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    SubjectRe: [PATCH 1/6] proc, oom: drop bogus task_lock and mm check
    On Mon, May 30, 2016 at 03:05:51PM +0200, Michal Hocko wrote:
    > From: Michal Hocko <mhocko@suse.com>
    >
    > both oom_adj_write and oom_score_adj_write are using task_lock,
    > check for task->mm and fail if it is NULL. This is not needed because
    > the oom_score_adj is per signal struct so we do not need mm at all.
    > The code has been introduced by 3d5992d2ac7d ("oom: add per-mm oom
    > disable count") but we do not do per-mm oom disable since c9f01245b6a7
    > ("oom: remove oom_disable_count").
    >
    > The task->mm check is even not correct because the current thread might
    > have exited but the thread group might be still alive - e.g. thread
    > group leader would lead that echo $VAL > /proc/pid/oom_score_adj would
    > always fail with EINVAL while /proc/pid/task/$other_tid/oom_score_adj
    > would succeed. This is unexpected at best.
    >
    > Remove the lock along with the check to fix the unexpected behavior
    > and also because there is not real need for the lock in the first place.
    >
    > Signed-off-by: Michal Hocko <mhocko@suse.com>

    Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>

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