linux-kernel - Re: [PATCH v2] CPU hotplug, freezer: Fix bugs in CPU hotplug call path

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Message-ID: <CAM_iQpXDDeOzZ0L8MYFPhi_5rJJvinOD57nWWKfnCRxa_Jtx6Q@mail.gmail.com>
Date:	Sat, 8 Oct 2011 20:52:37 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Rafael J. Wysocki" <rjw@...k.pl>, pavel@....cz,
	len.brown@...el.com, mingo@...e.hu, akpm@...ux-foundation.org,
	suresh.b.siddha@...el.com, lucas.demarchi@...fusion.mobi,
	linux-pm@...ts.linux-foundation.org, rusty@...tcorp.com.au,
	vatsa@...ux.vnet.ibm.com, ashok.raj@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] CPU hotplug, freezer: Fix bugs in CPU hotplug call path

On Sat, Oct 8, 2011 at 4:56 AM, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
> index 1effc8b..75c65d6 100644
> --- a/include/linux/freezer.h
> +++ b/include/linux/freezer.h
> @@ -7,6 +7,9 @@
>  #include <linux/wait.h>
>
>  #ifdef CONFIG_FREEZER
> +
> +extern struct mutex freezer_lock;
> +
[...]
>  static inline int try_to_freeze(void)
>  {
>        if (freezing(current)) {
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 12b7458..b94c8f6 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -15,6 +15,7 @@
>  #include <linux/stop_machine.h>
>  #include <linux/mutex.h>
>  #include <linux/gfp.h>
> +#include <linux/freezer.h>
>
>  #ifdef CONFIG_SMP
>  /* Serializes the updates to cpu_online_mask, cpu_present_mask */
> @@ -280,7 +281,9 @@ int __ref cpu_down(unsigned int cpu)
>                goto out;
>        }
>
> -       err = _cpu_down(cpu, 0);
> +       mutex_lock(&freezer_lock);
> +       err = _cpu_down(cpu, tasks_are_frozen());
> +       mutex_unlock(&freezer_lock);
>

Can this even be compiled when CONFIG_FREEZER=n?
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