From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 4C39B6B1FF2 for ; Tue, 21 Aug 2018 13:51:05 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id r41-v6so3161649edd.15 for ; Tue, 21 Aug 2018 10:51:05 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id g13-v6si1295502edf.328.2018.08.21.10.51.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Aug 2018 10:51:03 -0700 (PDT) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w7LHnXAM092879 for ; Tue, 21 Aug 2018 13:51:02 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2m0n7rx1e7-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 21 Aug 2018 13:51:01 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 21 Aug 2018 18:51:00 +0100 Date: Tue, 21 Aug 2018 10:50:49 -0700 From: Ram Pai Subject: Re: Odd SIGSEGV issue introduced by commit 6b31d5955cb29 ("mm, oom: fix potential data corruption when oom_reaper races with writer") Reply-To: Ram Pai References: <7767bdf4-a034-ecb9-1ac8-4fa87f335818@c-s.fr> <871sasmddc.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 In-Reply-To: <871sasmddc.fsf@concordia.ellerman.id.au> Message-Id: <20180821175049.GA5905@ram.oc3035372033.ibm.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Michael Ellerman Cc: Christophe LEROY , Michal Hocko , Andrew Morton , "linuxppc-dev@lists.ozlabs.org" , linux-mm On Tue, Aug 21, 2018 at 04:40:15PM +1000, Michael Ellerman wrote: > Christophe LEROY writes: > ... > > > > And I bisected its disappearance with commit 99cd1302327a2 ("powerpc: > > Deliver SEGV signal on pkey violation") > > Whoa that's weird. > > > Looking at those two commits, especially the one which makes it > > dissapear, I'm quite sceptic. Any idea on what could be the cause and/or > > how to investigate further ? > > Are you sure it's not some corruption that just happens to be masked by > that commit? I can't see anything in that commit that could explain that > change in behaviour. > > The only real change is if you're hitting DSISR_KEYFAULT isn't it? even with the 'commit 99cd1302327a2', a SEGV signal should get generated; which should kill the process. Unless the process handles SEGV signals with SEGV_PKUERR differently. The other surprising thing is, why is DSISR_KEYFAULT getting generated in the first place? Are keys somehow getting programmed into the HPTE? Feels like some random corruption. Is this behavior seen with power8 or power9? RP