linux-kernel - Re: + generic-ipi-fix-the-race-between-generic_smp_call_function_-and-hotplug

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Message-Id: <1253326599.3948.732.camel@sbs-t61.sc.intel.com>
Date:	Fri, 18 Sep 2009 19:16:39 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mm-commits@...r.kernel.org" <mm-commits@...r.kernel.org>,
	"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"nickpiggin@...oo.com.au" <nickpiggin@...oo.com.au>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: +
 generic-ipi-fix-the-race-between-generic_smp_call_function_-and-hotplug_cfd.patch
 added to -mm tree

On Wed, 2009-09-16 at 20:00 -0700, Xiao Guangrong wrote: 
> How about manual check/handle pending IPI interruption in the CPU context?
> like this:
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -173,6 +173,9 @@ static int __ref take_cpu_down(void *_param)
>  	struct take_cpu_down_param *param = _param;
>  	int err;
>  
> +	generic_smp_call_function_interrupt();
> +	generic_smp_call_function_single_interrupt();
> +

At this place, how will you ensure that the smp_call_function initiated
by this dying cpu has reached and got serviced at its destination?

All the other cpu's have disabled interrupts in the stop machine state
by the time we come here and we can't wait.

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