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 will put the following as a comment: >> >> /* OOM killer may decide to kill this process after it is frozen, >> in this case SIGKILL can never be handled, so we should check >> TIF_MEMDIE and if it is set, thaw and let SIGKILL kill it. >> But for PM freeze, it is not allowed to get out even for a while, >> so we have to keep it being frozen. */ >> >> Let me know if it looks good to you. > > Well, it reflects the reality, so it's good enough. But please adhere to the > coding style rules for comments. > Sure thing. Thanks! -- 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/
