On Wed 10-09-14 13:30:25, Cong Wang wrote: > On Mon, Sep 8, 2014 at 4:29 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote: > > On Mon, Sep 8, 2014 at 4:42 PM, Rafael J. Wysocki <r...@rjwysocki.net> > > wrote: > >> On Monday, September 08, 2014 04:16:15 PM Cong Wang wrote: > >>> On Mon, Sep 8, 2014 at 4:23 PM, Rafael J. Wysocki <r...@rjwysocki.net> > >>> wrote: > >>> > > >>> > The reason why it matters for the suspend-time freezing is that we > >>> > freeze tasks > >>> > to take them out of the picture entirely until they are thawed. > >>> > Therefore we > >>> > can't allow them to go back to the picture just for a while until they > >>> > are > >>> > killed. Frozen tasks are not supposed to get back to the picture at > >>> > all. > >>> > > >>> > >>> > >>> Ok, then checking TIF_MEMDIE is unsafe for PM freeze, we should > >>> keep the cgroup_freezing() test to make sure freeze request is from > >>> cgroup not PM. Question got answered. :) > >> > >> Do I think correctly that cgroups freezing and system suspend are > >> mutually exclusive? If not, then this still is problematic. > > > > Good point! Although rare, but it is possible we freeze a process both from > > cgroup and PM. Hmm, this means we have to explicitly exclude PM rather > > just checking cgroup freeze? Interesting, but I am not familiar with PM. > > > > I am wondering if the folllowing check makes any sense with regarding > to rule out PM freeze: > > if ((!pm_nosig_freezing && !pm_freezing) && > cgroup_freezing(current) && test_thread_flag(TIF_MEMDIE)) > return true;
Why is this needed in the first place? What if OOM happens in the middle of task freezing during freeze_processes? Also killing a task at that stage should be safe as no devices are suspended yet and OOM killer is disabled after all tasks are frozen and allocations fail at that stage. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
