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signal: retarget_shared_pending: optimize while_each_thread() loop

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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: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Oleg Nesterov 2011-04-27 19:50:21 +02:00
parent f646e227b8
commit fec9993db0
1 changed files with 15 additions and 4 deletions
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19
kernel/signal.c
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@ -2200,8 +2200,8 @@ relock:
/* /*
* It could be that complete_signal() picked us to notify about the * It could be that complete_signal() picked us to notify about the
* group-wide signal. Another thread should be notified now to take * group-wide signal. Other threads should be notified now to take
* the signal since we will not. * the shared signals in @which since we will not.
*/ */
static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which) 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; t = tsk;
while_each_thread(tsk, t) { while_each_thread(tsk, t) {
if (!signal_pending(t) && !(t->flags & PF_EXITING)) if (t->flags & PF_EXITING)
recalc_sigpending_and_wake(t); 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;
} }
} }