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1da177e4 LT |
1 | #include <linux/module.h> |
2 | #include <linux/spinlock.h> | |
3 | #include <asm/atomic.h> | |
4 | #include <asm/system.h> | |
5 | ||
6 | /* | |
7 | * This is an implementation of the notion of "decrement a | |
8 | * reference count, and return locked if it decremented to zero". | |
9 | * | |
10 | * This implementation can be used on any architecture that | |
11 | * has a cmpxchg, and where atomic->value is an int holding | |
12 | * the value of the atomic (i.e. the high bits aren't used | |
13 | * for a lock or anything like that). | |
1da177e4 | 14 | */ |
1da177e4 LT |
15 | int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) |
16 | { | |
17 | int counter; | |
18 | int newcount; | |
19 | ||
20 | for (;;) { | |
21 | counter = atomic_read(atomic); | |
22 | newcount = counter - 1; | |
23 | if (!newcount) | |
24 | break; /* do it the slow way */ | |
25 | ||
26 | newcount = cmpxchg(&atomic->counter, counter, newcount); | |
27 | if (newcount == counter) | |
28 | return 0; | |
29 | } | |
30 | ||
31 | spin_lock(lock); | |
32 | if (atomic_dec_and_test(atomic)) | |
33 | return 1; | |
34 | spin_unlock(lock); | |
35 | return 0; | |
36 | } | |
37 | ||
38 | EXPORT_SYMBOL(_atomic_dec_and_lock); |