From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1njj6D-001t4y-PP for linux-um@lists.infradead.org; Wed, 27 Apr 2022 14:57:03 +0000 Date: Wed, 27 Apr 2022 16:56:47 +0200 From: Oleg Nesterov Subject: Re: [PATCH 6/9] signal: Always call do_notify_parent_cldstop with siglock held Message-ID: <20220427145646.GC17421@redhat.com> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-6-ebiederm@xmission.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220426225211.308418-6-ebiederm@xmission.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, 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 , tj@kernel.org, linux-pm@vger.kernel.org, Peter Zijlstra , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , inux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn On 04/26, Eric W. Biederman wrote: > > @@ -2209,6 +2213,34 @@ static int ptrace_stop(int exit_code, int why, int clear_code, > spin_lock_irq(¤t->sighand->siglock); > } > > + /* Don't stop if current is not ptraced */ > + if (unlikely(!current->ptrace)) > + return (clear_code) ? 0 : exit_code; > + > + /* > + * If @why is CLD_STOPPED, we're trapping to participate in a group > + * stop. Do the bookkeeping. Note that if SIGCONT was delievered > + * across siglock relocks since INTERRUPT was scheduled, PENDING > + * could be clear now. We act as if SIGCONT is received after > + * TASK_TRACED is entered - ignore it. > + */ > + if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING)) > + gstop_done = task_participate_group_stop(current); > + > + /* > + * Notify parents of the stop. > + * > + * While ptraced, there are two parents - the ptracer and > + * the real_parent of the group_leader. The ptracer should > + * know about every stop while the real parent is only > + * interested in the completion of group stop. The states > + * for the two don't interact with each other. Notify > + * separately unless they're gonna be duplicates. > + */ > + do_notify_parent_cldstop(current, true, why); > + if (gstop_done && ptrace_reparented(current)) > + do_notify_parent_cldstop(current, false, why); This doesn't look right too. The parent should be notified only after we set __state = TASK_TRACED and ->exit code. Suppose that debugger sleeps in do_wait(). do_notify_parent_cldstop() wakes it up, debugger calls wait_task_stopped() and then it will sleep again, task_stopped_code() returns 0. This can be probably fixed if you remove the lockless (fast path) task_stopped_code() check in wait_task_stopped(), but this is not nice performance-wise... Oleg. _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um