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linux-next/include/linux/sched
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Tetsuo Handa 9bcdeb51bd oom, oom_reaper: do not enqueue same task twice 
Arkadiusz reported that enabling memcg's group oom killing causes
strange memcg statistics where there is no task in a memcg despite the
number of tasks in that memcg is not 0.  It turned out that there is a
bug in wake_oom_reaper() which allows enqueuing same task twice which
makes impossible to decrease the number of tasks in that memcg due to a
refcount leak.

This bug existed since the OOM reaper became invokable from
task_will_free_mem(current) path in out_of_memory() in Linux 4.7,

  T1@P1     |T2@P1     |T3@P1     |OOM reaper
  ----------+----------+----------+------------
                                   # Processing an OOM victim in a different memcg domain.
                        try_charge()
                          mem_cgroup_out_of_memory()
                            mutex_lock(&oom_lock)
             try_charge()
               mem_cgroup_out_of_memory()
                 mutex_lock(&oom_lock)
  try_charge()
    mem_cgroup_out_of_memory()
      mutex_lock(&oom_lock)
                            out_of_memory()
                              oom_kill_process(P1)
                                do_send_sig_info(SIGKILL, @P1)
                                mark_oom_victim(T1@P1)
                                wake_oom_reaper(T1@P1) # T1@P1 is enqueued.
                            mutex_unlock(&oom_lock)
                 out_of_memory()
                   mark_oom_victim(T2@P1)
                   wake_oom_reaper(T2@P1) # T2@P1 is enqueued.
                 mutex_unlock(&oom_lock)
      out_of_memory()
        mark_oom_victim(T1@P1)
        wake_oom_reaper(T1@P1) # T1@P1 is enqueued again due to oom_reaper_list == T2@P1 && T1@P1->oom_reaper_list == NULL.
      mutex_unlock(&oom_lock)
                                   # Completed processing an OOM victim in a different memcg domain.
                                   spin_lock(&oom_reaper_lock)
                                   # T1P1 is dequeued.
                                   spin_unlock(&oom_reaper_lock)

but memcg's group oom killing made it easier to trigger this bug by
calling wake_oom_reaper() on the same task from one out_of_memory()
request.

Fix this bug using an approach used by commit 855b018325 ("oom,
oom_reaper: disable oom_reaper for oom_kill_allocating_task").  As a
side effect of this patch, this patch also avoids enqueuing multiple
threads sharing memory via task_will_free_mem(current) path.

Link: http://lkml.kernel.org/r/e865a044-2c10-9858-f4ef-254bc71d6cc2@i-love.sakura.ne.jp
Link: http://lkml.kernel.org/r/5ee34fc6-1485-34f8-8790-903ddabaa809@i-love.sakura.ne.jp
Fixes: af8e15cc85 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Arkadiusz Miskiewicz <arekm@maven.pl>
Tested-by: Arkadiusz Miskiewicz <arekm@maven.pl>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Aleksa Sarai <asarai@suse.de>
Cc: Jay Kamat <jgkamat@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-02-01 15:46:23 -08:00
..
autogroup.h
clock.h
coredump.h oom, oom_reaper: do not enqueue same task twice 2019-02-01 15:46:23 -08:00
cpufreq.h sched/cpufreq: Prepare schedutil for Energy Aware Scheduling 2018-12-11 15:16:58 +01:00
cputime.h
deadline.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
debug.h
hotplug.h
idle.h
init.h
isolation.h sched: Fix various typos in comments 2018-12-03 11:55:42 +01:00
jobctl.h
loadavg.h sched: loadavg: make calc_load_n() public 2018-10-26 16:26:32 -07:00
mm.h sched: Fix various typos in comments 2018-12-03 11:55:42 +01:00
nohz.h sched/nohz: Clean up nohz enter/exit 2018-03-09 07:59:19 +01:00
numa_balancing.h
prio.h
rt.h
signal.h signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
smt.h x86/speculation: Rework SMT state change 2018-11-28 11:57:07 +01:00
stat.h sched: Fix various typos in comments 2018-12-03 11:55:42 +01:00
sysctl.h kernel/hung_task.c: allow to set checking interval separately from timeout 2018-08-22 10:52:47 -07:00
task_stack.h
task.h fork: fix some -Wmissing-prototypes warnings 2019-01-04 13:13:47 -08:00
topology.h sched/topology: Relocate arch_scale_cpu_capacity() to the internal header 2018-12-11 15:16:58 +01:00
user.h userns: use refcount_t for reference counting instead atomic_t 2018-08-22 10:52:46 -07:00
wake_q.h sched/wake_q: Document wake_q_add() 2019-01-21 11:15:36 +01:00
xacct.h