On 01/29, Christoph Lameter wrote:
>
> 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:
Yes, if CPU_LOCK_ACQUIRE takes cache_chain_mutex, we don't need to do so
on CPU_DOWN_PREPARE. I didn't know cpuup_callback() was already converted,
sorry for the confusion!
Note: with the patch below we are doing cancel_rearming_delayed_work()
under cache_chain_mutex. This is ok since cache_reap() does mutex_trylock(),
so deadlock is not possible. However, this means that mutex_trylock() becomes
mandatory for cache_reap(), probably a little comment will be good.
> 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 <[email protected]>
>
> 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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