Re: slab: start_cpu_timer/cache_reap CONFIG_HOTPLUG_CPU problems

[Christoph Lameter]

On Tue, 30 Jan 2007, Oleg Nesterov wrote:

> Now we have 2 additional events, CPU_LOCK_ACQUIRE/CPU_LOCK_RELEASE,
> so cpuup_callback() can use them to lock/unlock cache_chain_mutex,
> but this is not related.

Then we wont need to do the mutex_lock/unlock in CPU_DOWN_XX 
anymore, right? Which brings us to this form of the patch:


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@xxxxxxx>

Index: linux-2.6.20-rc6-mm2/mm/slab.c
===================================================================
--- linux-2.6.20-rc6-mm2.orig/mm/slab.c	2007-01-29 14:27:34.199229828 -0600
+++ linux-2.6.20-rc6-mm2/mm/slab.c	2007-01-29 15:47:18.293962726 -0600
@@ -1271,6 +1271,14 @@ static int __cpuinit cpuup_callback(stru
 		start_cpu_timer(cpu);
 		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;
+  		break;
+  	case CPU_DOWN_FAILED:
+		start_cpu_timer(cpu);
+  		break;
 	case CPU_DEAD:
 		/*
 		 * Even if all the cpus of a node are down, we don't free the
-
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