From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 28 Apr 2022 12:42:07 +0200 From: Peter Zijlstra Subject: Re: [PATCH 7/9] ptrace: Simplify the wait_task_inactive call in ptrace_check_attach Message-ID: References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-7-ebiederm@xmission.com> <20220427151455.GE17421@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220427151455.GE17421@redhat.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: Oleg Nesterov Cc: "Eric W. Biederman" , 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, 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 Wed, Apr 27, 2022 at 05:14:57PM +0200, Oleg Nesterov wrote: > On 04/26, Eric W. Biederman wrote: > > > > Asking wait_task_inactive to verify that tsk->__state == __TASK_TRACED > > was needed to detect the when ptrace_stop would decide not to stop > > after calling "set_special_state(TASK_TRACED)". With the recent > > cleanups ptrace_stop will always stop after calling set_special_state. > > > > Take advatnage of this by no longer asking wait_task_inactive to > > verify the state. If a bug is hit and wait_task_inactive does not > > succeed warn and return -ESRCH. > > ACK, but I think that the changelog is wrong. > > We could do this right after may_ptrace_stop() has gone. This doesn't > depend on the previous changes in this series. It very much does rely on there not being any blocking between set_special_state() and schedule() tho. So all those PREEMPT_RT spinlock->rt_mutex things need to be gone. That is also the reason I couldn't do wait_task_inactive(task, 0) in the other patch, I had to really match 'TASK_TRACED or TASK_FROZEN' any other state must fail (specifically TASK_RTLOCK_WAIT must not match). _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um