kfifo: move out spinlock

Move the pointer to the spinlock out of struct kfifo.  Most users in
tree do not actually use a spinlock, so the few exceptions now have to
call kfifo_{get,put}_locked, which takes an extra argument to a
spinlock.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 45 deletions

diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index c3f8d82efd34..e0f5c9d4197d 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -30,13 +30,12 @@ struct kfifo {
 	unsigned int size;	/* the size of the allocated buffer */
 	unsigned int in;	/* data is added at offset (in % size) */
 	unsigned int out;	/* data is extracted from off. (out % size) */
-	spinlock_t *lock;	/* protects concurrent modifications */
 };
 
 extern void kfifo_init(struct kfifo *fifo, unsigned char *buffer,
-			unsigned int size, spinlock_t *lock);
+			unsigned int size);
 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
-			gfp_t gfp_mask, spinlock_t *lock);
+			gfp_t gfp_mask);
 extern void kfifo_free(struct kfifo *fifo);
 extern unsigned int __kfifo_put(struct kfifo *fifo,
 				const unsigned char *buffer, unsigned int len);
@@ -58,58 +57,67 @@ static inline void __kfifo_reset(struct kfifo *fifo)
  */
 static inline void kfifo_reset(struct kfifo *fifo)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(fifo->lock, flags);
-
 	__kfifo_reset(fifo);
+}
+
+/**
+ * __kfifo_len - returns the number of bytes available in the FIFO
+ * @fifo: the fifo to be used.
+ */
+static inline unsigned int __kfifo_len(struct kfifo *fifo)
+{
+	register unsigned int	out;
 
-	spin_unlock_irqrestore(fifo->lock, flags);
+	out = fifo->out;
+	smp_rmb();
+	return fifo->in - out;
 }
 
 /**
- * kfifo_put - puts some data into the FIFO
+ * kfifo_put_locked - puts some data into the FIFO using a spinlock for locking
  * @fifo: the fifo to be used.
- * @buffer: the data to be added.
- * @len: the length of the data to be added.
+ * @from: the data to be added.
+ * @n: the length of the data to be added.
+ * @lock: pointer to the spinlock to use for locking.
  *
- * This function copies at most @len bytes from the @buffer into
+ * This function copies at most @len bytes from the @from buffer into
  * the FIFO depending on the free space, and returns the number of
  * bytes copied.
  */
-static inline unsigned int kfifo_put(struct kfifo *fifo,
-				const unsigned char *buffer, unsigned int len)
+static inline __must_check unsigned int kfifo_put_locked(struct kfifo *fifo,
+		const unsigned char *from, unsigned int n, spinlock_t *lock)
 {
 	unsigned long flags;
 	unsigned int ret;
 
-	spin_lock_irqsave(fifo->lock, flags);
+	spin_lock_irqsave(lock, flags);
 
-	ret = __kfifo_put(fifo, buffer, len);
+	ret = __kfifo_put(fifo, from, n);
 
-	spin_unlock_irqrestore(fifo->lock, flags);
+	spin_unlock_irqrestore(lock, flags);
 
 	return ret;
 }
 
 /**
- * kfifo_get - gets some data from the FIFO
+ * kfifo_get_locked - gets some data from the FIFO using a spinlock for locking
  * @fifo: the fifo to be used.
- * @buffer: where the data must be copied.
- * @len: the size of the destination buffer.
+ * @to: where the data must be copied.
+ * @n: the size of the destination buffer.
+ * @lock: pointer to the spinlock to use for locking.
  *
  * This function copies at most @len bytes from the FIFO into the
- * @buffer and returns the number of copied bytes.
+ * @to buffer and returns the number of copied bytes.
  */
-static inline unsigned int kfifo_get(struct kfifo *fifo,
-				     unsigned char *buffer, unsigned int len)
+static inline __must_check unsigned int kfifo_get_locked(struct kfifo *fifo,
+	unsigned char *to, unsigned int n, spinlock_t *lock)
 {
 	unsigned long flags;
 	unsigned int ret;
 
-	spin_lock_irqsave(fifo->lock, flags);
+	spin_lock_irqsave(lock, flags);
 
-	ret = __kfifo_get(fifo, buffer, len);
+	ret = __kfifo_get(fifo, to, n);
 
 	/*
 	 * optimization: if the FIFO is empty, set the indices to 0
@@ -118,36 +126,18 @@ static inline unsigned int kfifo_get(struct kfifo *fifo,
 	if (fifo->in == fifo->out)
 		fifo->in = fifo->out = 0;
 
-	spin_unlock_irqrestore(fifo->lock, flags);
+	spin_unlock_irqrestore(lock, flags);
 
 	return ret;
 }
 
 /**
- * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
- * @fifo: the fifo to be used.
- */
-static inline unsigned int __kfifo_len(struct kfifo *fifo)
-{
-	return fifo->in - fifo->out;
-}
-
-/**
  * kfifo_len - returns the number of bytes available in the FIFO
  * @fifo: the fifo to be used.
  */
 static inline unsigned int kfifo_len(struct kfifo *fifo)
 {
-	unsigned long flags;
-	unsigned int ret;
-
-	spin_lock_irqsave(fifo->lock, flags);
-
-	ret = __kfifo_len(fifo);
-
-	spin_unlock_irqrestore(fifo->lock, flags);
-
-	return ret;
+	return __kfifo_len(fifo);
 }
 
 #endif