diff options
| -rw-r--r-- | include/linux/lockref.h | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/include/linux/lockref.h b/include/linux/lockref.h new file mode 100644 index 0000000..01233e0 --- /dev/null +++ b/include/linux/lockref.h @@ -0,0 +1,71 @@ +#ifndef __LINUX_LOCKREF_H +#define __LINUX_LOCKREF_H + +/* + * Locked reference counts. + * + * These are different from just plain atomic refcounts in that they + * are atomic with respect to the spinlock that goes with them. In + * particular, there can be implementations that don't actually get + * the spinlock for the common decrement/increment operations, but they + * still have to check that the operation is done semantically as if + * the spinlock had been taken (using a cmpxchg operation that covers + * both the lock and the count word, or using memory transactions, for + * example). + */ + +#include <linux/spinlock.h> + +struct lockref { + spinlock_t lock; + unsigned int count; +}; + +/** + * lockref_get - Increments reference count unconditionally + * @lockcnt: pointer to lockref structure + * + * This operation is only valid if you already hold a reference + * to the object, so you know the count cannot be zero. + */ +static inline void lockref_get(struct lockref *lockref) +{ + spin_lock(&lockref->lock); + lockref->count++; + spin_unlock(&lockref->lock); +} + +/** + * lockref_get_not_zero - Increments count unless the count is 0 + * @lockcnt: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if count is 0 + */ +static inline int lockref_get_not_zero(struct lockref *lockref) +{ + int retval = 0; + + spin_lock(&lockref->lock); + if (lockref->count) { + lockref->count++; + retval = 1; + } + spin_unlock(&lockref->lock); + return retval; +} + +/** + * lockref_put_or_lock - decrements count unless count <= 1 before decrement + * @lockcnt: pointer to lockref structure + * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken + */ +static inline int lockref_put_or_lock(struct lockref *lockref) +{ + spin_lock(&lockref->lock); + if (lockref->count <= 1) + return 0; + lockref->count--; + spin_unlock(&lockref->lock); + return 1; +} + +#endif /* __LINUX_LOCKREF_H */ |
