Re: [PATCH try #2] powerdomain: convert pwrdm_mutex to rwsem

[Tony Lindgren <tony@atomide.com>]

* Paul Walmsley <paul@pwsan.com> [080507 17:54]:
> 
> Hi, 
> 
> that last patch escaped with some trailing whitespace.  Here's a fixed 
> copy.

Correction, pushing this one instead.

Tony

> - Paul
> 
> ---
> 
> 
> Convert pwrdm_mutex to pwrdm_rwsem to avoid trying to relock mutex in the
> event that the pwrdm_for_each() callback function calls something that
> triggers a pwrdm_lookup().  Problem found by Jouni Högander
> <jouni.hogander@nokia.com>
> 
> Signed-off-by: Paul Walmsley <paul@pwsan.com>
> 
> ---
> 
>  arch/arm/mach-omap2/powerdomain.c |   61 ++++++++++++++++++++-----------------
>  1 files changed, 33 insertions(+), 28 deletions(-)
> 
> 
> diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c
> index dd9f40e..939efe4 100644
> --- a/arch/arm/mach-omap2/powerdomain.c
> +++ b/arch/arm/mach-omap2/powerdomain.c
> @@ -18,7 +18,7 @@
>  #include <linux/module.h>
>  #include <linux/types.h>
>  #include <linux/delay.h>
> -#include <linux/mutex.h>
> +#include <linux/rwsem.h>
>  #include <linux/list.h>
>  #include <linux/errno.h>
>  #include <linux/err.h>
> @@ -37,8 +37,12 @@
>  /* pwrdm_list contains all registered struct powerdomains */
>  static LIST_HEAD(pwrdm_list);
>  
> -/* pwrdm_mutex protects pwrdm_list add and del ops */
> -static DEFINE_MUTEX(pwrdm_mutex);
> +/*
> + * pwrdm_rwsem protects pwrdm_list add and del ops - also reused to
> + * protect pwrdm_clkdms[] during clkdm add/del ops
> + */
> +static DECLARE_RWSEM(pwrdm_rwsem);
> +
>  
>  /* Private functions */
>  
> @@ -135,7 +139,7 @@ int pwrdm_register(struct powerdomain *pwrdm)
>  	if (!omap_chip_is(pwrdm->omap_chip))
>  		return -EINVAL;
>  
> -	mutex_lock(&pwrdm_mutex);
> +	down_write(&pwrdm_rwsem);
>  	if (_pwrdm_lookup(pwrdm->name)) {
>  		ret = -EEXIST;
>  		goto pr_unlock;
> @@ -147,7 +151,7 @@ int pwrdm_register(struct powerdomain *pwrdm)
>  	ret = 0;
>  
>  pr_unlock:
> -	mutex_unlock(&pwrdm_mutex);
> +	up_write(&pwrdm_rwsem);
>  
>  	return ret;
>  }
> @@ -164,9 +168,9 @@ int pwrdm_unregister(struct powerdomain *pwrdm)
>  	if (!pwrdm)
>  		return -EINVAL;
>  
> -	mutex_lock(&pwrdm_mutex);
> +	down_write(&pwrdm_rwsem);
>  	list_del(&pwrdm->node);
> -	mutex_unlock(&pwrdm_mutex);
> +	up_write(&pwrdm_rwsem);
>  
>  	pr_debug("powerdomain: unregistered %s\n", pwrdm->name);
>  
> @@ -187,9 +191,9 @@ struct powerdomain *pwrdm_lookup(const char *name)
>  	if (!name)
>  		return NULL;
>  
> -	mutex_lock(&pwrdm_mutex);
> +	down_read(&pwrdm_rwsem);
>  	pwrdm = _pwrdm_lookup(name);
> -	mutex_unlock(&pwrdm_mutex);
> +	up_read(&pwrdm_rwsem);
>  
>  	return pwrdm;
>  }
> @@ -198,15 +202,15 @@ struct powerdomain *pwrdm_lookup(const char *name)
>   * pwrdm_for_each - call function on each registered clockdomain
>   * @fn: callback function *
>   *
> - * Call the supplied function for each registered powerdomain.
> - * The callback function can return anything but 0 to bail
> - * out early from the iterator.	 The callback function is called with
> - * the pwrdm_mutex held, so no powerdomain structure manipulation
> + * Call the supplied function for each registered powerdomain.  The
> + * callback function can return anything but 0 to bail out early from
> + * the iterator.  The callback function is called with the pwrdm_rwsem
> + * held for reading, so no powerdomain structure manipulation
>   * functions should be called from the callback, although hardware
