Messages in this thread | | | Date | Sun, 28 Mar 2010 18:28:21 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH] oom killer: break from infinite loop |
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On 03/28, anfei wrote: > > On Fri, Mar 26, 2010 at 11:33:56PM +0100, Oleg Nesterov wrote: > > > Off-topic, but we shouldn't use force_sig(), SIGKILL doesn't > > need "force" semantics. > > > This may need a dedicated patch, there are some other places to > force_sig(SIGKILL, ...) too.
Yes, yes, sure.
> > I'd wish I could understand the changelog ;) > > > Assume thread A and B are in the same group. If A runs into the oom, > and selects B as the victim, B won't exit because at least in exit_mm(), > it can not get the mm->mmap_sem semaphore which A has already got.
I see. But still I can't understand. To me, the problem is not that B can't exit, the problem is that A doesn't know it should exit. All threads should exit and free ->mm. Even if B could exit, this is not enough. And, to some extent, it doesn't matter if it holds mmap_sem or not.
Don't get me wrong. Even if I don't understand oom_kill.c the patch looks obviously good to me, even from "common sense" pov. I am just curious.
So, my understanding is: we are going to kill the whole thread group but TIF_MEMDIE is per-thread. Mark the whole thread group as TIF_MEMDIE so that any thread can notice this flag and (say, __alloc_pages_slowpath) fail asap.
Is my understanding correct?
Oleg.
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