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Message-Id: <1248936657.6987.3095.camel@twins>
Date: Thu, 30 Jul 2009 08:50:57 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Xiao Guangrong <xiaoguangrong@...fujitsu.com>, mingo@...e.hu,
jens.axboe@...cle.com, nickpiggin@...oo.com.au,
rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3 -mm] generic-ipi: fix the race between
generic_smp_call_function_*() and hotplug_cfd()
On Wed, 2009-07-29 at 16:31 -0700, Andrew Morton wrote:
> -void generic_smp_call_function_interrupt(void)
> +static void
> +__generic_smp_call_function_interrupt(int cpu, int run_callbacks)
> {
> struct call_function_data *data;
> - int cpu = smp_processor_id();
>
> /*
> * Ensure entry is visible on call_function_queue after we have
> @@ -169,12 +165,18 @@ void generic_smp_call_function_interrupt
> +static void
> +__generic_smp_call_function_single_interrupt(int cpu, int run_callbacks)
> {
> - struct call_single_queue *q = &__get_cpu_var(call_single_queue);
> + struct call_single_queue *q = &per_cpu(call_single_queue, cpu);
> unsigned int data_flags;
> LIST_HEAD(list);
>
It introduces this run_callbacks thing to two functions, but nothing
actually uses that... makes me suspicious there's something missing.
> case CPU_DEAD_FROZEN:
> + local_irq_save(flags);
> + __generic_smp_call_function_interrupt(cpu, 0);
> + __generic_smp_call_function_single_interrupt(cpu, 0);
> + local_irq_restore(flags);
Doing the callbacks from a different cpu than they were queued on seems
like a fine way to mess things up.
--
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