Re: [SLAB] Shutdown cache_reaper when cpu goes down

[Christoph Lameter <clameter@sgi.com>]

The comments do not explain correctly what is going on. Sorry Oleg but it 
seems that the protection of the assignment to reap_work is different that 
what we initially thought.

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

Index: current/mm/slab.c
===================================================================
--- current.orig/mm/slab.c	2007-02-01 15:07:09.000000000 -0800
+++ current/mm/slab.c	2007-02-01 15:09:21.000000000 -0800
@@ -1274,10 +1274,12 @@ static int __cpuinit cpuup_callback(stru
   	case CPU_DOWN_PREPARE:
 		/*
 		 * Shutdown cache reaper. Note that the cache_chain_mutex is
-		 * held so that cache_reap() cannot modify reap_work
-		 * concurrently.
+		 * held so that if cache_reap() is invoked it cannot do
+		 * anything expensive but will only modify reap_work
+		 * and reschedule the timer.
 		*/
 		cancel_rearming_delayed_work(&per_cpu(reap_work, cpu));
+		/* Now the cache_reaper is guaranteed to be not running. */
 		per_cpu(reap_work, cpu).work.func = NULL;
   		break;
   	case CPU_DOWN_FAILED:
-
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