linux-kernel - Re: [PATCH] ACPI/hotplug: Fix STARTING/DYING action in acpi_cpu_soft

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Date:	Tue, 20 May 2014 00:55:51 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Toshi Kani <toshi.kani@...com>
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI/hotplug: Fix STARTING/DYING action in acpi_cpu_soft_notify()

On Thursday, May 08, 2014 07:58:59 AM Toshi Kani wrote:
> During CPU online/offline testing on a large system, one of the
> processors got stuck after the message "bad: scheduling from the
> idle thread!".  The problem is that acpi_cpu_soft_notify() calls
> acpi_bus_get_device() for all action types.  CPU_STARTING and
> CPU_DYING do not allow the notify handlers to sleep.  However,
> acpi_bus_get_device() can sleep in acpi_ut_acquire_mutex().
> 
> Change acpi_cpu_soft_notify() to return immediately for CPU_STARTING
> and CPU_DYING as they have no action in this handler.
> 
> Signed-off-by: Toshi Kani <toshi.kani@...com>

Queued up for 3.16, thanks!

> ---
>  drivers/acpi/processor_driver.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index 7f70f31..4fcbd67 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -121,6 +121,13 @@ static int acpi_cpu_soft_notify(struct notifier_block *nfb,
>  	struct acpi_processor *pr = per_cpu(processors, cpu);
>  	struct acpi_device *device;
>  
> +	/*
> +	 * CPU_STARTING and CPU_DYING must not sleep. Return here since
> +	 * acpi_bus_get_device() may sleep.
> +	 */
> +	if (action == CPU_STARTING || action == CPU_DYING)
> +		return NOTIFY_DONE;
> +
>  	if (!pr || acpi_bus_get_device(pr->handle, &device))
>  		return NOTIFY_DONE;
>  
> --
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-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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