From: David Herrmann <dh.herrmann at gmail.com>
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 at gmail.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 37f6173..716c091 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[] = {
@@ -378,9 +379,9 @@ 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);
@@ -393,15 +394,16 @@ struct backlight_device *backlight_device_get_by_type(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 ? bd : NULL;
}
@@ -418,9 +420,9 @@ 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);
--
2.9.3
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