1 files changed, 14 insertions, 72 deletions

diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
index 2655f26ec882..c7471c3fb798 100644
--- a/kernel/locking/qrwlock.c
+++ b/kernel/locking/qrwlock.c
@@ -23,49 +23,11 @@
 #include <linux/spinlock.h>
 #include <asm/qrwlock.h>
 
-/*
- * This internal data structure is used for optimizing access to some of
- * the subfields within the atomic_t cnts.
- */
-struct __qrwlock {
-	union {
-		atomic_t cnts;
-		struct {
-#ifdef __LITTLE_ENDIAN
-			u8 wmode;	/* Writer mode   */
-			u8 rcnts[3];	/* Reader counts */
-#else
-			u8 rcnts[3];	/* Reader counts */
-			u8 wmode;	/* Writer mode   */
-#endif
-		};
-	};
-	arch_spinlock_t	lock;
-};
-
-/**
- * rspin_until_writer_unlock - inc reader count & spin until writer is gone
- * @lock  : Pointer to queue rwlock structure
- * @writer: Current queue rwlock writer status byte
- *
- * In interrupt context or at the head of the queue, the reader will just
- * increment the reader count & wait until the writer releases the lock.
- */
-static __always_inline void
-rspin_until_writer_unlock(struct qrwlock *lock, u32 cnts)
-{
-	while ((cnts & _QW_WMASK) == _QW_LOCKED) {
-		cpu_relax();
-		cnts = atomic_read_acquire(&lock->cnts);
-	}
-}
-
 /**
  * queued_read_lock_slowpath - acquire read lock of a queue rwlock
  * @lock: Pointer to queue rwlock structure
- * @cnts: Current qrwlock lock value
  */
-void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts)
+void queued_read_lock_slowpath(struct qrwlock *lock)
 {
 	/*
 	 * Readers come here when they cannot get the lock without waiting
@@ -73,13 +35,11 @@ void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts)
 	if (unlikely(in_interrupt())) {
 		/*
 		 * Readers in interrupt context will get the lock immediately
-		 * if the writer is just waiting (not holding the lock yet).
-		 * The rspin_until_writer_unlock() function returns immediately
-		 * in this case. Otherwise, they will spin (with ACQUIRE
-		 * semantics) until the lock is available without waiting in
-		 * the queue.
+		 * if the writer is just waiting (not holding the lock yet),
+		 * so spin with ACQUIRE semantics until the lock is available
+		 * without waiting in the queue.
 		 */
-		rspin_until_writer_unlock(lock, cnts);
+		atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED));
 		return;
 	}
 	atomic_sub(_QR_BIAS, &lock->cnts);
@@ -88,14 +48,14 @@ void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts)
 	 * Put the reader into the wait queue
 	 */
 	arch_spin_lock(&lock->wait_lock);
+	atomic_add(_QR_BIAS, &lock->cnts);
 
 	/*
 	 * The ACQUIRE semantics of the following spinning code ensure
 	 * that accesses can't leak upwards out of our subsequent critical
 	 * section in the case that the lock is currently held for write.
 	 */
-	cnts = atomic_fetch_add_acquire(_QR_BIAS, &lock->cnts);
-	rspin_until_writer_unlock(lock, cnts);
+	atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED));
 
 	/*
 	 * Signal the next one in queue to become queue head
@@ -110,8 +70,6 @@ EXPORT_SYMBOL(queued_read_lock_slowpath);
  */
 void queued_write_lock_slowpath(struct qrwlock *lock)
 {
-	u32 cnts;
-
 	/* Put the writer into the wait queue */
 	arch_spin_lock(&lock->wait_lock);
 
@@ -120,30 +78,14 @@ void queued_write_lock_slowpath(struct qrwlock *lock)
 	    (atomic_cmpxchg_acquire(&lock->cnts, 0, _QW_LOCKED) == 0))
 		goto unlock;
 
-	/*
-	 * Set the waiting flag to notify readers that a writer is pending,
-	 * or wait for a previous writer to go away.
-	 */
-	for (;;) {
-		struct __qrwlock *l = (struct __qrwlock *)lock;
-
-		if (!READ_ONCE(l->wmode) &&
-		   (cmpxchg_relaxed(&l->wmode, 0, _QW_WAITING) == 0))
-			break;
+	/* Set the waiting flag to notify readers that a writer is pending */
+	atomic_add(_QW_WAITING, &lock->cnts);
 
-		cpu_relax();
-	}
-
-	/* When no more readers, set the locked flag */
-	for (;;) {
-		cnts = atomic_read(&lock->cnts);
-		if ((cnts == _QW_WAITING) &&
-		    (atomic_cmpxchg_acquire(&lock->cnts, _QW_WAITING,
-					    _QW_LOCKED) == _QW_WAITING))
-			break;
-
-		cpu_relax();
-	}
+	/* When no more readers or writers, set the locked flag */
+	do {
+		atomic_cond_read_acquire(&lock->cnts, VAL == _QW_WAITING);
+	} while (atomic_cmpxchg_relaxed(&lock->cnts, _QW_WAITING,
+					_QW_LOCKED) != _QW_WAITING);
 unlock:
 	arch_spin_unlock(&lock->wait_lock);
 }