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    Subject[PATCH] OOM killer: wait for tasks with pending SIGKILL to exit
    Date
    If OOM killer finds a task which is about to exit or is already doing so,
    there is no need to kill anyone. It should just wait until task dies.

    Add missing fatal_signal_pending() check and allow selected task to use memory
    reserves in order to exit quickly.

    Also remove redundant PF_EXITING check after victim has been selected.

    Signed-off-by: Sergey Dyasly <dserrg@gmail.com>
    ---
    mm/oom_kill.c | 17 +++++------------
    1 file changed, 5 insertions(+), 12 deletions(-)

    diff --git a/mm/oom_kill.c b/mm/oom_kill.c
    index 98e75f2..ef83b81 100644
    --- a/mm/oom_kill.c
    +++ b/mm/oom_kill.c
    @@ -275,13 +275,16 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
    if (oom_task_origin(task))
    return OOM_SCAN_SELECT;

    - if (task->flags & PF_EXITING && !force_kill) {
    + if ((task->flags & PF_EXITING || fatal_signal_pending(task)) &&
    + !force_kill) {
    /*
    * If this task is not being ptraced on exit, then wait for it
    * to finish before killing some other task unnecessarily.
    */
    - if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
    + if (!(task->group_leader->ptrace & PT_TRACE_EXIT)) {
    + set_tsk_thread_flag(task, TIF_MEMDIE);
    return OOM_SCAN_ABORT;
    + }
    }
    return OOM_SCAN_OK;
    }
    @@ -412,16 +415,6 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
    static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
    DEFAULT_RATELIMIT_BURST);

    - /*
    - * If the task is already exiting, don't alarm the sysadmin or kill
    - * its children or threads, just set TIF_MEMDIE so it can die quickly
    - */
    - if (p->flags & PF_EXITING) {
    - set_tsk_thread_flag(p, TIF_MEMDIE);
    - put_task_struct(p);
    - return;
    - }
    -
    if (__ratelimit(&oom_rs))
    dump_header(p, gfp_mask, order, memcg, nodemask);

    --
    1.8.1.2


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