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freezer: Do not freeze tasks killed by OOM killer
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Since f660daa (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 a320122 (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 f660daa.

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: a320122 (freezer: make freezing() test freeze conditions in effect instead of TIF_FREEZE)
Cc: 3.3+ <stable@vger.kernel.org> # 3.3+
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>
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Cong Wang authored and Rafael J. Wysocki committed Oct 21, 2014
1 parent f114040 commit 51fae6d
Showing 1 changed file with 3 additions and 0 deletions.
3 changes: 3 additions & 0 deletions kernel/freezer.c
Original file line number Diff line number Diff line change
@@ -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;

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