Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Yuyang Du <duyuyang@gmail.com>
To:     peterz@infradead.org, will.deacon@arm.com, mingo@kernel.org
Cc:     bvanassche@acm.org, ming.lei@redhat.com, frederic@kernel.org,
        tglx@linutronix.de, linux-kernel@vger.kernel.org,
        Yuyang Du <duyuyang@gmail.com>
Subject: [PATCH 24/28] locking/lockdep: Remove !dir in lock irq usage check
Date:   Wed, 24 Apr 2019 18:19:30 +0800
Message-Id: <20190424101934.51535-25-duyuyang@gmail.com>
In-Reply-To: <20190424101934.51535-1-duyuyang@gmail.com>
References: <20190424101934.51535-1-duyuyang@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In mark_lock_irq(), the following checks are performed:

   ----------------------------------
  |   ->      | unsafe | read unsafe |
  |----------------------------------|
  | safe      |  F  B  |    F* B*    |
  |----------------------------------|
  | read safe |  F? B* |      -      |
   ----------------------------------

Where:
F: check_usage_forwards
B: check_usage_backwards
*: check enabled by STRICT_READ_CHECKS
?: check enabled by the !dir condition

From checking point of view, the special F? case does not make sense,
whereas it perhaps is made for peroformance concern. As later patch will
address this issue, remove this exception, which makes the checks
consistent later.

With STRICT_READ_CHECKS = 1 which is default, there is no functional
change.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
---
 kernel/locking/lockdep.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1b78216..2f24028 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3149,7 +3149,7 @@ typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
 	 * Validate that the lock dependencies don't have conflicting usage
 	 * states.
 	 */
-	if ((!read || !dir || STRICT_READ_CHECKS) &&
+	if ((!read || STRICT_READ_CHECKS) &&
 			!usage(curr, this, excl_bit, state_name(new_bit & ~LOCK_USAGE_READ_MASK)))
 		return 0;
 
-- 
1.8.3.1