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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2020C433F5 for ; Tue, 26 Apr 2022 17:19:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231587AbiDZRWv (ORCPT ); Tue, 26 Apr 2022 13:22:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230450AbiDZRWo (ORCPT ); Tue, 26 Apr 2022 13:22:44 -0400 Received: from out01.mta.xmission.com (out01.mta.xmission.com [166.70.13.231]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCD7D44753; Tue, 26 Apr 2022 10:19:34 -0700 (PDT) Received: from in01.mta.xmission.com ([166.70.13.51]:49348) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1njOqb-00AeV8-5Z; Tue, 26 Apr 2022 11:19:33 -0600 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:35722 helo=email.froward.int.ebiederm.org.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1njOqa-002Nau-7s; Tue, 26 Apr 2022 11:19:32 -0600 From: "Eric W. Biederman" To: Oleg Nesterov Cc: Peter Zijlstra , rjw@rjwysocki.net, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, bigeasy@linutronix.de, Will Deacon , linux-kernel@vger.kernel.org, tj@kernel.org, linux-pm@vger.kernel.org In-Reply-To: <20220426055122.GA29684@redhat.com> (Oleg Nesterov's message of "Tue, 26 Apr 2022 07:51:23 +0200") References: <20220421150248.667412396@infradead.org> <20220421150654.817117821@infradead.org> <20220425143537.GA12412@redhat.com> <20220425183343.GM2731@worktop.programming.kicks-ass.net> <87pml4llvm.fsf@email.froward.int.ebiederm.org> <20220426055122.GA29684@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) Date: Tue, 26 Apr 2022 12:19:20 -0500 Message-ID: <878rrrkbjb.fsf@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1njOqa-002Nau-7s;;;mid=<878rrrkbjb.fsf@email.froward.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=softfail X-XM-AID: U2FsdGVkX1+mtzpiqhlhzhmU0iIbDnQQBdvVxBQ/W88= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v2 2/5] sched,ptrace: Fix ptrace_check_attach() vs PREEMPT_RT X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov writes: > On 04/25, Eric W. Biederman wrote: >> >> I don't see JOBCTL_TRACED_QUIESCE being cleared "if (!current->ptrace)". > > As Peter explained, in this case we can rely on __ptrace_unlink() which > should clear this flag. I had missed that that signal_wake_up_state was clearing JOBCTL_TRACED_QUIESCE. Relying on __ptrace_unlink assumes the __ptrace_unlink happens after siglock is taken before calling ptrace_stop. Especially with the ptrace_notify in signal_delivered that does not look guaranteed. The __ptrace_unlink could also happen during arch_ptrace_stop. Relying on siglock is sufficient because __ptrace_unlink holds siglock over clearing task->ptrace. Which means that the simple fix for this is to just test task->ptrace before we set JOBCTL_TRACED_QUEIESCE. Eric