| Date | Sun, 28 Aug 2011 19:56:01 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 09/16] freezer: make freezing indicate freeze condition in effect |
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On 08/19, Tejun Heo wrote: > > This patch makes freezing indicate that freeze condition is in effect. > A task enters and stays frozen if freezing. This makes PF_FROZEN > manipulation done only by the task itself and prevents wakeup from > __thaw_task() leaking outside of refrigerator.
but this looks racy.
> @@ -44,7 +48,7 @@ bool __refrigerator(bool check_kthr_stop) > > for (;;) { > set_current_state(TASK_UNINTERRUPTIBLE); > - if (!frozen(current) || > + if (!freezing(current) || > (check_kthr_stop && kthread_should_stop())) > break; > was_frozen = true; > @@ -54,6 +58,11 @@ bool __refrigerator(bool check_kthr_stop) > /* Remove the accounting blocker */ > current->flags &= ~PF_FREEZING; > > + /* leave FROZEN */ > + spin_lock_irq(&freezer_lock); > + current->flags &= ~PF_FROZEN; > + spin_unlock_irq(&freezer_lock);
What if freezing() is true again when we are going to clear PF_FROZEN?
In this case the 2nd try_to_freeze_tasks() can see this task as already frozen and return success while it is going to run.
Oleg.
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