linux-kernel - Re: Re: [PATCH] regulator: recursive locking detected

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Message-ID: <CEE6BB42CAD6E947908279175AF8470A0C79DED455@EXDCVYMBSTM006.EQ1STM.local>
Date:	Fri, 1 Apr 2011 12:03:42 +0200
From:	Robert ROSENGREN <robert.rosengren@...ricsson.com>
To:	"lrg@...mlogic.co.uk" <lrg@...mlogic.co.uk>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>
Cc:	Bengt JONSSON <bengt.g.jonsson@...ricsson.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>
Subject: Re: Re: [PATCH] regulator: recursive locking detected

Regrettably, this patch came out only in half. Please disregard, updated
patch will be sent instantly. Sorry for my spamming!

BR,
Robert

On Fri, 2011-04-01 at 11:33 +0200, Robert ROSENGREN wrote:
> "possible recursive locking detected"-warnings are issued when a
> regulator has specified supply regulator. Both when enabling and
> disabling regulators uses recursive call chains for notify the supply
> regulators. This is due to locking mutexes of the same lock class,
> i.e. the locks reside in the regulator_dev struct.
> 
> Since this is valid behavior for the regulators, this patch changes the
> mutex lock into nested, as suggested in lockdep-design.txt.
> 
> Signed-off-by: Robert Rosengren <robert.rosengren@...ricsson.com>
> Acked-by: Linus Walleij <linus.walleij@...aro.org>
> ---
>  drivers/regulator/core.c |   20 ++++++++++++--------
>  1 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index 3ffc697..2a66c6b 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c
> @@ -87,7 +87,7 @@ static int _regulator_get_voltage(struct regulator_dev *rdev);
>  static int _regulator_get_current_limit(struct regulator_dev *rdev);
>  static unsigned int _regulator_get_mode(struct regulator_dev *rdev);
>  static void _notifier_call_chain(struct regulator_dev *rdev,
> -				  unsigned long event, void *data);
> +				  unsigned long event, void *data, int lock_sublevel);
>  static int _regulator_do_set_voltage(struct regulator_dev *rdev,
>  				     int min_uV, int max_uV);
>  
> @@ -1407,7 +1407,7 @@ static int _regulator_disable(struct regulator_dev *rdev,
>  			trace_regulator_disable_complete(rdev_get_name(rdev));
>  
>  			_notifier_call_chain(rdev, REGULATOR_EVENT_DISABLE,
> -					     NULL);
> +					     NULL, 0);
>  		}
>  
>  		/* decrease our supplies ref count and disable if required */
> @@ -1477,7 +1477,7 @@ static int _regulator_force_disable(struct regulator_dev *rdev,
>  		}
>  		/* notify other consumers that power has been forced off */
>  		_notifier_call_chain(rdev, REGULATOR_EVENT_FORCE_DISABLE |
> -			REGULATOR_EVENT_DISABLE, NULL);
> +			REGULATOR_EVENT_DISABLE, NULL, 0);
>  	}
>  
>  	/* decrease our supplies ref count and disable if required */
> @@ -1699,7 +1699,7 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
>  
>  	if (ret == 0)
>  		_notifier_call_chain(rdev, REGULATOR_EVENT_VOLTAGE_CHANGE,
> -				     NULL);
> +				     NULL, 0);
>  
>  	trace_regulator_set_voltage_complete(rdev_get_name(rdev), selector);
>  
> @@ -2167,19 +2167,23 @@ EXPORT_SYMBOL_GPL(regulator_unregister_notifier);
>  
>  /* notify regulator consumers and downstream regulator consumers.
>   * Note mutex must be held by caller.
> + * lock_sublevel should always be 0, only used for recursive calls.
>   */
>  static void _notifier_call_chain(struct regulator_dev *rdev,
> -				  unsigned long event, void *data)
> +				  unsigned long event, void *data, int lock_sublevel)
>  {
>  	struct regulator_dev *_rdev;
>  
>  	/* call rdev chain first */
>  	blocking_notifier_call_chain(&rdev->notifier, event, NULL);
>  
> +	/* increase sublevel before stepping into nested regulators */
> +	lock_sublevel++;
> +
>  	/* now notify regulator we supply */
>  	list_for_each_entry(_rdev, &rdev->supply_list, slist) {
> -		mutex_lock(&_rdev->mutex);
> -		_notifier_call_chain(_rdev, event, data);
> +		mutex_lock_nested(&_rdev->mutex, lock_sublevel);
> +		_notifier_call_chain(_rdev, event, data, lock_sublevel);
>  		mutex_unlock(&_rdev->mutex);
>  	}
>  }
> @@ -2333,7 +2337,7 @@ EXPORT_SYMBOL_GPL(regulator_bulk_free);
>  int regulator_notifier_call_chain(struct regulator_dev *rdev,
>  				  unsigned long event, void *data)
>  {
> -	_notifier_call_chain(rdev, event, data);
> +	_notifier_call_chain(rdev, event, data, 0);
>  	return NOTIFY_DONE;
>  
>  }
> -- 
> 1.7.4.1
> 


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