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Commit fec9993d authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

signal: retarget_shared_pending: optimize while_each_thread() loop 



retarget_shared_pending() blindly does recalc_sigpending_and_wake() for
every sub-thread, this is suboptimal. We can check t->blocked and stop
looping once every bit in shared_pending has the new target.

Note: we do not take task_is_stopped_or_traced(t) into account, we are
not trying to speed up the signal delivery or to avoid the unnecessary
(but harmless) signal_wake_up(0) in this unlikely case.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarMatt Fleming <matt.fleming@linux.intel.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
parent f646e227

kernel/signal.c

+15 −4
Original line number Diff line number Diff line
@@ -2200,8 +2200,8 @@ int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka, 


/*

 * It could be that complete_signal() picked us to notify about the

 * group-wide signal. Another thread should be notified now to take

 * the signal since we will not.

 * group-wide signal. Other threads should be notified now to take

 * the shared signals in @which since we will not.

 */

static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)

{
@@ -2214,8 +2214,19 @@ static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which) 


	t = tsk;

	while_each_thread(tsk, t) {

		if (!signal_pending(t) && !(t->flags & PF_EXITING))

			recalc_sigpending_and_wake(t);

		if (t->flags & PF_EXITING)

			continue;



		if (!has_pending_signals(&retarget, &t->blocked))

			continue;

		/* Remove the signals this thread can handle. */

		sigandsets(&retarget, &retarget, &t->blocked);



		if (!signal_pending(t))

			signal_wake_up(t, 0);



		if (sigisemptyset(&retarget))

			break;

	}

}