linux-kernel - Re: [PATCH 1/1] MM: slqb, fix per

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Date:	Mon, 2 Nov 2009 23:53:30 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	npiggin@...e.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH 1/1] MM: slqb, fix per_cpu access

On Mon, 2 Nov 2009 08:42:58 am Jiri Slaby wrote:
> We cannot use the same local variable name as the declared per_cpu
> variable since commit "percpu: remove per_cpu__ prefix."
> 
> Otherwise we would see crashes like:
> general protection fault: 0000 [#1] SMP
> last sysfs file:
> CPU 1
> Modules linked in:
> Pid: 1, comm: swapper Tainted: G        W  2.6.32-rc5-mm1_64 #860
> RIP: 0010:[<ffffffff8142ff94>]  [<ffffffff8142ff94>] start_cpu_timer+0x2b/0x87
> ...
> 
> Signed-off-by: Jiri Slaby <jirislaby@...il.com>
> Cc: Nick Piggin <npiggin@...e.de>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Cc: Christoph Lameter <cl@...ux-foundation.org>
> ---
>  mm/slqb.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/slqb.c b/mm/slqb.c
> index e745d9a..27f5025 100644
> --- a/mm/slqb.c
> +++ b/mm/slqb.c
> @@ -2770,16 +2770,16 @@ static DEFINE_PER_CPU(struct delayed_work, cache_trim_work);
>  
>  static void __cpuinit start_cpu_timer(int cpu)
>  {
> -	struct delayed_work *cache_trim_work = &per_cpu(cache_trim_work, cpu);
> +	struct delayed_work *_cache_trim_work = &per_cpu(cache_trim_work, cpu);
>  
>  	/*
>  	 * When this gets called from do_initcalls via cpucache_init(),
>  	 * init_workqueues() has already run, so keventd will be setup
>  	 * at that time.
>  	 */
> -	if (keventd_up() && cache_trim_work->work.func == NULL) {
> -		INIT_DELAYED_WORK(cache_trim_work, cache_trim_worker);
> -		schedule_delayed_work_on(cpu, cache_trim_work,
> +	if (keventd_up() && _cache_trim_work->work.func == NULL) {
> +		INIT_DELAYED_WORK(_cache_trim_work, cache_trim_worker);
> +		schedule_delayed_work_on(cpu, _cache_trim_work,
>  					__round_jiffies_relative(HZ, cpu));

How about calling the local var "trim"?

This actually makes the code more readable, IMHO.

Thanks,
Rusty.
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