Subject: Re: [PATCH] locking/mutex: Initialize mutex::magic even when LOCKDEP=n

From: Peter Zijlstra <[email-masked]>
Date: Fri, 28 Nov 2025 10:36:06 +0100

On Tue, Nov 25, 2025 at 06:54:21AM -0800, Boqun Feng wrote:
> When DEBUG_MUTEXES=y and LOCKDEP=n, mutex_lock() still checks on
> ->magic, hence debug_mutex_init() should be called in
> mutex_init_generic() as well. While we are at it, decouple LOCKDEP
> logic from debug_mutex_init(), because in this way debug_mutex_init()
> only needs one parameter, and we now have mutex_init_lockep() for
> LOCKDEP=y scenarios.
> 
> Reported-by: Stephen Rothwell <[email-masked]>
> Closes: https://lore.kernel.org/lkml/[email-masked]/
> Reported-by: Nathan Chancellor <[email-masked]>
> Closes: https://lore.kernel.org/lkml/20251121215819.GA1374726@ax162/
> Fixes: 3572e2edc7b6 ("locking/mutex: Redo __mutex_init()")
> Reviewed-by: Waiman Long <[email-masked]>
> Signed-off-by: Boqun Feng <[email-masked]>
> ---
> Peter,
> 
> Feel free to fold it into commit 3572e2edc7b6 ("locking/mutex: Redo
> __mutex_init()"), just resend it properly so it won't fall off your
> radar ;-)

Clearly I've been suffering too much mail again :/ Let me go frob stuff.