pi-futex: set PF_EXITING without taking ->pi_lock

It is a bit annoying that do_exit() takes ->pi_lock to set PF_EXITING. All we need is to synchronize with lookup_pi_state() which saw this task without PF_EXITING under ->pi_lock. Change do_exit() to use spin_unlock_wait(). Signed-off-by: Oleg Nesterov <[email protected]> Acked-by: Ingo Molnar <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
kevsmith · Oct 17, 2007 · d2ee719 · d2ee719
1 parent 7917ff9
commit d2ee719
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/kernel/exit.c b/kernel/exit.c
@@ -931,13 +931,13 @@ fastcall NORET_TYPE void do_exit(long code)
 		schedule();
 	}
 
+	tsk->flags |= PF_EXITING;
 	/*
 	 * tsk->flags are checked in the futex code to protect against
 	 * an exiting task cleaning up the robust pi futexes.
 	 */
-	spin_lock_irq(&tsk->pi_lock);
-	tsk->flags |= PF_EXITING;
-	spin_unlock_irq(&tsk->pi_lock);
+	smp_mb();
+	spin_unlock_wait(&tsk->pi_lock);
 
 	if (unlikely(in_atomic()))
 		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",