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Date:   Thu, 28 Apr 2022 16:57:50 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        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 <will@kernel.org>, tj@kernel.org,
        linux-pm@vger.kernel.org, Richard Weinberger <richard@nod.at>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        linux-um@lists.infradead.org, Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        inux-xtensa@linux-xtensa.org, Kees Cook <keescook@chromium.org>,
        Jann Horn <jannh@google.com>
Subject: Re: [PATCH 7/9] ptrace: Simplify the wait_task_inactive call in
 ptrace_check_attach
Message-ID: <20220428145750.GA15485@redhat.com>
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On 04/28, Peter Zijlstra wrote:
>
> On Thu, Apr 28, 2022 at 01:19:11PM +0200, Oleg Nesterov wrote:
> > > That is also the reason I couldn't do wait_task_inactive(task, 0)
> >
> > Ah, I din't notice this patch uses wait_task_inactive(child, 0),
> > I think it should do wait_task_inactive(child, __TASK_TRACED).
>
> Shouldn't we then switch wait_task_inactive() so have & matching instead
> of the current ==.

Sorry, I don't understand the context...

As long as ptrace_freeze_traced() sets __state == __TASK_TRACED (as it
currently does) wait_task_inactive(__TASK_TRACED) is what we need ?

After we change it to use JOBCTL_DELAY_WAKEKILL and not abuse __state,
ptrace_attach() should use wait_task_inactive(TASK_TRACED), but this
depends on what exactly we are going to do...

Oleg.