From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 96E5E6B0248 for ; Thu, 8 Jul 2010 06:57:44 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o68AvgC0025459 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Thu, 8 Jul 2010 19:57:42 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 2F50F45DE6E for ; Thu, 8 Jul 2010 19:57:42 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id F0B8645DE6F for ; Thu, 8 Jul 2010 19:57:41 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id DCCB91DB803B for ; Thu, 8 Jul 2010 19:57:41 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.249.87.106]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 9ADE61DB8037 for ; Thu, 8 Jul 2010 19:57:41 +0900 (JST) From: KOSAKI Motohiro Subject: Re: FYI: mmap_sem OOM patch In-Reply-To: <1278586173.1900.50.camel@laptop> References: <1278586173.1900.50.camel@laptop> Message-Id: <20100708195421.CD48.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Date: Thu, 8 Jul 2010 19:57:40 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Peter Zijlstra Cc: kosaki.motohiro@jp.fujitsu.com, Michel Lespinasse , linux-mm , LKML , Divyesh Shah , Ingo Molnar List-ID: > On Thu, 2010-07-08 at 03:39 -0700, Michel Lespinasse wrote: > > > > > > One way to fix this is to have T4 wake from the oom queue and return an > > allocation failure instead of insisting on going oom itself when T1 > > decides to take down the task. > > > > How would you have T4 figure out the deadlock situation ? T1 is taking down T2, not T4... > > If T2 and T4 share a mmap_sem they belong to the same process. OOM takes > down the whole process by sending around signals of sorts (SIGKILL?), so > if T4 gets a fatal signal while it is waiting to enter the oom thingy, > have it abort and return an allocation failure. > > That alloc failure (along with a pending fatal signal) will very likely > lead to the release of its mmap_sem (if not, there's more things to > cure). > > At which point the cycle is broken an stuff continues as it was > intended. Now, I've reread current code. I think mmotm already have this. T4 call out_of_memory and get TIF_MEMDIE ========================================================= void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order, nodemask_t *nodemask) { (snip) /* * 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_thread_flag(TIF_MEMDIE); boost_dying_task_prio(current, NULL); return; } ================================================================== alloc_pages immediately return if the task have TIF_MEMDIE ================================================================== static inline struct page * __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, struct zonelist *zonelist, enum zone_type high_zoneidx, nodemask_t *nodemask, struct zone *preferred_zone, int migratetype) { (snip) /* Avoid allocations with no watermarks from looping endlessly */ if (test_thread_flag(TIF_MEMDIE) && !(gfp_mask & __GFP_NOFAIL)) goto nopage; ========================================================================== Thought? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org