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Date:   Tue, 5 Apr 2022 10:34:45 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Mel Gorman <mgorman@suse.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH v2] ptrace: fix ptrace vs tasklist_lock race on
 PREEMPT_RT.
Message-ID: <20220405083445.GA31401@redhat.com>
References: <Yh/b19JikC+Vnm8i@linutronix.de>
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 <20220315142944.GA22670@redhat.com>
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 <20220404161339.GA21531@redhat.com>
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On 04/04, Oleg Nesterov wrote:
>
> Cough. Somehow I can hardly understand v2. For example, if we fix
> wait_task_inactive() correctly, then why ptrace_freeze_traced()
> should take saved_state into account? And how can unfreeze_traced
> hit saved_state == __TASK_TRACED ?

OK, somehow I forgot that ptrace_freeze_traced() is called before
wait_task_inactive(), so it does need to check/change saved_state.

But still, ptrace_unfreeze_traced() can't see task->saved_state ==
__TASK_TRACED, right ?


Oleg.