1 files changed, 32 insertions, 36 deletions

diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index b077b1b2d4b3..03cb97a8e4cd 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -901,7 +901,7 @@ done:
  */
 static inline void clear_nonspinnable(struct rw_semaphore *sem)
 {
-	if (rwsem_test_oflags(sem, RWSEM_NONSPINNABLE))
+	if (unlikely(rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)))
 		atomic_long_andnot(RWSEM_NONSPINNABLE, &sem->owner);
 }
 
@@ -926,6 +926,31 @@ rwsem_spin_on_owner(struct rw_semaphore *sem)
 #endif
 
 /*
+ * Prepare to wake up waiter(s) in the wait queue by putting them into the
+ * given wake_q if the rwsem lock owner isn't a writer. If rwsem is likely
+ * reader-owned, wake up read lock waiters in queue front or wake up any
+ * front waiter otherwise.
+
+ * This is being called from both reader and writer slow paths.
+ */
+static inline void rwsem_cond_wake_waiter(struct rw_semaphore *sem, long count,
+					  struct wake_q_head *wake_q)
+{
+	enum rwsem_wake_type wake_type;
+
+	if (count & RWSEM_WRITER_MASK)
+		return;
+
+	if (count & RWSEM_READER_MASK) {
+		wake_type = RWSEM_WAKE_READERS;
+	} else {
+		wake_type = RWSEM_WAKE_ANY;
+		clear_nonspinnable(sem);
+	}
+	rwsem_mark_wake(sem, wake_type, wake_q);
+}
+
+/*
  * Wait for the read lock to be granted
  */
 static struct rw_semaphore __sched *
@@ -935,7 +960,6 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat
 	long rcnt = (count >> RWSEM_READER_SHIFT);
 	struct rwsem_waiter waiter;
 	DEFINE_WAKE_Q(wake_q);
-	bool wake = false;
 
 	/*
 	 * To prevent a constant stream of readers from starving a sleeping
@@ -996,22 +1020,11 @@ queue:
 	/* we're now waiting on the lock, but no longer actively locking */
 	count = atomic_long_add_return(adjustment, &sem->count);
 
-	/*
-	 * If there are no active locks, wake the front queued process(es).
-	 *
-	 * If there are no writers and we are first in the queue,
-	 * wake our own waiter to join the existing active readers !
-	 */
-	if (!(count & RWSEM_LOCK_MASK)) {
-		clear_nonspinnable(sem);
-		wake = true;
-	}
-	if (wake || (!(count & RWSEM_WRITER_MASK) &&
-		    (adjustment & RWSEM_FLAG_WAITERS)))
-		rwsem_mark_wake(sem, RWSEM_WAKE_ANY, &wake_q);
-
+	rwsem_cond_wake_waiter(sem, count, &wake_q);
 	raw_spin_unlock_irq(&sem->wait_lock);
-	wake_up_q(&wake_q);
+
+	if (!wake_q_empty(&wake_q))
+		wake_up_q(&wake_q);
 
 	/* wait to be given the lock */
 	for (;;) {
@@ -1050,7 +1063,6 @@ out_nolock:
 static struct rw_semaphore __sched *
 rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 {
-	long count;
 	struct rwsem_waiter waiter;
 	DEFINE_WAKE_Q(wake_q);
 
@@ -1074,23 +1086,8 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 
 	/* we're now waiting on the lock */
 	if (rwsem_first_waiter(sem) != &waiter) {
-		count = atomic_long_read(&sem->count);
-
-		/*
-		 * If there were already threads queued before us and:
-		 *  1) there are no active locks, wake the front
-		 *     queued process(es) as the handoff bit might be set.
-		 *  2) there are no active writers and some readers, the lock
-		 *     must be read owned; so we try to wake any read lock
-		 *     waiters that were queued ahead of us.
-		 */
-		if (count & RWSEM_WRITER_MASK)
-			goto wait;
-
-		rwsem_mark_wake(sem, (count & RWSEM_READER_MASK)
-					? RWSEM_WAKE_READERS
-					: RWSEM_WAKE_ANY, &wake_q);
-
+		rwsem_cond_wake_waiter(sem, atomic_long_read(&sem->count),
+				       &wake_q);
 		if (!wake_q_empty(&wake_q)) {
 			/*
 			 * We want to minimize wait_lock hold time especially
@@ -1105,7 +1102,6 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 		atomic_long_or(RWSEM_FLAG_WAITERS, &sem->count);
 	}
 
-wait:
 	/* wait until we successfully acquire the lock */
 	set_current_state(state);
 	for (;;) {