From 8a56f26607418ab517476de4a27e38be51f6fbca Mon Sep 17 00:00:00 2001 From: Mateusz Guzik Date: Mon, 3 Mar 2025 14:49:08 +0100 Subject: [PATCH] signal: avoid clearing TIF_SIGPENDING in recalc_sigpending() if unset 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 Acked-by: Oleg Nesterov Signed-off-by: Andrew Morton --- kernel/signal.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 875e97f6205a..ce3fae2f1fb5 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -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); -- 2.50.1