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 1nlYGg-001all-Fz for linux-um@lists.infradead.org; Mon, 02 May 2022 15:47:26 +0000 Date: Mon, 2 May 2022 17:47:08 +0200 From: Oleg Nesterov Subject: Re: [PATCH v2 07/12] ptrace: Don't change __state Message-ID: <20220502154708.GE17276@redhat.com> References: <87k0b7v9yk.fsf_-_@email.froward.int.ebiederm.org> <20220429214837.386518-7-ebiederm@xmission.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220429214837.386518-7-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 , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org On 04/29, Eric W. Biederman wrote: > > static void ptrace_unfreeze_traced(struct task_struct *task) > { > - if (READ_ONCE(task->__state) != __TASK_TRACED) > - return; > - > - WARN_ON(!task->ptrace || task->parent != current); > + unsigned long flags; > > /* > - * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up remotely. > - * Recheck state under the lock to close this race. > + * The child may be awake and may have cleared > + * JOBCTL_PTRACE_FROZEN (see ptrace_resume). The child will > + * not set JOBCTL_PTRACE_FROZEN or enter __TASK_TRACED anew. > */ > - spin_lock_irq(&task->sighand->siglock); > - if (READ_ONCE(task->__state) == __TASK_TRACED) { > + if (lock_task_sighand(task, &flags)) { > + task->jobctl &= ~JOBCTL_PTRACE_FROZEN; Well, I think that the fast-path if (!(task->jobctl & JOBCTL_PTRACE_FROZEN)) return; at the start makes sense, we can avoid lock_task_sighand() if the tracee was resumed. Oleg. _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um