locking/arch, alpha: Add __down_read_killable()

Similar to __down_write_killable(), and read killable primitive.

Signed-off-by: Kirill Tkhai <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/150670115677.23930.5711263025537758463.stgit@localhost.localdomain
Signed-off-by: Ingo Molnar <[email protected]>

Author: Kirill Tkhai

arch/alpha/include/asm/rwsem.h

@@ -21,7 +21,7 @@
 #define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
 #define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
 
-static inline void __down_read(struct rw_semaphore *sem)
+static inline int ___down_read(struct rw_semaphore *sem)
 {
 	long oldcount;
 #ifndef	CONFIG_SMP
@@ -41,10 +41,24 @@ static inline void __down_read(struct rw_semaphore *sem)
 	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
 	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
 #endif
-	if (unlikely(oldcount < 0))
+	return (oldcount < 0);
+}
+
+static inline void __down_read(struct rw_semaphore *sem)
+{
+	if (unlikely(___down_read(sem)))
 		rwsem_down_read_failed(sem);
 }
 
+static inline int __down_read_killable(struct rw_semaphore *sem)
+{
+	if (unlikely(___down_read(sem)))
+		if (IS_ERR(rwsem_down_read_failed_killable(sem)))
+			return -EINTR;
+
+	return 0;
+}
+
 /*
  * trylock for reading -- returns 1 if successful, 0 if contention
  */
@@ -94,9 +108,10 @@ static inline void __down_write(struct rw_semaphore *sem)
 
 static inline int __down_write_killable(struct rw_semaphore *sem)
 {
-	if (unlikely(___down_write(sem)))
+	if (unlikely(___down_write(sem))) {
 		if (IS_ERR(rwsem_down_write_failed_killable(sem)))
 			return -EINTR;
+	}
 
 	return 0;
 }