linux-kernel - Re: [PATCH v2 1/4] sched/task: Add the put_task_struct_atomic

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Message-ID: <20230217200437.551ad7c2@nowhere>
Date:   Fri, 17 Feb 2023 20:04:37 +0100
From:   luca abeni <luca.abeni@...tannapisa.it>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     Wander Lairson Costa <wander@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Stafford Horne <shorne@...il.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Andrei Vagin <avagin@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        Paul McKenney <paulmck@...nel.org>
Subject: Re: [PATCH v2 1/4] sched/task: Add the put_task_struct_atomic_safe
 function

Hi all,

On Fri, 17 Feb 2023 14:35:22 -0300
Daniel Bristot de Oliveira <bristot@...hat.com> wrote:

> On 1/30/23 08:49, Wander Lairson Costa wrote:
> >> Another thing, if you look at release_task_stack(), it either
> >> caches the outgoing stack for later use, or frees it via RCU
> >> (regardless of PREEMPT_RT). Perhaps we could follow that and just
> >> always punt the freeing of the task struct to RCU?
> >>  
> > That's a point. Do you mean doing that even for !PREEMPT_RT?
> >   
> 
> It seems that Luca Abeni (in Cc) is hitting the bug in the non-rt
> kernel with SCHED_DEADLINE...
> 
> adding him to the thread.

Thanks Daniel for adding me.

I triggered this "BUG: Invalid wait context" with a 5.15.76 kernel,
without PREEMPT_RT. I can reproduce it easily on a KVM-based VM; if
more information or tests are needed, let me know.


			Luca