path: root/arch/arc
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authorLinus Torvalds <>2020-12-16 12:33:35 -0800
committerLinus Torvalds <>2020-12-16 12:33:35 -0800
commit005b2a9dc819a1265a8c765595f8f6d88d6173d9 (patch)
tree688107572f6b3e017fc7ccf54f552c6a30441a79 /arch/arc
parent5ee863bec794f30bdf7fdf57ce0d9f579b0d1aa3 (diff)
parent355fb9e2b78e78b38ec00f5cd9b05c6aceb98335 (diff)
Merge tag 'tif-task_work.arch-2020-12-14' of git://
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 <> 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] * tag 'tif-task_work.arch-2020-12-14' of git:// (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/arc')
3 files changed, 6 insertions, 3 deletions
diff --git a/arch/arc/include/asm/thread_info.h b/arch/arc/include/asm/thread_info.h
index f9eef0e8f0b7..c0942c24d401 100644
--- a/arch/arc/include/asm/thread_info.h
+++ b/arch/arc/include/asm/thread_info.h
@@ -79,6 +79,7 @@ static inline __attribute_const__ struct thread_info *current_thread_info(void)
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_SYSCALL_AUDIT 4 /* syscall auditing active */
+#define TIF_NOTIFY_SIGNAL 5 /* signal notifications exist */
#define TIF_SYSCALL_TRACE 15 /* syscall trace active */
/* true if poll_idle() is polling TIF_NEED_RESCHED */
@@ -89,11 +90,12 @@ static inline __attribute_const__ struct thread_info *current_thread_info(void)
/* work to do on interrupt/exception return */
* _TIF_ALLWORK_MASK includes SYSCALL_TRACE, but we don't need it.
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index ea00c8a17f07..1f5308abf36d 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -307,7 +307,8 @@ resume_user_mode_begin:
mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume()
- bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume
+ bz .Lchk_notify_resume
; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
; in pt_reg since the "C" ABI (kernel code) will automatically
diff --git a/arch/arc/kernel/signal.c b/arch/arc/kernel/signal.c
index 2be55fb96d87..a78d8f745a67 100644
--- a/arch/arc/kernel/signal.c
+++ b/arch/arc/kernel/signal.c
@@ -362,7 +362,7 @@ void do_signal(struct pt_regs *regs)
restart_scall = in_syscall(regs) && syscall_restartable(regs);
- if (get_signal(&ksig)) {
+ if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) {
if (restart_scall) {
arc_restart_syscall(&ksig.ka, regs);
syscall_wont_restart(regs); /* No more restarts */