>   * powerdomain control functions are fine.  Returns the last return
>   * value of the callback function, which should be 0 for success or
> - * anything else to indicate failure; or -EINVAL if the function pointer
> - * is null.
> + * anything else to indicate failure; or -EINVAL if the function
> + * pointer is null.
>   */
>  int pwrdm_for_each(int (*fn)(struct powerdomain *pwrdm))
>  {
> @@ -216,13 +220,13 @@ int pwrdm_for_each(int (*fn)(struct powerdomain *pwrdm))
>  	if (!fn)
>  		return -EINVAL;
>  
> -	mutex_lock(&pwrdm_mutex);
> +	down_read(&pwrdm_rwsem);
>  	list_for_each_entry(temp_pwrdm, &pwrdm_list, node) {
>  		ret = (*fn)(temp_pwrdm);
>  		if (ret)
>  			break;
>  	}
> -	mutex_unlock(&pwrdm_mutex);
> +	up_read(&pwrdm_rwsem);
>  
>  	return ret;
>  }
> @@ -247,7 +251,8 @@ int pwrdm_add_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  
>  	pr_debug("powerdomain: associating clockdomain %s with powerdomain "
>  		 "%s\n", clkdm->name, pwrdm->name);
> -	mutex_lock(&pwrdm_mutex);
> +
> +	down_write(&pwrdm_rwsem);
>  
>  	for (i = 0; i < PWRDM_MAX_CLKDMS; i++) {
>  		if (!pwrdm->pwrdm_clkdms[i])
> @@ -273,13 +278,13 @@ int pwrdm_add_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	ret = 0;
>  
>  pac_exit:
> -	mutex_unlock(&pwrdm_mutex);
> +	up_write(&pwrdm_rwsem);
>  
>  	return ret;
>  }
>  
>  /**
> - * pwrdm_del_clkdm - remove a clockdomain to a powerdomain
> + * pwrdm_del_clkdm - remove a clockdomain from a powerdomain
>   * @pwrdm: struct powerdomain * to add the clockdomain to
>   * @clkdm: struct clockdomain * to associate with a powerdomain
>   *
> @@ -299,7 +304,7 @@ int pwrdm_del_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	pr_debug("powerdomain: dissociating clockdomain %s from powerdomain "
>  		 "%s\n", clkdm->name, pwrdm->name);
>  
> -	mutex_lock(&pwrdm_mutex);
> +	down_write(&pwrdm_rwsem);
>  
>  	for (i = 0; i < PWRDM_MAX_CLKDMS; i++)
>  		if (pwrdm->pwrdm_clkdms[i] == clkdm)
> @@ -317,7 +322,7 @@ int pwrdm_del_clkdm(struct powerdomain *pwrdm, struct clockdomain *clkdm)
>  	ret = 0;
>  
>  pdc_exit:
> -	mutex_unlock(&pwrdm_mutex);
> +	up_write(&pwrdm_rwsem);
>  
>  	return ret;
>  }
> @@ -330,10 +335,10 @@ pdc_exit:
>   * Call the supplied function for each clockdomain in the powerdomain
>   * 'pwrdm'.  The callback function can return anything but 0 to bail
>   * out early from the iterator.  The callback function is called with
> - * the pwrdm_mutex held, so no powerdomain structure manipulation
> - * functions should be called from the callback, although hardware
> - * powerdomain control functions are fine.  Returns -EINVAL if
> - * presented with invalid pointers; or passes along the last return
> + * the pwrdm_rwsem held for reading, so no powerdomain structure
> + * manipulation functions should be called from the callback, although
> + * hardware powerdomain control functions are fine.  Returns -EINVAL
> + * if presented with invalid pointers; or passes along the last return
>   * value of the callback function, which should be 0 for success or
>   * anything else to indicate failure.
>   */
> @@ -347,12 +352,12 @@ int pwrdm_for_each_clkdm(struct powerdomain *pwrdm,
>  	if (!fn)
>  		return -EINVAL;
>  
> -	mutex_lock(&pwrdm_mutex);
> +	down_read(&pwrdm_rwsem);
>  
>  	for (i = 0; i < PWRDM_MAX_CLKDMS && !ret; i++)
>  		ret = (*fn)(pwrdm, pwrdm->pwrdm_clkdms[i]);
>  
> -	mutex_unlock(&pwrdm_mutex);
> +	up_read(&pwrdm_rwsem);
>  
>  	return ret;
>  }
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html