Re: [PATCH] mm/oom: Suppress unnecessary "sharing same memory" message.

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Michal Hocko wrote:
> On Mon 01-06-15 19:51:05, Tetsuo Handa wrote:
> [...]
> > How can all fatal_signal_pending() "struct task_struct" get access to memory
> > reserves when only one of fatal_signal_pending() "struct task_struct" has
> > TIF_MEMDIE ?
> 
> Because of 
> 	/*
> 	 * 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))) {
> 		mark_oom_victim(current);
> 		goto out;
> 	}

Then, what guarantees that the thread which is between
down_write(&current->mm->mmap_sem) and up_write(&current->mm->mmap_sem)
(or whatever locks which are blocking the OOM victim) calls out_of_memory() ?
That thread might be doing !__GFP_FS allocation request.

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