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git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - lib/lockref.c
1 #include <linux/export.h>
2 #include <linux/lockref.h>
4 #ifdef CONFIG_CMPXCHG_LOCKREF
7 * Note that the "cmpxchg()" reloads the "old" value for the
10 #define CMPXCHG_LOOP(CODE, SUCCESS) do { \
12 BUILD_BUG_ON(sizeof(old) != 8); \
13 old.lock_count = ACCESS_ONCE(lockref->lock_count); \
14 while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \
15 struct lockref new = old, prev = old; \
17 old.lock_count = cmpxchg(&lockref->lock_count, \
18 old.lock_count, new.lock_count); \
19 if (likely(old.lock_count == prev.lock_count)) { \
27 #define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0)
32 * lockref_get - Increments reference count unconditionally
33 * @lockcnt: pointer to lockref structure
35 * This operation is only valid if you already hold a reference
36 * to the object, so you know the count cannot be zero.
38 void lockref_get(struct lockref
*lockref
)
46 spin_lock(&lockref
->lock
);
48 spin_unlock(&lockref
->lock
);
50 EXPORT_SYMBOL(lockref_get
);
53 * lockref_get_not_zero - Increments count unless the count is 0
54 * @lockcnt: pointer to lockref structure
55 * Return: 1 if count updated successfully or 0 if count was zero
57 int lockref_get_not_zero(struct lockref
*lockref
)
69 spin_lock(&lockref
->lock
);
75 spin_unlock(&lockref
->lock
);
78 EXPORT_SYMBOL(lockref_get_not_zero
);
81 * lockref_get_or_lock - Increments count unless the count is 0
82 * @lockcnt: pointer to lockref structure
83 * Return: 1 if count updated successfully or 0 if count was zero
84 * and we got the lock instead.
86 int lockref_get_or_lock(struct lockref
*lockref
)
96 spin_lock(&lockref
->lock
);
100 spin_unlock(&lockref
->lock
);
103 EXPORT_SYMBOL(lockref_get_or_lock
);
106 * lockref_put_or_lock - decrements count unless count <= 1 before decrement
107 * @lockcnt: pointer to lockref structure
108 * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
110 int lockref_put_or_lock(struct lockref
*lockref
)
120 spin_lock(&lockref
->lock
);
121 if (lockref
->count
<= 1)
124 spin_unlock(&lockref
->lock
);
127 EXPORT_SYMBOL(lockref_put_or_lock
);