freezer: Do not freeze tasks killed by OOM killer
authorCong Wang <xiyou.wangcong@gmail.com>
Tue, 21 Oct 2014 07:27:12 +0000 (09:27 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 14 Nov 2014 16:47:58 +0000 (08:47 -0800)
commitf95ad6ed20948dee0a7c1472250b530136f75db3
treef9183751531d9d0850fb925347d50012f39f7962
parent6ce75ebb5334c12febaf520682926ce34c3cfe2b
freezer: Do not freeze tasks killed by OOM killer

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/freezer.c