linux-kernel - [tip:locking/core] locking/lockdep: Remove !dir in lock irq usage check

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Date:   Mon, 3 Jun 2019 06:22:24 -0700
From:   tip-bot for Yuyang Du <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        duyuyang@...il.com, tglx@...utronix.de, mingo@...nel.org,
        hpa@...or.com, torvalds@...ux-foundation.org
Subject: [tip:locking/core] locking/lockdep: Remove !dir in lock irq usage
 check

Commit-ID:  bf998b98f5bce4ebc97b3980016f54fabb7a4958
Gitweb:     https://git.kernel.org/tip/bf998b98f5bce4ebc97b3980016f54fabb7a4958
Author:     Yuyang Du <duyuyang@...il.com>
AuthorDate: Mon, 6 May 2019 16:19:39 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 3 Jun 2019 11:55:53 +0200

locking/lockdep: Remove !dir in lock irq usage check

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@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: bvanassche@....org
Cc: frederic@...nel.org
Cc: ming.lei@...hat.com
Cc: will.deacon@....com
Link: https://lkml.kernel.org/r/20190506081939.74287-24-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 9c4e2a7547d3..2168e94715b9 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3235,7 +3235,7 @@ mark_lock_irq(struct task_struct *curr, struct held_lock *this,
 	 * 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;