linux-kernel - Re: [PATCH 22/28] locking/lockdep: Adjust new bit cases in mark

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Message-ID: <20190425195212.GW12232@hirez.programming.kicks-ass.net>
Date:   Thu, 25 Apr 2019 21:52:12 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yuyang Du <duyuyang@...il.com>
Cc:     will.deacon@....com, mingo@...nel.org, bvanassche@....org,
        ming.lei@...hat.com, frederic@...nel.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/28] locking/lockdep: Adjust new bit cases in mark_lock

On Wed, Apr 24, 2019 at 06:19:28PM +0800, Yuyang Du wrote:
> The new bit can be any possible lock usage except it is garbage, so the

s/except it/except when it/ ?

> cases in switch can be made simpler. Warn early on if wrong usage bit is
> passed without taking locks. No functional change.
> 
> Signed-off-by: Yuyang Du <duyuyang@...il.com>
> ---
>  kernel/locking/lockdep.c | 21 +++++++--------------
>  1 file changed, 7 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index c08ec88..291cc9c 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3476,6 +3476,11 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
>  {
>  	unsigned int new_mask = 1 << new_bit, ret = 1;
>  
> +	if (new_bit >= LOCK_USAGE_STATES) {
> +		WARN_ON(1);

Does that want to be DEBUG_LOCKS_WARN_ON() ?

> +		return 0;
> +	}
> +
>  	/*
>  	 * If already set then do not dirty the cacheline,
>  	 * nor do any checks:
> @@ -3499,25 +3504,13 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
>  		return 0;
>  
>  	switch (new_bit) {
> -#define LOCKDEP_STATE(__STATE)			\
> -	case LOCK_USED_IN_##__STATE:		\
> -	case LOCK_USED_IN_##__STATE##_READ:	\
> -	case LOCK_ENABLED_##__STATE:		\
> -	case LOCK_ENABLED_##__STATE##_READ:
> -#include "lockdep_states.h"
> -#undef LOCKDEP_STATE
> -		ret = mark_lock_irq(curr, this, new_bit);
> -		if (!ret)
> -			return 0;
> -		break;
>  	case LOCK_USED:
>  		debug_atomic_dec(nr_unused_locks);
>  		break;
>  	default:
> -		if (!debug_locks_off_graph_unlock())
> +		ret = mark_lock_irq(curr, this, new_bit);
> +		if (!ret)
>  			return 0;
> -		WARN_ON(1);
> -		return 0;
>  	}
>  
>  	graph_unlock();
> -- 
> 1.8.3.1
>