On 02/21, Rafael J. Wysocki wrote: > > On Wednesday, 21 February 2007 19:14, Paul E. McKenney wrote: > > On Tue, Feb 20, 2007 at 07:29:01PM +0100, Rafael J. Wysocki wrote: > > > On Tuesday, 20 February 2007 01:32, Rafael J. Wysocki wrote: > > > > On Tuesday, 20 February 2007 01:12, Oleg Nesterov wrote: > > > > Hm. In the case discussed above we have a task that's right before > > > > calling > > > > frozen_process(), so we can't thaw it, because it's not frozen. It > > > > will be > > > > frozen just in a while, but try_to_freeze_tasks() and thaw_tasks() have > > > > no > > > > way to check this. > > > > > > > > I think to close this race the refrigerator should check TIF_FREEZE and > > > > set > > > > PF_FROZEN _and_ reset TIF_FREEZE under a lock
I personally think this is good. Not only this allows us to close the race, I think we can do more. > that would also have to > be > > > > taken by try_to_freeze_tasks() in the beginning of the error path. > > > > This will > > > > ensure that all tasks either freeze themselves before the error path in > > > > try_to_freeze_tasks() is executed, or remain unfrozen. How about take this lock in thaw_tasks() instead/too ? Currently we need a separate loop in thaw_tasks() to handle PF_FREEZER_SKIP. This means that PF_FREEZER_SKIP is not so generic: thaw_tasks() can't tolerate if such a task was woken in between. What if we change thaw_process() to clear TIF_FREEZE ? Note also that we can use task_lock() instead of global refrigerator_lock. This means that thaw_process() should take it too, probably this is slowdown, but I think not too much because thaw_process() is going to write to p->flags anyway. In this case thaw_process() works perfectly as cancel_freezing_and_thaw() and can be used to fix exec/coredump in future. Thoughts? Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
