linux-kernel - [PATCH v2 13/24] locking/lockdep: Stop using RCU primitives to access all_lock

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Message-Id: <20181204002833.55452-14-bvanassche@acm.org>
Date:   Mon,  3 Dec 2018 16:28:22 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     mingo@...hat.com
Cc:     peterz@...radead.org, tj@...nel.org, longman@...hat.com,
        johannes.berg@...el.com, linux-kernel@...r.kernel.org,
        Bart Van Assche <bvanassche@....org>,
        Johannes Berg <johannes@...solutions.net>
Subject: [PATCH v2 13/24] locking/lockdep: Stop using RCU primitives to access all_lock_classes

Due to the previous patch all code that accesses the 'all_lock_classes'
list holds the graph lock. Hence use regular list primitives instead of
their RCU variants to access this list.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Waiman Long <longman@...hat.com>
Cc: Johannes Berg <johannes@...solutions.net>
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
 kernel/locking/lockdep.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e78623819184..5c837a537273 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -629,7 +629,8 @@ static int static_obj(void *obj)
 
 /*
  * To make lock name printouts unique, we calculate a unique
- * class->name_version generation counter:
+ * class->name_version generation counter. The caller must hold the graph
+ * lock.
  */
 static int count_matching_names(struct lock_class *new_class)
 {
@@ -639,7 +640,7 @@ static int count_matching_names(struct lock_class *new_class)
 	if (!new_class->name)
 		return 0;
 
-	list_for_each_entry_rcu(class, &all_lock_classes, lock_entry) {
+	list_for_each_entry(class, &all_lock_classes, lock_entry) {
 		if (new_class->key - new_class->subclass == class->key)
 			return class->name_version;
 		if (class->name && !strcmp(class->name, new_class->name))
@@ -803,7 +804,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 	/*
 	 * Add it to the global list of classes:
 	 */
-	list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
+	list_add_tail(&class->lock_entry, &all_lock_classes);
 
 	if (verbose(class)) {
 		graph_unlock();
@@ -4122,6 +4123,9 @@ void lockdep_reset(void)
 	raw_local_irq_restore(flags);
 }
 
+/*
+ * Remove all references to a lock class. The caller must hold the graph lock.
+ */
 static void zap_class(struct lock_class *class)
 {
 	int i;
@@ -4138,7 +4142,7 @@ static void zap_class(struct lock_class *class)
 	 * Unhash the class and remove it from the all_lock_classes list:
 	 */
 	hlist_del_rcu(&class->hash_entry);
-	list_del_rcu(&class->lock_entry);
+	list_del(&class->lock_entry);
 
 	RCU_INIT_POINTER(class->key, NULL);
 	RCU_INIT_POINTER(class->name, NULL);
-- 
2.20.0.rc1.387.gf8505762e3-goog