Messages in this thread | | | Date | Mon, 24 May 2010 12:13:40 +0530 | From | "Amit K. Arora" <> | Subject | Re: [PATCH v2] Make sure timers have migrated before killing migration_thread |
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On Thu, May 20, 2010 at 09:28:03AM +0200, Peter Zijlstra wrote: > On Wed, 2010-05-19 at 17:43 +0530, Amit K. Arora wrote: > > Alternate Solution considered : Another option considered was to > > increase the priority of the hrtimer cpu offline notifier, such that it > > gets to run before scheduler's migration cpu offline notifier. In this > > way we are sure that the timers will get migrated before migration_call > > tries to kill migration_thread. But, this can have some non-obvious > > implications, suggested Srivatsa. > > > > On Wed, May 19, 2010 at 11:31:55AM +0200, Peter Zijlstra wrote: > > > The other problem is more urgent though, CPU_POST_DEAD runs outside of > > > the hotplug lock and thus the above becomes a race where we could > > > possible kill off the migration thread of a newly brought up cpu: > > > > > > cpu0 - down 2 > > > cpu1 - up 2 (allocs a new migration thread, and leaks the old one) > > > cpu0 - post_down 2 - frees the migration thread -- oops! > > > > Ok. So, how about adding a check in CPU_UP_PREPARE event handling too ? > > The cpuset_lock will synchronize, and thus avoid race between killing of > > migration_thread in up_prepare and post_dead events. > > > > Here is the updated patch. If you don't like this one too, do you mind > > suggesting an alternate approach to tackle the problem ? Thanks ! > > Right, so this isn't pretty at all.. > > Ingo, the comment near the migration_notifier says that migration_call > should happen before all else, but can you see anything that would break > if we let the timer migration happen first? > > Thomas?
Hello Ingo, Thomas,
Do you see any potential problems with migrating the timers before the migration_call ?
Thanks! -- Regards, Amit Arora
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