Shutdown cache_reaper when cpu goes down

Shutdown the cache_reaper in slab.c if the cpu is brought down
and set the cache_reap.func to NULL. Otherwise hotplug shuts
down the reaper for good.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.20-rc6/mm/slab.c
===================================================================
--- linux-2.6.20-rc6.orig/mm/slab.c	2007-01-29 13:43:11.679697843 -0600
+++ linux-2.6.20-rc6/mm/slab.c	2007-01-29 13:44:15.999843374 -0600
@@ -1269,10 +1269,15 @@ static int __cpuinit cpuup_callback(stru
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
 	case CPU_DOWN_PREPARE:
+		/* Shutdown cache reaper */
+		cancel_rearming_delayed_work(&per_cpu(reap_work, cpu));
+		per_cpu(reap_work, cpu).work.func = NULL;
+
 		mutex_lock(&cache_chain_mutex);
 		break;
 	case CPU_DOWN_FAILED:
 		mutex_unlock(&cache_chain_mutex);
+		start_cpu_timer(cpu);
 		break;
 	case CPU_DEAD:
 		/*