Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754788Ab0FHLmM (ORCPT ); Tue, 8 Jun 2010 07:42:12 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:43608 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754590Ab0FHLl6 (ORCPT ); Tue, 8 Jun 2010 07:41:58 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: "Luis Claudio R. Goncalves" , LKML , linux-mm , Oleg Nesterov , David Rientjes , Andrew Morton , KAMEZAWA Hiroyuki , Nick Piggin Subject: Re: [PATCH 12/12] oom: give current access to memory reserves if it has been killed Cc: kosaki.motohiro@jp.fujitsu.com In-Reply-To: <20100603152653.726B.A69D9226@jp.fujitsu.com> References: <20100603135106.7247.A69D9226@jp.fujitsu.com> <20100603152653.726B.A69D9226@jp.fujitsu.com> Message-Id: <20100607083650.8736.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 8 Jun 2010 20:41:51 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2390 Lines: 58 > From: David Rientjes > > It's possible to livelock the page allocator if a thread has > mm->mmap_sem and fails to make forward progress because the > oom killer selects another thread sharing the same ->mm to > kill that cannot exit until the semaphore is dropped. > > The oom killer will not kill multiple tasks at the same time; each oom > killed task must exit before another task may be killed. Thus, if one > thread is holding mm->mmap_sem and cannot allocate memory, all threads > sharing the same ->mm are blocked from exiting as well. In the oom kill > case, that means the thread holding mm->mmap_sem will never free > additional memory since it cannot get access to memory reserves and the > thread that depends on it with access to memory reserves cannot exit > because it cannot acquire the semaphore. Thus, the page allocators > livelocks. > > When the oom killer is called and current happens to have a pending > SIGKILL, this patch automatically gives it access to memory reserves and > returns. Upon returning to the page allocator, its allocation will > hopefully succeed so it can quickly exit and free its memory. If not, > the page allocator will fail the allocation if it is not __GFP_NOFAIL. > > Reviewed-by: KAMEZAWA Hiroyuki > Signed-off-by: David Rientjes > Signed-off-by: KOSAKI Motohiro > --- > mm/oom_kill.c | 10 ++++++++++ > 1 files changed, 10 insertions(+), 0 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 67b5fa5..ad85e1b 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -638,6 +638,16 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, > } > > /* > + * If current has a pending SIGKILL, then automatically select it. The > + * goal is to allow it to allocate so that it may quickly exit and free > + * its memory. > + */ > + if (fatal_signal_pending(current)) { > + set_tsk_thread_flag(current, TIF_MEMDIE); > + return; > + } Self NAK this. We have no gurantee that current is oom killable. Oh, here is out_of_memory(), sigh. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/