From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id AFE716B0248 for ; Thu, 8 Jul 2010 06:49:45 -0400 (EDT) Subject: Re: FYI: mmap_sem OOM patch From: Peter Zijlstra In-Reply-To: References: <20100707231134.GA26555@google.com> <1278585009.1900.31.camel@laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Date: Thu, 08 Jul 2010 12:49:33 +0200 Message-ID: <1278586173.1900.50.camel@laptop> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org To: Michel Lespinasse Cc: linux-mm , KOSAKI Motohiro , LKML , Divyesh Shah , Ingo Molnar List-ID: On Thu, 2010-07-08 at 03:39 -0700, Michel Lespinasse wrote: >=20 >=20 > One way to fix this is to have T4 wake from the oom queue and ret= urn an > allocation failure instead of insisting on going oom itself when = T1 > decides to take down the task. >=20 > How would you have T4 figure out the deadlock situation ? T1 is taking do= wn T2, not T4...=20 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. -- 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