ppc64: Make cpu_relax a barrier

arch/ppc64/kernel/irq.c

@@ -173,10 +173,8 @@ inline void synchronize_irq(unsigned int irq)
 	if (!irq_desc[irq].action)
 		return;
 
-	while (irq_desc[irq].status & IRQ_INPROGRESS) {
-		barrier();
+	while (irq_desc[irq].status & IRQ_INPROGRESS)
 		cpu_relax();
-	}
 }
 
 #endif /* CONFIG_SMP */

include/asm-ppc64/processor.h

@@ -692,7 +692,7 @@ unsigned long get_wchan(struct task_struct *p);
 #define KSTK_EIP(tsk)  ((tsk)->thread.regs? (tsk)->thread.regs->nip: 0)
 #define KSTK_ESP(tsk)  ((tsk)->thread.regs? (tsk)->thread.regs->gpr[1]: 0)
 
-#define cpu_relax()     do { } while (0)
+#define cpu_relax()     barrier()
 
 /*
  * Prefetch macros.