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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 <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-10-16 23:26:47 -07:00 committed by Linus Torvalds
parent 7917ff9a4c
commit d2ee7198cc
1 changed files with 3 additions and 3 deletions
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6
kernel/exit.c
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@ -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",