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authorLinus Torvalds <torvalds@linux-foundation.org>2020-12-16 12:33:35 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-16 12:33:35 -0800
commit005b2a9dc819a1265a8c765595f8f6d88d6173d9 (patch)
tree688107572f6b3e017fc7ccf54f552c6a30441a79 /arch/alpha/kernel
parent5ee863bec794f30bdf7fdf57ce0d9f579b0d1aa3 (diff)
parent355fb9e2b78e78b38ec00f5cd9b05c6aceb98335 (diff)
downloadlinux-stericsson-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/kernel')
-rw-r--r--arch/alpha/kernel/entry.S2
-rw-r--r--arch/alpha/kernel/signal.c2
2 files changed, 2 insertions, 2 deletions
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 {