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@acm.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: shenghui <shhuiw@foxmail.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@kernel.org>

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e16766f..e221be7 100644 (file)
--- 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. */