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SubjectRe: [PATCH] Fix race between oom kill and task exit
On 11/28, Ma, Xindong wrote:
>
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -412,16 +412,6 @@ 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);
>
> @@ -437,6 +427,16 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
> * still freeing memory.
> */
> read_lock(&tasklist_lock);
> + /*
> + * 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);
> + read_unlock(&tasklist_lock);
> + return;
> + }

I got lost... didn't we recently discussed the similar patch from Sameer?

This one doesn't look right. find_lock_task_mm() after unlock(tasklist)
can hit the same problem.

I belive the patch from Sameer was correct.

Oleg.



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