On Monday, September 08, 2014 04:29:24 PM Cong Wang 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?
There's no way to do that currently as PM freezing is all-inclusive. > Interesting, but I am not familiar with PM. I'm wondering if the OOM killer might avoid killing frozen tasks instead? Or there might be a "suspend" operation for the OOM killer that would be run from a PM notifier to guaratee that the OOM killer would not mess up with things during the entire system suspend (which surely is not quite useful anyway). -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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/
