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signal: avoid clearing TIF_SIGPENDING in recalc_sigpending() if unset

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Clearing is an atomic op and the flag is not set most of the time.

When creating and destroying threads in the same process with the pthread
family, the primary bottleneck is calls to sigprocmask which take the
process-wide sighand lock.

Avoiding the atomic gives me a 2% bump in start/teardown rate at 24-core
scale.

[akpm@linux-foundation.org: add unlikely() as well]
Link: https://lkml.kernel.org/r/20250303134908.423242-1-mjguzik@gmail.com
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Mateusz Guzik 2025-03-03 14:49:08 +01:00 • committed by Andrew Morton
parent e0349c46cb
commit 8a56f26607
1 changed files with 4 additions and 3 deletions
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7
kernel/signal.c
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@ -176,9 +176,10 @@ static bool recalc_sigpending_tsk(struct task_struct *t)
void recalc_sigpending(void)
{
if (!recalc_sigpending_tsk(current) && !freezing(current))
clear_thread_flag(TIF_SIGPENDING);
if (!recalc_sigpending_tsk(current) && !freezing(current)) {
if (unlikely(test_thread_flag(TIF_SIGPENDING)))
clear_thread_flag(TIF_SIGPENDING);
}
}
EXPORT_SYMBOL(recalc_sigpending);