signal: retarget_shared_pending: consider shared/unblocked signals only

exit_signals() checks signal_pending() before retarget_shared_pending() but
this is suboptimal. We can avoid the while_each_thread() loop in case when
there are no shared signals visible to us.

Add the "shared_pending.signal & ~blocked" check. We don't use tsk->blocked
directly but pass ~blocked as an argument, this is needed for the next patch.

Note: we can optimize this more. while_each_thread(t) can check t->blocked
into account and stop after every pending signal has the new target, see the
next patch.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>
Acked-by: Tejun Heo <tj@kernel.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 5341e2141904..06214b55dc5e 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2203,10 +2203,15 @@ relock:
  * group-wide signal. Another thread should be notified now to take
  * the signal since we will not.
  */
-static void retarget_shared_pending(struct task_struct *tsk)
+static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
 {
+        sigset_t retarget;
         struct task_struct *t;
 
+        sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
+        if (sigisemptyset(&retarget))
+                return;
+
         t = tsk;
         while_each_thread(tsk, t) {
                 if (!signal_pending(t) && !(t->flags & PF_EXITING))
@@ -2217,6 +2222,7 @@ static void retarget_shared_pending(struct task_struct *tsk)
 void exit_signals(struct task_struct *tsk)
 {
         int group_stop = 0;
+        sigset_t unblocked;
 
         if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
                 tsk->flags |= PF_EXITING;
@@ -2232,7 +2238,9 @@ void exit_signals(struct task_struct *tsk)
         if (!signal_pending(tsk))
                 goto out;
 
-        retarget_shared_pending(tsk);
+        unblocked = tsk->blocked;
+        signotset(&unblocked);
+        retarget_shared_pending(tsk, &unblocked);
 
         if (unlikely(tsk->group_stop & GROUP_STOP_PENDING) &&
             task_participate_group_stop(tsk))