linux-kernel - Re: [PATCH v2 01/34] compiler_types: Move lock checking attributes to compiler-capability-analysis.h

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Message-ID: <b6af185f-0109-4f98-a2d7-ab8f716e21a5@stanley.mountain>
Date: Wed, 5 Mar 2025 12:27:04 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Marco Elver <elver@...gle.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Arnd Bergmann <arnd@...db.de>, Bart Van Assche <bvanassche@....org>,
	Bill Wendling <morbo@...gle.com>, Boqun Feng <boqun.feng@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
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	Jonathan Corbet <corbet@....net>,
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	linux-crypto@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 01/34] compiler_types: Move lock checking attributes
 to compiler-capability-analysis.h

On Wed, Mar 05, 2025 at 10:13:44AM +0100, Marco Elver wrote:
> On Wed, Mar 05, 2025 at 11:36AM +0300, Dan Carpenter wrote:
> > On Tue, Mar 04, 2025 at 10:21:00AM +0100, Marco Elver wrote:
> > > +#ifndef _LINUX_COMPILER_CAPABILITY_ANALYSIS_H
> > > +#define _LINUX_COMPILER_CAPABILITY_ANALYSIS_H
> > > +
> > > +#ifdef __CHECKER__
> > > +
> > > +/* Sparse context/lock checking support. */
> > > +# define __must_hold(x)		__attribute__((context(x,1,1)))
> > > +# define __acquires(x)		__attribute__((context(x,0,1)))
> > > +# define __cond_acquires(x)	__attribute__((context(x,0,-1)))
> > > +# define __releases(x)		__attribute__((context(x,1,0)))
> > > +# define __acquire(x)		__context__(x,1)
> > > +# define __release(x)		__context__(x,-1)
> > > +# define __cond_lock(x, c)	((c) ? ({ __acquire(x); 1; }) : 0)
> > > +
> > 
> > The other thing you might want to annotate is ww_mutex_destroy().
> 
> We can add an annotation to check the lock is not held:
> 

Sorry, my email was bad.

I haven't actually tried your patch at all.  I have locking check in
Smatch so I'm just basing this on the things that I did...
https://github.com/error27/smatch/blob/master/smatch_locking.c
This isn't a mandatory thing.  Whatever happens we're going to end up
doing dozens of patches all over the kernel later.

I thought you could destroy a mutex regardless or whether it was held
or not.  I was getting false positives which said that we should drop
the lock on error but actually the mutex is destroyed on that path so it
doesn't matter.

regards,
dan carpenter