linux-kernel - Re: [PATCH 0/12] ptrace: cleaning up ptrace

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Date:   Mon, 2 May 2022 15:38:40 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, rjw@...ysocki.net, oleg@...hat.com,
        mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        Will Deacon <will@...nel.org>, tj@...nel.org,
        linux-pm@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org, Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>, linux-ia64@...r.kernel.org,
        tglx@...utronix.de
Subject: Re: [PATCH 0/12] ptrace: cleaning up ptrace_stop

On 2022-04-29 16:46:59 [-0500], Eric W. Biederman wrote:
> 
> The states TASK_STOPPED and TASK_TRACE are special in they can not
> handle spurious wake-ups.  This plus actively depending upon and
> changing the value of tsk->__state causes problems for PREEMPT_RT and
> Peter's freezer rewrite.

PREEMPT_RT wise, I had to duct tape wait_task_inactive() and remove the
preempt-disable section in ptrace_stop() (like previously). This reduces
the amount of __state + saved_state checks and looks otherwise stable in
light testing.

Sebastian