| Message ID | 1410364463-12692-3-git-send-email-dh.herrmann@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 10 Sep 2014, David Herrmann <dh.herrmann@gmail.com> wrote: > There is really no reason to use a mutex to protect a simple list. Convert > the list-lock to a simple spinlock instead. > > The spin-locks prepare for a backlight_find() helper, which should > preferably be usable from atomic context. A mutex would prevent that, so > use an irq-save spinlock instead. > > Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Reviewed-by: Jani Nikula <jani.nikula@intel.com> > --- > drivers/video/backlight/backlight.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c > index 726c6c6..33b64be 100644 > --- a/drivers/video/backlight/backlight.c > +++ b/drivers/video/backlight/backlight.c > @@ -16,13 +16,14 @@ > #include <linux/err.h> > #include <linux/fb.h> > #include <linux/slab.h> > +#include <linux/spinlock.h> > > #ifdef CONFIG_PMAC_BACKLIGHT > #include <asm/backlight.h> > #endif > > static LIST_HEAD(backlight_dev_list); > -static DEFINE_MUTEX(backlight_dev_list_mutex); > +static DEFINE_SPINLOCK(backlight_dev_list_lock); > static BLOCKING_NOTIFIER_HEAD(backlight_notifier); > > static const char *const backlight_types[] = { > @@ -369,9 +370,9 @@ struct backlight_device *backlight_device_register(const char *name, > mutex_unlock(&pmac_backlight_mutex); > #endif > > - mutex_lock(&backlight_dev_list_mutex); > + spin_lock_irq(&backlight_dev_list_lock); > list_add(&new_bd->entry, &backlight_dev_list); > - mutex_unlock(&backlight_dev_list_mutex); > + spin_unlock_irq(&backlight_dev_list_lock); > > blocking_notifier_call_chain(&backlight_notifier, > BACKLIGHT_REGISTERED, new_bd); > @@ -384,15 +385,16 @@ bool backlight_device_registered(enum backlight_type type) > { > bool found = false; > struct backlight_device *bd; > + unsigned long flags; > > - mutex_lock(&backlight_dev_list_mutex); > + spin_lock_irqsave(&backlight_dev_list_lock, flags); > list_for_each_entry(bd, &backlight_dev_list, entry) { > if (bd->props.type == type) { > found = true; > break; > } > } > - mutex_unlock(&backlight_dev_list_mutex); > + spin_unlock_irqrestore(&backlight_dev_list_lock, flags); > > return found; > } > @@ -409,9 +411,9 @@ void backlight_device_unregister(struct backlight_device *bd) > if (!bd) > return; > > - mutex_lock(&backlight_dev_list_mutex); > + spin_lock_irq(&backlight_dev_list_lock); > list_del(&bd->entry); > - mutex_unlock(&backlight_dev_list_mutex); > + spin_unlock_irq(&backlight_dev_list_lock); > > #ifdef CONFIG_PMAC_BACKLIGHT > mutex_lock(&pmac_backlight_mutex); > -- > 2.1.0 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 726c6c6..33b64be 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -16,13 +16,14 @@ #include <linux/err.h> #include <linux/fb.h> #include <linux/slab.h> +#include <linux/spinlock.h> #ifdef CONFIG_PMAC_BACKLIGHT #include <asm/backlight.h> #endif static LIST_HEAD(backlight_dev_list); -static DEFINE_MUTEX(backlight_dev_list_mutex); +static DEFINE_SPINLOCK(backlight_dev_list_lock); static BLOCKING_NOTIFIER_HEAD(backlight_notifier); static const char *const backlight_types[] = { @@ -369,9 +370,9 @@ struct backlight_device *backlight_device_register(const char *name, mutex_unlock(&pmac_backlight_mutex); #endif - mutex_lock(&backlight_dev_list_mutex); + spin_lock_irq(&backlight_dev_list_lock); list_add(&new_bd->entry, &backlight_dev_list); - mutex_unlock(&backlight_dev_list_mutex); + spin_unlock_irq(&backlight_dev_list_lock); blocking_notifier_call_chain(&backlight_notifier, BACKLIGHT_REGISTERED, new_bd); @@ -384,15 +385,16 @@ bool backlight_device_registered(enum backlight_type type) { bool found = false; struct backlight_device *bd; + unsigned long flags; - mutex_lock(&backlight_dev_list_mutex); + spin_lock_irqsave(&backlight_dev_list_lock, flags); list_for_each_entry(bd, &backlight_dev_list, entry) { if (bd->props.type == type) { found = true; break; } } - mutex_unlock(&backlight_dev_list_mutex); + spin_unlock_irqrestore(&backlight_dev_list_lock, flags); return found; } @@ -409,9 +411,9 @@ void backlight_device_unregister(struct backlight_device *bd) if (!bd) return; - mutex_lock(&backlight_dev_list_mutex); + spin_lock_irq(&backlight_dev_list_lock); list_del(&bd->entry); - mutex_unlock(&backlight_dev_list_mutex); + spin_unlock_irq(&backlight_dev_list_lock); #ifdef CONFIG_PMAC_BACKLIGHT mutex_lock(&pmac_backlight_mutex);
There is really no reason to use a mutex to protect a simple list. Convert the list-lock to a simple spinlock instead. The spin-locks prepare for a backlight_find() helper, which should preferably be usable from atomic context. A mutex would prevent that, so use an irq-save spinlock instead. Signed-off-by: David Herrmann <dh.herrmann@gmail.com> --- drivers/video/backlight/backlight.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)