locking/static_key: Don't take sleeping locks in __static_key_slow_de…

…c_deferred()

Changing jump_label state is protected by jump_label_lock().
Rate limited static_key_slow_dec(), however, will never
directly call jump_label_update(), it will schedule a delayed
work instead.  Therefore it's unnecessary to take both the
cpus_read_lock() and jump_label_lock().

This allows static_key_slow_dec_deferred() to be called
from atomic contexts, like socket destructing in net/tls,
without the need for another indirection.

Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

kernel/jump_label.c

@@ -221,63 +221,57 @@ static bool static_key_slow_try_dec(struct static_key *key)
 	return true;
 }
 
-static void __static_key_slow_dec_cpuslocked(struct static_key *key,
-					   unsigned long rate_limit,
-					   struct delayed_work *work)
+static void __static_key_slow_dec_cpuslocked(struct static_key *key)
 {
 	lockdep_assert_cpus_held();
 
 	if (static_key_slow_try_dec(key))
 		return;
 
 	jump_label_lock();
-	if (atomic_dec_and_test(&key->enabled)) {
-		if (rate_limit) {
-			atomic_inc(&key->enabled);
-			schedule_delayed_work(work, rate_limit);
-		} else {
-			jump_label_update(key);
-		}
-	}
+	if (atomic_dec_and_test(&key->enabled))
+		jump_label_update(key);
 	jump_label_unlock();
 }
 
-static void __static_key_slow_dec(struct static_key *key,
-				  unsigned long rate_limit,
-				  struct delayed_work *work)
+static void __static_key_slow_dec(struct static_key *key)
 {
 	cpus_read_lock();
-	__static_key_slow_dec_cpuslocked(key, rate_limit, work);
+	__static_key_slow_dec_cpuslocked(key);
 	cpus_read_unlock();
 }
 
 void jump_label_update_timeout(struct work_struct *work)
 {
 	struct static_key_deferred *key =
 		container_of(work, struct static_key_deferred, work.work);
-	__static_key_slow_dec(&key->key, 0, NULL);
+	__static_key_slow_dec(&key->key);
 }
 EXPORT_SYMBOL_GPL(jump_label_update_timeout);
 
 void static_key_slow_dec(struct static_key *key)
 {
 	STATIC_KEY_CHECK_USE(key);
-	__static_key_slow_dec(key, 0, NULL);
+	__static_key_slow_dec(key);
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec);
 
 void static_key_slow_dec_cpuslocked(struct static_key *key)
 {
 	STATIC_KEY_CHECK_USE(key);
-	__static_key_slow_dec_cpuslocked(key, 0, NULL);
+	__static_key_slow_dec_cpuslocked(key);
 }
 
 void __static_key_slow_dec_deferred(struct static_key *key,
 				    struct delayed_work *work,
 				    unsigned long timeout)
 {
 	STATIC_KEY_CHECK_USE(key);
-	__static_key_slow_dec(key, timeout, work);
+
+	if (static_key_slow_try_dec(key))
+		return;
+
+	schedule_delayed_work(work, timeout);
 }
 EXPORT_SYMBOL_GPL(__static_key_slow_dec_deferred);