TIF_NOTIFY_SIGNAL))
do_signal(regs);
if (test_thread_flag(TIF_NOTIFY_RESUME))
tracehook_notify_resume(regs);