sh: cache secondary CPUs idle loop.

This provides a cache of the secondary CPUs idle loop for the cases where
hotplug simply enters a low power state instead of resetting or powering
off the core.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/include/asm/processor.h

@@ -85,6 +85,10 @@ struct sh_cpuinfo {
 	struct tlb_info itlb;
 	struct tlb_info dtlb;
 
+#ifdef CONFIG_SMP
+	struct task_struct *idle;
+#endif
+
 	unsigned long flags;
 } __attribute__ ((aligned(L1_CACHE_BYTES)));
 

arch/sh/kernel/smp.c

@@ -125,10 +125,15 @@ int __cpuinit __cpu_up(unsigned int cpu)
 	struct task_struct *tsk;
 	unsigned long timeout;
 
-	tsk = fork_idle(cpu);
-	if (IS_ERR(tsk)) {
-		printk(KERN_ERR "Failed forking idle task for cpu %d\n", cpu);
-		return PTR_ERR(tsk);
+	tsk = cpu_data[cpu].idle;
+	if (!tsk) {
+		tsk = fork_idle(cpu);
+		if (IS_ERR(tsk)) {
+			pr_err("Failed forking idle task for cpu %d\n", cpu);
+			return PTR_ERR(tsk);
+		}
+
+		cpu_data[cpu].idle = tsk;
 	}
 
 	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;