linux-kernel - Re: [PATCH] locking/refcount: add sparse annotations to dec-and-lock functions

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Message-ID: <20191228201518.GA266348@zzz.localdomain>
Date:   Sat, 28 Dec 2019 14:15:18 -0600
From:   Eric Biggers <ebiggers@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will@...nel.org>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] locking/refcount: add sparse annotations to dec-and-lock
 functions

On Sat, Dec 28, 2019 at 12:49:18PM +0100, Peter Zijlstra wrote:
> On Thu, Dec 26, 2019 at 09:29:22AM -0600, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> > 
> > Wrap refcount_dec_and_lock() and refcount_dec_and_lock_irqsave() with
> > macros using __cond_lock() so that 'sparse' doesn't report warnings
> > about unbalanced locking when using them.
> > 
> > This is the same thing that's done for their atomic_t equivalents.
> > 
> > Don't annotate refcount_dec_and_mutex_lock(), because mutexes don't
> > currently have sparse annotations.
> 
> I so f'ing hate that __cond_lock() crap. Previously I've suggested
> fixing sparse instead of making such an atrocious trainwreck of the
> code.

What is your suggestion exactly?  There has to be an annotation for this,
because by design sparse only analyzes individual translation units; it's not a
full-blown static analyzer that operates on the AST for the whole kernel.

- Eric