linux-kernel - Re: [PATCH] ACPI / sleep: Drain outstanding events after disabling multiple GPEs

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Date:	Sat, 15 Nov 2014 02:37:49 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>
Subject: Re: [PATCH] ACPI / sleep: Drain outstanding events after disabling multiple GPEs

On Saturday, November 15, 2014 02:30:51 AM Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> After multiple GPEs have been disabled at the low level in one go,
> like when acpi_disable_all_gpes() is called, we should always drain
> all of the outstanding events from them, or the ACPICA's GPE handling
> code may re-enable one of them as a result of a race condition.

Scratch the last part.

We simply need to drain them to prevent the GPE handling code from
being executed in parallel with whatever happens after the GPEs have
been disabled.

> For this reason, call acpi_os_wait_events_complete() after
> acpi_enable_all_wakeup_gpes() and acpi_disable_all_gpes() in
> acpi_freeze_prepare() and acpi_power_off_prepare(), respectively.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/sleep.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> Index: linux-pm/drivers/acpi/sleep.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/sleep.c
> +++ linux-pm/drivers/acpi/sleep.c
> @@ -630,6 +630,7 @@ static int acpi_freeze_begin(void)
>  static int acpi_freeze_prepare(void)
>  {
>  	acpi_enable_all_wakeup_gpes();
> +	acpi_os_wait_events_complete();
>  	enable_irq_wake(acpi_gbl_FADT.sci_interrupt);
>  	return 0;
>  }
> @@ -825,6 +826,7 @@ static void acpi_power_off_prepare(void)
>  	/* Prepare to power off the system */
>  	acpi_sleep_prepare(ACPI_STATE_S5);
>  	acpi_disable_all_gpes();
> +	acpi_os_wait_events_complete();
>  }
>  
>  static void acpi_power_off(void)
> 
> --
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-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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