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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 582B6C28CC0 for ; Thu, 30 May 2019 10:35:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B4A725762 for ; Thu, 30 May 2019 10:35:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726761AbfE3Kfn (ORCPT ); Thu, 30 May 2019 06:35:43 -0400 Received: from foss.arm.com ([217.140.101.70]:33934 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725870AbfE3Kfm (ORCPT ); Thu, 30 May 2019 06:35:42 -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 153F2374; Thu, 30 May 2019 03:35:42 -0700 (PDT) Received: from lakrids.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 429CB3F5AF; Thu, 30 May 2019 03:35:39 -0700 (PDT) Date: Thu, 30 May 2019 11:35:36 +0100 From: Mark Rutland To: Peter Zijlstra Cc: Will Deacon , Young Xiao <92siuyang@gmail.com>, linux@armlinux.org.uk, 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: <20190530103536.GA56046@lakrids.cambridge.arm.com> References: <20190529101042.GN2623@hirez.programming.kicks-ass.net> <20190529102022.GC4485@fuggles.cambridge.arm.com> <20190529125557.GU2623@hirez.programming.kicks-ass.net> <20190529130521.GA11023@fuggles.cambridge.arm.com> <20190529132515.GW2623@hirez.programming.kicks-ass.net> <20190529143510.GA11154@fuggles.cambridge.arm.com> <20190529161955.GZ2623@hirez.programming.kicks-ass.net> <20190529162435.GM31777@lakrids.cambridge.arm.com> <20190529163854.GN31777@lakrids.cambridge.arm.com> <20190529170313.GE2623@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190529170313.GE2623@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) 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 07:03:13PM +0200, Peter Zijlstra wrote: > On Wed, May 29, 2019 at 05:38:54PM +0100, Mark Rutland wrote: > > Generally speaking though, if we ever task task_pt_regs() of an idle > > task we'll get junk, and user_mode() could be true. > > Agreed, but we're not doing that. Sure. I just think that might be an argument for having task_pt_regs() return NULL for kthreads, or having a WARN_ON_ONCE(t->flags & PF_KTHREAD) to catch missing checks elsewhere. Thanks, Mark. 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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 07:03:13PM +0200, Peter Zijlstra wrote: > On Wed, May 29, 2019 at 05:38:54PM +0100, Mark Rutland wrote: > > Generally speaking though, if we ever task task_pt_regs() of an idle > > task we'll get junk, and user_mode() could be true. > > Agreed, but we're not doing that. Sure. I just think that might be an argument for having task_pt_regs() return NULL for kthreads, or having a WARN_ON_ONCE(t->flags & PF_KTHREAD) to catch missing checks elsewhere. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel