[CCing Andrew]
On Sun 24-01-16 00:47:20, Tetsuo Handa wrote:
> While oom_killer_disable() is called by freeze_processes() after all user
> threads except the current thread are frozen, it is possible that kernel
> threads invoke the OOM killer and sends SIGKILL to the current thread due
> to sharing the thawed victim's memory. Therefore, checking for SIGKILL is
> preferable than TIF_MEMDIE.
This alone wouldn't cause any issue wrt. oom_killer_disable expected
behavior ATM because the only user of this functionality is the PM
freezer itself and that is a sync context so it cannot unexpectedly
race with the suspend progress but it is true that this check is more
robust. Even though this is _really_ unlikely because the suspend
usually doesn't share the mm with a large task it doesn't make any sense
to continue with the suspend if the trigger itself has been killed by
the OOM killer so this is a minor improvement.
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/oom_kill.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 6ebc0351..914451a 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -613,15 +613,11 @@ void exit_oom_victim(struct task_struct *tsk)
> bool oom_killer_disable(void)
> {
> /*
> - * Make sure to not race with an ongoing OOM killer
> - * and that the current is not the victim.
> + * Make sure to not race with an ongoing OOM killer. Check that the
> + * current is not killed (possibly due to sharing the victim's memory).
> */
> - mutex_lock(&oom_lock);
> - if (test_thread_flag(TIF_MEMDIE)) {
> - mutex_unlock(&oom_lock);
> + if (mutex_lock_killable(&oom_lock))
> return false;
> - }
> -
> oom_killer_disabled = true;
> mutex_unlock(&oom_lock);
>
> --
> 1.8.3.1
>
> --
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--
Michal Hocko
SUSE Labs
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