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From:   Waiman Long <llong@redhat.com>
Subject: Re: [PATCH v2] lockdep: Let lock_is_held_type() detect recursive read
 as read
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Waiman Long <llong@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>
References: <20210901162255.u2vhecaxgjsjfdtc@linutronix.de>
 <9af2b074-9fcf-5aea-f37d-9b2482146489@redhat.com>
 <20210903084001.lblecrvz4esl4mrr@linutronix.de>
Message-ID: <6bfddae4-dd66-b105-480f-ad4fe5c03276@redhat.com>
Date:   Wed, 8 Sep 2021 10:35:46 -0400
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On 9/3/21 4:40 AM, 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@linutronix.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)
>   				return LOCK_STATE_HELD;
>   
>   			return LOCK_STATE_NOT_HELD;
>
Thanks for accepting my suggestion.

Acked-by: Waiman Long <longman@redhat.com>