Messages in this thread | | | Subject | Re: [PATCH 07/10] mm, oom: fortify task_will_free_mem | From | Tetsuo Handa <> | Date | Thu, 9 Jun 2016 22:18:28 +0900 |
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Michal Hocko wrote: > @@ -766,15 +797,12 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, > * 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 > */ > - task_lock(p); > - if (p->mm && task_will_free_mem(p)) { > + if (task_will_free_mem(p)) {
I think it is possible that p->mm becomes NULL here.
Also, I think setting TIF_MEMDIE on p when find_lock_task_mm(p) != p is wrong. While oom_reap_task() will anyway clear TIF_MEMDIE even if we set TIF_MEMDIE on p when p->mm == NULL, it is not true for CONFIG_MMU=n case.
> mark_oom_victim(p); > - try_oom_reaper(p); > - task_unlock(p); > + wake_oom_reaper(p); > put_task_struct(p); > return; > } > - task_unlock(p); > > if (__ratelimit(&oom_rs)) > dump_header(oc, p); > @@ -940,14 +968,10 @@ bool out_of_memory(struct oom_control *oc) > * If current has a pending SIGKILL or is exiting, then automatically > * select it. The goal is to allow it to allocate so that it may > * quickly exit and free its memory. > - * > - * But don't select if current has already released its mm and cleared > - * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur. > */ > - if (current->mm && > - (fatal_signal_pending(current) || task_will_free_mem(current))) { > + if (task_will_free_mem(current)) {
Setting TIF_MEMDIE on current when current->mm == NULL and find_lock_task_mm(current) != NULL is wrong.
> mark_oom_victim(current); > - try_oom_reaper(current); > + wake_oom_reaper(current); > return true; > }
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