linux-kernel - [tip:locking/urgent] locking/lockdep: Make lockdep_unregister_key() honor 'debug

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Message-ID: <tip-8b39adbee805c539a461dbf208b125b096152b1c@git.kernel.org>
Date:   Tue, 16 Apr 2019 00:01:14 -0700
From:   tip-bot for Bart Van Assche <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, will.deacon@....com,
        bvanassche@....org, linux-kernel@...r.kernel.org,
        shhuiw@...mail.com, mingo@...nel.org, longman@...hat.com,
        peterz@...radead.org, tglx@...utronix.de, hpa@...or.com
Subject: [tip:locking/urgent] locking/lockdep: Make lockdep_unregister_key()
 honor 'debug_locks' again

Commit-ID:  8b39adbee805c539a461dbf208b125b096152b1c
Gitweb:     https://git.kernel.org/tip/8b39adbee805c539a461dbf208b125b096152b1c
Author:     Bart Van Assche <bvanassche@....org>
AuthorDate: Mon, 15 Apr 2019 10:05:38 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 16 Apr 2019 08:21:51 +0200

locking/lockdep: Make lockdep_unregister_key() honor 'debug_locks' again

If lockdep_register_key() and lockdep_unregister_key() are called with
debug_locks == false then the following warning is reported:

  WARNING: CPU: 2 PID: 15145 at kernel/locking/lockdep.c:4920 lockdep_unregister_key+0x1ad/0x240

That warning is reported because lockdep_unregister_key() ignores the
value of 'debug_locks' and because the behavior of lockdep_register_key()
depends on whether or not 'debug_locks' is set. Fix this inconsistency
by making lockdep_unregister_key() take 'debug_locks' again into
account.

Signed-off-by: Bart Van Assche <bvanassche@....org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Waiman Long <longman@...hat.com>
Cc: Will Deacon <will.deacon@....com>
Cc: shenghui <shhuiw@...mail.com>
Fixes: 90c1cba2b3b3 ("locking/lockdep: Zap lock classes even with lock debugging disabled")
Link: http://lkml.kernel.org/r/20190415170538.23491-1-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/locking/lockdep.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e16766ff184b..e221be724fe8 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4907,8 +4907,9 @@ void lockdep_unregister_key(struct lock_class_key *key)
 		return;
 
 	raw_local_irq_save(flags);
-	arch_spin_lock(&lockdep_lock);
-	current->lockdep_recursion = 1;
+	if (!graph_lock())
+		goto out_irq;
+
 	pf = get_pending_free();
 	hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
 		if (k == key) {
@@ -4920,8 +4921,8 @@ void lockdep_unregister_key(struct lock_class_key *key)
 	WARN_ON_ONCE(!found);
 	__lockdep_free_key_range(pf, key, 1);
 	call_rcu_zapped(pf);
-	current->lockdep_recursion = 0;
-	arch_spin_unlock(&lockdep_lock);
+	graph_unlock();
+out_irq:
 	raw_local_irq_restore(flags);
 
 	/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */