Messages in this thread | | | Date | Wed, 21 Feb 2007 13:06:06 -0800 | From | "Paul E. McKenney" <> | Subject | Re: freezer problems |
| |
On Wed, Feb 21, 2007 at 11:03:14PM +0300, Oleg Nesterov wrote: > 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.
This sounds much better than a a global lock to me! ;-)
Thanx, Paul - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |