On Sun, Nov 27, 2011 at 11:30:01AM -0800, Tejun Heo wrote: > Hello, Frederic. > > On Fri, Nov 25, 2011 at 03:01:39PM +0100, Frederic Weisbecker wrote: > > > + /* > > > + * @tsk's threadgroup is going through changes - lock out users > > > + * which expect stable threadgroup. Do this before actually > > > + * starting tearing down @tsk so that locked threadgroup has either > > > + * alive or dead tasks, not something inbetween. > > > + */ > > > + threadgroup_change_begin(tsk); > > > + > > > > I still wonder why there is a so big coverage of this lock. I mean > > why is it called right before exit_irq_thread() and released so late. > > All we want is to lock cgroup_exit() I think, after which tasks can't be > > migrated. > > That way, cgroup plugins never see tasks in the process of > deconstruction. Its ->mm, ->sighand, ->signal and so on either don't > exist or continue to exist across all cgroup callbacks. It's simpler > and safer (especially as bugs in this area would only be visible when > migration and exit race), and if we're gonna synchronize exit path at > all, there isn't anything to lose by excluding the whole thing. Fine. But I don't think it's very useful to protect against irq_exit_thread(), what happens there is purely of internal irq interest. Then right after, PF_EXITING is set before any interesting change. Isn't it possible to simply lock this flag setting? IIRC, as soon as the PF_EXITING flag is set, you ignore the task for attachment. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
