linux-kernel - RE: [PATCH] Fix the race between smp_call

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Message-ID: <1331891364.18960.221.camel@twins>
Date:	Fri, 16 Mar 2012 10:49:24 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yanmin Zhang <yanmin_zhang@...ux.intel.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: RE: [PATCH] Fix the race between smp_call_function and CPU booting

On Fri, 2012-03-16 at 06:24 +0000, Liu, Chuansheng wrote:

> Based on your patch, I did a little modification, how do you think of that?

> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -640,8 +640,10 @@ void set_cpu_present(unsigned int cpu, bool present)
>  
>  void set_cpu_online(unsigned int cpu, bool online)
>  {
> -       if (online)
> +       if (online) {
>                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
> +               cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
> +       }
>         else
>                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
>  }

I'm thinking this lacks rationale. What was wrong, Why does this fix it.
If you can't answer that stop tinkering and start thinking.
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