linux-kernel - Re: [SLAB] Shutdown cache

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Message-ID: <Pine.LNX.4.64.0702011517110.9210@schroedinger.engr.sgi.com>
Date:	Thu, 1 Feb 2007 15:19:33 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	akpm@...l.org
cc:	Oleg Nesterov <oleg@...sign.ru>, linux-kernel@...r.kernel.org
Subject: Re: [SLAB] Shutdown cache_reaper when cpu goes down

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@....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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