linux-kernel - Re: [PATCH v2] lockdep: Let lock_is_held_type() detect recursive read as read

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Date:   Wed, 8 Sep 2021 10:16:19 +0800
From:   Boqun Feng <boqun.feng@...il.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Waiman Long <llong@...hat.com>, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] lockdep: Let lock_is_held_type() detect recursive
 read as read

On Fri, Sep 03, 2021 at 10:40:01AM +0200, Sebastian Andrzej Siewior wrote:
> lock_is_held_type(, 1) detects acquired read locks. It only recognized
> locks acquired with lock_acquire_shared(). Read locks acquired with
> lock_acquire_shared_recursive() are not recognized because a `2' is
> stored as the read value.
> 
> Rework the check to additionally recognise lock's read value one and two
> as a read held lock.
> 
> Fixes: e918188611f07 ("locking: More accurate annotations for read_lock()")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
> v1…v2:
>   - simplify the read check to !!read as suggested by Waiman Long.
> 
>  kernel/locking/lockdep.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -5366,7 +5366,7 @@ int __lock_is_held(const struct lockdep_
>  		struct held_lock *hlock = curr->held_locks + i;
>  
>  		if (match_held_lock(hlock, lock)) {
> -			if (read == -1 || hlock->read == read)
> +			if (read == -1 || hlock->read == !!read)

I think this should be:

	!!hlock->read == read

With that,

Acked-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

>  				return LOCK_STATE_HELD;
>  
>  			return LOCK_STATE_NOT_HELD;