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: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index 06214b5..707736e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2200,8 +2200,8 @@
/*
* 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 @@
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;
}
}