linux-kernel - Re: [PATCH] devcoredump: Fix circular locking dependency with devcd->mutex.

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Message-ID: <247568f47e1955be454e951e80a9063123f97c66.camel@sipsolutions.net>
Date: Fri, 24 Oct 2025 10:39:39 +0200
From: Johannes Berg <johannes@...solutions.net>
To: Maarten Lankhorst <dev@...khorst.se>, linux-kernel@...r.kernel.org
Cc: intel-xe@...ts.freedesktop.org, Mukesh Ojha <quic_mojha@...cinc.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Danilo Krummrich	 <dakr@...nel.org>,
 stable@...r.kernel.org, Matthew Brost <matthew.brost@...el.com>
Subject: Re: [PATCH] devcoredump: Fix circular locking dependency with
 devcd->mutex.

On Fri, 2025-10-24 at 10:37 +0200, Maarten Lankhorst wrote:
> > 
> > CPU 0				CPU 1
> > 
> > dev_coredump_put()		devcd_del()
> >  -> devcd_free()
> >    -> locked
> >      -> !deleted
> >      -> __devcd_del()
> > 				-> __devcd_del()
> > 
> > no?
> > 
> > johannes
> 
> 
> Yeah don't you love the races in the design? All intricate and subtle.

:)

> In this case it's handled by disable_delayed_work_sync(),
> which waits for devcd_del() to be completed. devcd_del is called from the workqueue,
> and the first step devcd_free does is calling disable_delayed_work_sync, which means
> devcd_del() either fully completed or was not run at all.

Oh... right, I totally missed the _sync. My bad, sorry.

I guess I really should say

Reviewed-by: Johannes Berg <johannes@...solutions.net>

since I finally _did_ review it carefully. Sorry it took forever.

johannes