On 08/09, Liao Chang wrote:
>
> Since clearing a bit in thread_info is an atomic operation, the spinlock
> is redundant and can be removed, reducing lock contention is good for
> performance.
My ack still stays, but let me add some notes...
sighand->siglock doesn't protect clear_bit() per se. It was used to not
break the "the state of TIF_SIGPENDING of every thread is stable with
sighand->siglock held" rule.
But we already have the lockless users of clear_thread_flag(TIF_SIGPENDING)
(some if not most of them look buggy), and afaics in this (very special)
case it should be fine.
Oleg.
> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Signed-off-by: Liao Chang <liaochang1@xxxxxxxxxx>
> ---
> kernel/events/uprobes.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 73cc47708679..76a51a1f51e2 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1979,9 +1979,7 @@ bool uprobe_deny_signal(void)
> WARN_ON_ONCE(utask->state != UTASK_SSTEP);
>
> if (task_sigpending(t)) {
> - spin_lock_irq(&t->sighand->siglock);
> clear_tsk_thread_flag(t, TIF_SIGPENDING);
> - spin_unlock_irq(&t->sighand->siglock);
>
> if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
> utask->state = UTASK_SSTEP_TRAPPED;
> --
> 2.34.1
>
