patch-2.4.20 linux-2.4.20/include/asm-ppc/rwsem.h

• Lines: 45
• Date: Thu Nov 28 15:53:15 2002
• Orig file: linux-2.4.19/include/asm-ppc/rwsem.h
• Orig date: Mon May 21 15:02:06 2001

diff -urN linux-2.4.19/include/asm-ppc/rwsem.h linux-2.4.20/include/asm-ppc/rwsem.h
@@ -1,5 +1,5 @@
 /*
- * BK Id: SCCS/s.rwsem.h 1.6 05/17/01 18:14:25 cort
+ * BK Id: %F% %I% %G% %U% %#%
  */
 /*
  * include/asm-ppc/rwsem.h: R/W semaphores for PPC using the stuff
@@ -77,6 +77,20 @@
 		rwsem_down_read_failed(sem);
 }
 
+static inline int __down_read_trylock(struct rw_semaphore *sem)
+{
+	int tmp;
+
+	while ((tmp = sem->count) >= 0) {
+		if (tmp == cmpxchg(&sem->count, tmp,
+				   tmp + RWSEM_ACTIVE_READ_BIAS)) {
+			smp_wmb();
+			return 1;
+		}
+	}
+	return 0;
+}
+
 /*
  * lock for writing
  */
@@ -92,6 +106,16 @@
 		rwsem_down_write_failed(sem);
 }
 
+static inline int __down_write_trylock(struct rw_semaphore *sem)
+{
+	int tmp;
+
+	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
+		      RWSEM_ACTIVE_WRITE_BIAS);
+	smp_wmb();
+	return tmp == RWSEM_UNLOCKED_VALUE;
+}
+
 /*
  * unlock after reading
  */