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SubjectRe: [PATCH 1/4] freezer: Do not freeze tasks killed by OOM killer
Date
On Tuesday, October 21, 2014 09:27:12 AM Michal Hocko wrote:
> From: Cong Wang <xiyou.wangcong@gmail.com>
>
> Since f660daac474c6f (oom: thaw threads if oom killed thread is frozen
> before deferring) OOM killer relies on being able to thaw a frozen task
> to handle OOM situation but a3201227f803 (freezer: make freezing() test
> freeze conditions in effect instead of TIF_FREEZE) has reorganized the
> code and stopped clearing freeze flag in __thaw_task. This means that
> the target task only wakes up and goes into the fridge again because the
> freezing condition hasn't changed for it. This reintroduces the bug
> fixed by f660daac474c6f.
>
> Fix the issue by checking for TIF_MEMDIE thread flag in
> freezing_slow_path and exclude the task from freezing completely. If a
> task was already frozen it would get woken by __thaw_task from OOM killer
> and get out of freezer after rechecking freezing().
>
> Changes since v1
> - put TIF_MEMDIE check into freezing_slowpath rather than in __refrigerator
> as per Oleg
> - return __thaw_task into oom_scan_process_thread because
> oom_kill_process will not wake task in the fridge because it is
> sleeping uninterruptible
>
> [mhocko@suse.cz: rewrote the changelog]
> Fixes: a3201227f803 (freezer: make freezing() test freeze conditions in effect instead of TIF_FREEZE)
> Cc: stable@vger.kernel.org # 3.3+
> Cc: David Rientjes <rientjes@google.com>
> Cc: Michal Hocko <mhocko@suse.cz>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
> Acked-by: Oleg Nesterov <oleg@redhat.com>

ACK

> ---
> kernel/freezer.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/freezer.c b/kernel/freezer.c
> index aa6a8aadb911..8f9279b9c6d7 100644
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -42,6 +42,9 @@ bool freezing_slow_path(struct task_struct *p)
> if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK))
> return false;
>
> + if (test_thread_flag(TIF_MEMDIE))
> + return false;
> +
> if (pm_nosig_freezing || cgroup_freezing(p))
> return true;
>
>

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.


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