linux-kernel - Re: [RESEND x3][PATCH v12 2/7] locking/mutex: Make mutex::wait

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANDhNCof4=mP9NBonXK9vSvxwbMN6gF9xUxqWgsVAE=Kj+F90w@mail.gmail.com>
Date: Thu, 10 Oct 2024 19:26:24 -0700
From: John Stultz <jstultz@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Joel Fernandes <joelaf@...gle.com>, Qais Yousef <qyousef@...alina.io>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Valentin Schneider <vschneid@...hat.com>, 
	Ben Segall <bsegall@...gle.com>, Zimuzo Ezeozue <zezeozue@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Metin Kaya <Metin.Kaya@....com>, 
	Xuewen Yan <xuewen.yan94@...il.com>, K Prateek Nayak <kprateek.nayak@....com>, 
	Thomas Gleixner <tglx@...utronix.de>, Daniel Lezcano <daniel.lezcano@...aro.org>, kernel-team@...roid.com, 
	"Connor O'Brien" <connoro@...gle.com>
Subject: Re: [RESEND x3][PATCH v12 2/7] locking/mutex: Make mutex::wait_lock
 irq safe

On Thu, Oct 10, 2024 at 7:00 AM Steven Rostedt <rostedt@...dmis.org> wrote:
> On Wed,  9 Oct 2024 16:53:35 -0700
> John Stultz <jstultz@...gle.com> wrote:
>
> > From: Juri Lelli <juri.lelli@...hat.com>
> >
> > mutex::wait_lock might be nested under rq->lock.
> >
> > Make it irq safe then.
>
> Can you expand on this please?
>
> If the mutex:wait_lock might be taken under an rq->lock, doesn't that mean
> a mutex was taken under rq->lock? Or is it something internal?
>
> This change log needs to be more explicit.

Sure! Would the following work for you?

"With the proxy-execution series, we traverse the task->mutex->task
blocked_on/owner chain in the scheduler core. We do this while holding
the rq::lock to keep the structures in place while taking and
releasing the alternating lock types.

Since the mutex::wait_lock is one of the locks we will take in this
way under the rq::lock in the scheduler core, we need to make sure
that its usage elsewhere is irq safe."

?

Thanks for the feedback!
-john