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    Subject[PATCH 3.12 135/206] freezer: Do not freeze tasks killed by OOM killer
    Date
    From: Cong Wang <xiyou.wangcong@gmail.com>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    commit 51fae6da640edf9d266c94f36bc806c63c301991 upstream.

    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)
    Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
    Signed-off-by: Michal Hocko <mhocko@suse.cz>
    Acked-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    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;

    --
    2.1.3


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