From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BCBDC28CC0 for ; Wed, 29 May 2019 13:05:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E947320673 for ; Wed, 29 May 2019 13:05:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727033AbfE2NFa (ORCPT ); Wed, 29 May 2019 09:05:30 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:45626 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726613AbfE2NF3 (ORCPT ); Wed, 29 May 2019 09:05:29 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4389080D; Wed, 29 May 2019 06:05:29 -0700 (PDT) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 71F863F59C; Wed, 29 May 2019 06:05:26 -0700 (PDT) Date: Wed, 29 May 2019 14:05:21 +0100 From: Will Deacon To: Peter Zijlstra Cc: Young Xiao <92siuyang@gmail.com>, linux@armlinux.org.uk, mark.rutland@arm.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, kan.liang@linux.intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ravi.bangoria@linux.vnet.ibm.com, mpe@ellerman.id.au, acme@redhat.com, eranian@google.com, fweisbec@gmail.com, jolsa@redhat.com Subject: Re: [PATCH] perf: Fix oops when kthread execs user process Message-ID: <20190529130521.GA11023@fuggles.cambridge.arm.com> References: <1559046689-24091-1-git-send-email-92siuyang@gmail.com> <20190528140103.GT2623@hirez.programming.kicks-ass.net> <20190528153224.GE20758@fuggles.cambridge.arm.com> <20190528173228.GW2623@hirez.programming.kicks-ass.net> <20190529091733.GA4485@fuggles.cambridge.arm.com> <20190529101042.GN2623@hirez.programming.kicks-ass.net> <20190529102022.GC4485@fuggles.cambridge.arm.com> <20190529125557.GU2623@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190529125557.GU2623@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 29, 2019 at 02:55:57PM +0200, Peter Zijlstra wrote: > On Wed, May 29, 2019 at 11:20:22AM +0100, Will Deacon wrote: > > Anyway, you can add my ack to your patch, but I bet we can remove that mm > > check :D > > I've ended up with the below. Ravi, can you test if that does indeed > obsolete your PPC patch? > > --- > Subject: perf: Fix perf_sample_regs_user() > From: Peter Zijlstra > Date: Wed May 29 14:37:24 CEST 2019 > > perf_sample_regs_user() uses 'current->mm' to test for the presence of > userspace, but this is insufficient, consider use_mm(). > > A better test is: '!(current->flags & PF_KTHREAD)', exec() clears > PF_KTHREAD after it sets the new ->mm but before it drops to userspace > for the first time. > > Possibly obsoletes: bf05fc25f268 ("powerpc/perf: Fix oops when kthread execs user process") > > Reported-by: Ravi Bangoria > Reported-by: Young Xiao <92siuyang@gmail.com> > Cc: Ravi Bangoria > Cc: Naveen N. Rao > Cc: Michael Ellerman > Cc: Jiri Olsa > Cc: Frederic Weisbecker > Cc: Stephane Eranian > Cc: Arnaldo Carvalho de Melo > Acked-by: Will Deacon > Fixes: 4018994f3d87 ("perf: Add ability to attach user level registers dump to sample") > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/events/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -5923,7 +5923,7 @@ static void perf_sample_regs_user(struct > if (user_mode(regs)) { Hmm, so it just occurred to me that Mark's observation is that the regs can be junk in some cases. In which case, should we be checking for kthreads first? Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CE53C28CC0 for ; Wed, 29 May 2019 13:05:42 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E435F20673 for ; Wed, 29 May 2019 13:05:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="DCHcQboP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E435F20673 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9YgOUbINi0ELljsVu4qgcUYDAa9nty1JeumxQ58P++8=; b=DCHcQboPFgtBXw 7vOE21gWOV+2j+a5OqtRvrco5/HwHCIMOWbz3jkkZcY4/ZEQV4y1cbD+PsjE0wokxT7uJdJRwiBv1 4t43dMDROkhmWZSF/YAORCqmxc7nIdcT6+SAzmHWRSDt/5yQwJiDs/DpGDefDX2JJ2qtv6EGI4gB9 Ug6Rl7+esuPWDkDZNJWa4HqbD2XAqTqBwjH9Zl5DAel3iF3gczxmC0/HXezoYA/4bJxnQZBLvz5FO CHtwoC++HrZm4ANDINgqzKQ7gun2oabAYMNyUEuzZg36VG5yVvco0LjiyacgKXkzJIK7idJtdb7tg s2BSh1QZFXQZfy57a8pQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hVyGq-0004Pj-Cc; Wed, 29 May 2019 13:05:32 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hVyGn-0004PN-Tj for linux-arm-kernel@lists.infradead.org; Wed, 29 May 2019 13:05:31 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4389080D; Wed, 29 May 2019 06:05:29 -0700 (PDT) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 71F863F59C; Wed, 29 May 2019 06:05:26 -0700 (PDT) Date: Wed, 29 May 2019 14:05:21 +0100 From: Will Deacon To: Peter Zijlstra Subject: Re: [PATCH] perf: Fix oops when kthread execs user process Message-ID: <20190529130521.GA11023@fuggles.cambridge.arm.com> References: <1559046689-24091-1-git-send-email-92siuyang@gmail.com> <20190528140103.GT2623@hirez.programming.kicks-ass.net> <20190528153224.GE20758@fuggles.cambridge.arm.com> <20190528173228.GW2623@hirez.programming.kicks-ass.net> <20190529091733.GA4485@fuggles.cambridge.arm.com> <20190529101042.GN2623@hirez.programming.kicks-ass.net> <20190529102022.GC4485@fuggles.cambridge.arm.com> <20190529125557.GU2623@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190529125557.GU2623@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190529_060529_966298_9B1F2E37 X-CRM114-Status: GOOD ( 18.25 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, Young Xiao <92siuyang@gmail.com>, mpe@ellerman.id.au, jolsa@redhat.com, x86@kernel.org, linux@armlinux.org.uk, eranian@google.com, linux-kernel@vger.kernel.org, acme@redhat.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, ravi.bangoria@linux.vnet.ibm.com, fweisbec@gmail.com, linux-arm-kernel@lists.infradead.org, kan.liang@linux.intel.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 29, 2019 at 02:55:57PM +0200, Peter Zijlstra wrote: > On Wed, May 29, 2019 at 11:20:22AM +0100, Will Deacon wrote: > > Anyway, you can add my ack to your patch, but I bet we can remove that mm > > check :D > > I've ended up with the below. Ravi, can you test if that does indeed > obsolete your PPC patch? > > --- > Subject: perf: Fix perf_sample_regs_user() > From: Peter Zijlstra > Date: Wed May 29 14:37:24 CEST 2019 > > perf_sample_regs_user() uses 'current->mm' to test for the presence of > userspace, but this is insufficient, consider use_mm(). > > A better test is: '!(current->flags & PF_KTHREAD)', exec() clears > PF_KTHREAD after it sets the new ->mm but before it drops to userspace > for the first time. > > Possibly obsoletes: bf05fc25f268 ("powerpc/perf: Fix oops when kthread execs user process") > > Reported-by: Ravi Bangoria > Reported-by: Young Xiao <92siuyang@gmail.com> > Cc: Ravi Bangoria > Cc: Naveen N. Rao > Cc: Michael Ellerman > Cc: Jiri Olsa > Cc: Frederic Weisbecker > Cc: Stephane Eranian > Cc: Arnaldo Carvalho de Melo > Acked-by: Will Deacon > Fixes: 4018994f3d87 ("perf: Add ability to attach user level registers dump to sample") > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/events/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -5923,7 +5923,7 @@ static void perf_sample_regs_user(struct > if (user_mode(regs)) { Hmm, so it just occurred to me that Mark's observation is that the regs can be junk in some cases. In which case, should we be checking for kthreads first? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel