[PATCH] Directed yield: direct yield of spinlocks for powerpc

Powerpc already has a directed yield for CONFIG_PREEMPT="n".  To make it
work with CONFIG_PREEMPT="y" as well the _raw_{spin,read,write}_relax
primitives need to be defined to call __spin_yield() for spinlocks and
__rw_yield() for rw-locks.

Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-powerpc/spinlock.h

@@ -285,9 +285,9 @@ static __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
 	rw->lock = 0;
 }
 
-#define _raw_spin_relax(lock)	cpu_relax()
-#define _raw_read_relax(lock)	cpu_relax()
-#define _raw_write_relax(lock)	cpu_relax()
+#define _raw_spin_relax(lock)	__spin_yield(lock)
+#define _raw_read_relax(lock)	__rw_yield(lock)
+#define _raw_write_relax(lock)	__rw_yield(lock)
 
 #endif /* __KERNEL__ */
 #endif /* __ASM_SPINLOCK_H */