Merge branch 'x86-rwsem-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-rwsem-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86-64, rwsem: Avoid store forwarding hazard in __downgrade_write
  x86-64, rwsem: 64-bit xadd rwsem implementation
  x86: Fix breakage of UML from the changes in the rwsem system
  x86-64: support native xadd rwsem implementation
  x86: clean up rwsem type system

1 files changed, 38 insertions, 21 deletions

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index 41362002476..606ede12697 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -41,6 +41,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/lockdep.h>
+#include <asm/asm.h>
 
 struct rwsem_waiter;
 
@@ -55,17 +56,28 @@ extern asmregparm struct rw_semaphore *
 
 /*
  * the semaphore definition
+ *
+ * The bias values and the counter type limits the number of
+ * potential readers/writers to 32767 for 32 bits and 2147483647
+ * for 64 bits.
  */
 
-#define RWSEM_UNLOCKED_VALUE		0x00000000
-#define RWSEM_ACTIVE_BIAS		0x00000001
-#define RWSEM_ACTIVE_MASK		0x0000ffff
-#define RWSEM_WAITING_BIAS		(-0x00010000)
+#ifdef CONFIG_X86_64
+# define RWSEM_ACTIVE_MASK		0xffffffffL
+#else
+# define RWSEM_ACTIVE_MASK		0x0000ffffL
+#endif
+
+#define RWSEM_UNLOCKED_VALUE		0x00000000L
+#define RWSEM_ACTIVE_BIAS		0x00000001L
+#define RWSEM_WAITING_BIAS		(-RWSEM_ACTIVE_MASK-1)
 #define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
 #define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
 
+typedef signed long rwsem_count_t;
+
 struct rw_semaphore {
-	signed long		count;
+	rwsem_count_t		count;
 	spinlock_t		wait_lock;
 	struct list_head	wait_list;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -105,7 +117,7 @@ do {								\
 static inline void __down_read(struct rw_semaphore *sem)
 {
 	asm volatile("# beginning down_read\n\t"
-		     LOCK_PREFIX "  inc%z0      (%1)\n\t"
+		     LOCK_PREFIX _ASM_INC "(%1)\n\t"
 		     /* adds 0x00000001, returns the old value */
 		     "  jns        1f\n"
 		     "  call call_rwsem_down_read_failed\n"
@@ -121,7 +133,7 @@ static inline void __down_read(struct rw_semaphore *sem)
  */
 static inline int __down_read_trylock(struct rw_semaphore *sem)
 {
-	__s32 result, tmp;
+	rwsem_count_t result, tmp;
 	asm volatile("# beginning __down_read_trylock\n\t"
 		     "  mov          %0,%1\n\t"
 		     "1:\n\t"
@@ -143,7 +155,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
  */
 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 {
-	int tmp;
+	rwsem_count_t tmp;
 
 	tmp = RWSEM_ACTIVE_WRITE_BIAS;
 	asm volatile("# beginning down_write\n\t"
@@ -170,9 +182,9 @@ static inline void __down_write(struct rw_semaphore *sem)
  */
 static inline int __down_write_trylock(struct rw_semaphore *sem)
 {
-	signed long ret = cmpxchg(&sem->count,
-				  RWSEM_UNLOCKED_VALUE,
-				  RWSEM_ACTIVE_WRITE_BIAS);
+	rwsem_count_t ret = cmpxchg(&sem->count,
+				    RWSEM_UNLOCKED_VALUE,
+				    RWSEM_ACTIVE_WRITE_BIAS);
 	if (ret == RWSEM_UNLOCKED_VALUE)
 		return 1;
 	return 0;
@@ -183,7 +195,7 @@ static inline int __down_write_trylock(struct rw_semaphore *sem)
  */
 static inline void __up_read(struct rw_semaphore *sem)
 {
-	__s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
+	rwsem_count_t tmp = -RWSEM_ACTIVE_READ_BIAS;
 	asm volatile("# beginning __up_read\n\t"
 		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"
 		     /* subtracts 1, returns the old value */
@@ -201,7 +213,7 @@ static inline void __up_read(struct rw_semaphore *sem)
  */
 static inline void __up_write(struct rw_semaphore *sem)
 {
-	unsigned long tmp;
+	rwsem_count_t tmp;
 	asm volatile("# beginning __up_write\n\t"
 		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"
 		     /* tries to transition
@@ -221,33 +233,38 @@ static inline void __up_write(struct rw_semaphore *sem)
 static inline void __downgrade_write(struct rw_semaphore *sem)
 {
 	asm volatile("# beginning __downgrade_write\n\t"
-		     LOCK_PREFIX "  add%z0    %2,(%1)\n\t"
-		     /* transitions 0xZZZZ0001 -> 0xYYYY0001 */
+		     LOCK_PREFIX _ASM_ADD "%2,(%1)\n\t"
+		     /*
+		      * transitions 0xZZZZ0001 -> 0xYYYY0001 (i386)
+		      *     0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64)
+		      */
 		     "  jns       1f\n\t"
 		     "  call call_rwsem_downgrade_wake\n"
 		     "1:\n\t"
 		     "# ending __downgrade_write\n"
 		     : "+m" (sem->count)
-		     : "a" (sem), "i" (-RWSEM_WAITING_BIAS)
+		     : "a" (sem), "er" (-RWSEM_WAITING_BIAS)
 		     : "memory", "cc");
 }
 
 /*
  * implement atomic add functionality
  */
-static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
+static inline void rwsem_atomic_add(rwsem_count_t delta,
+				    struct rw_semaphore *sem)
 {
-	asm volatile(LOCK_PREFIX "add%z0 %1,%0"
+	asm volatile(LOCK_PREFIX _ASM_ADD "%1,%0"
 		     : "+m" (sem->count)
-		     : "ir" (delta));
+		     : "er" (delta));
 }
 
 /*
  * implement exchange and add functionality
  */
-static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
+static inline rwsem_count_t rwsem_atomic_update(rwsem_count_t delta,
+						struct rw_semaphore *sem)
 {
-	int tmp = delta;
+	rwsem_count_t tmp = delta;
 
 	asm volatile(LOCK_PREFIX "xadd %0,%1"
 		     : "+r" (tmp), "+m" (sem->count)