linux-kernel - Re: [PATCH] wakeup: Use irqsave/irqrestore for events

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Message-Id: <201209062335.23013.rjw@sisk.pl>
Date:	Thu, 6 Sep 2012 23:35:22 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	John Stultz <john.stultz@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Android Team <kernel-team@...roid.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>
Subject: Re: [PATCH] wakeup: Use irqsave/irqrestore for events_lock

On Thursday, September 06, 2012, John Stultz wrote:
> Jon Medhurst (Tixy) recently noticed a problem with the
> events_lock usage. One of the Android patches that uses
> wakeup_sources calls wakeup_source_add() with irqs disabled.
> However, the event_lock usage in wakeup_source_add() uses
> spin_lock_irq()/spin_unlock_irq(), which reenables interrupts.
> This results in lockdep warnings.
> 
> The fix is to use spin_lock_irqsave()/spin_lock_irqrestore()
> instead for the events_lock.
> 
> Full bug report here:
> https://bugs.launchpad.net/linaro-landing-team-arm/+bug/1037565
> 
> Cc: Rafael J. Wysocki <rjw@...k.pl>
> Cc: Android Team <kernel-team@...roid.com>
> Cc: Arve Hjønnevåg <arve@...roid.com>
> Cc: Jon Medhurst (Tixy) <tixy@...aro.org>
> Reported-and-debugged-by: Jon Medhurst (Tixy) <tixy@...aro.org>
> Signed-off-by: John Stultz <john.stultz@...aro.org>

Thanks, applied to the linux-next brach of the linux-pm.git tree as v3.7
material.

Please consider CCing PM-related patches to linux-pm@...r.kernel.org in the
future, that makes it much easier for me to handle them.

Thanks,
Rafael


> ---
>  drivers/base/power/wakeup.c |   17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> index cbb463b..0e4b093 100644
> --- a/drivers/base/power/wakeup.c
> +++ b/drivers/base/power/wakeup.c
> @@ -127,6 +127,8 @@ EXPORT_SYMBOL_GPL(wakeup_source_destroy);
>   */
>  void wakeup_source_add(struct wakeup_source *ws)
>  {
> +	unsigned long flags;
> +
>  	if (WARN_ON(!ws))
>  		return;
>  
> @@ -135,9 +137,9 @@ void wakeup_source_add(struct wakeup_source *ws)
>  	ws->active = false;
>  	ws->last_time = ktime_get();
>  
> -	spin_lock_irq(&events_lock);
> +	spin_lock_irqsave(&events_lock, flags);
>  	list_add_rcu(&ws->entry, &wakeup_sources);
> -	spin_unlock_irq(&events_lock);
> +	spin_unlock_irqrestore(&events_lock, flags);
>  }
>  EXPORT_SYMBOL_GPL(wakeup_source_add);
>  
> @@ -147,12 +149,14 @@ EXPORT_SYMBOL_GPL(wakeup_source_add);
>   */
>  void wakeup_source_remove(struct wakeup_source *ws)
>  {
> +	unsigned long flags;
> +
>  	if (WARN_ON(!ws))
>  		return;
>  
> -	spin_lock_irq(&events_lock);
> +	spin_lock_irqsave(&events_lock, flags);
>  	list_del_rcu(&ws->entry);
> -	spin_unlock_irq(&events_lock);
> +	spin_unlock_irqrestore(&events_lock, flags);
>  	synchronize_rcu();
>  }
>  EXPORT_SYMBOL_GPL(wakeup_source_remove);
> @@ -723,15 +727,16 @@ bool pm_get_wakeup_count(unsigned int *count, bool block)
>  bool pm_save_wakeup_count(unsigned int count)
>  {
>  	unsigned int cnt, inpr;
> +	unsigned long flags;
>  
>  	events_check_enabled = false;
> -	spin_lock_irq(&events_lock);
> +	spin_lock_irqsave(&events_lock, flags);
>  	split_counters(&cnt, &inpr);
>  	if (cnt == count && inpr == 0) {
>  		saved_count = count;
>  		events_check_enabled = true;
>  	}
> -	spin_unlock_irq(&events_lock);
> +	spin_unlock_irqrestore(&events_lock, flags);
>  	return events_check_enabled;
>  }
>  
> 

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