linux-kernel - Re: [PATCH] locking/mutex: Disable preemption in __mutex_unlock

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CAHk-=wjT5Y36Xs1zdE1OdM-AwxUMcC9fQC=8r1_GvawP1oqC3Q@mail.gmail.com>
Date: Wed, 9 Jul 2025 11:28:54 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Waiman Long <longman@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Jonathan Corbet <corbet@....net>, 
	linux-kernel@...r.kernel.org, Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH] locking/mutex: Disable preemption in __mutex_unlock_slowpath()

On Wed, 9 Jul 2025 at 11:21, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> And I suspect it would involve the exact *opposite* of your patch:
> make mutex_unlock() actively cause preemption after it has released
> the lock but before it has done the final accesses.

.. sadly, I suspect we have a ton of mutex_unlock() users in atomic
contexts, so we probably can't do that. It's not like you *should* do
it, but I don't think we've ever disallowed it.

You can't use mutex_unlock from interrupts etc, but you can use it
while holding a spinlock.

           Linus