linux-kernel - Re: [PATCH 1/2] lockdep: add lockdep_assert_not

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Message-ID: <eb819e72fb2d897e603654d44aeda8c6f337453f.camel@sipsolutions.net>
Date:   Mon, 15 Feb 2021 17:10:14 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Shuah Khan <skhan@...uxfoundation.org>, mingo@...hat.com,
        will@...nel.org, kvalo@...eaurora.org, davem@...emloft.net,
        kuba@...nel.org, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()

On Mon, 2021-02-15 at 17:04 +0100, Peter Zijlstra wrote:
> On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote:
> > On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote:
> > > I think something like so will work, but please double check.
> > 
> > Yeah, that looks better.
> > 
> > > +++ b/include/linux/lockdep.h
> > > @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
> > >  
> > >  #define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
> > >  
> > > -#define lockdep_assert_held(l)	do {				\
> > > -		WARN_ON(debug_locks && !lockdep_is_held(l));	\
> > > +#define lockdep_assert_held(l)	do {					\
> > > +		WARN_ON(debug_locks && lockdep_is_held(l) == 0));	\
> > >  	} while (0)
> > 
> > That doesn't really need to change? It's the same.
> 
> Correct, but I found it more symmetric vs the not implementation below.

Fair enough. One might argue that you should have an

enum lockdep_lock_state {
	LOCK_STATE_NOT_HELD, /* 0 now */
	LOCK_STATE_HELD, /* 1 now */
	LOCK_STATE_UNKNOWN, /* -1 with your patch but might as well be 2 */
};

:)

johannes