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1da177e4 LT |
1 | /* |
2 | * MIPS version of atomic_dec_and_lock() using cmpxchg | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation; either version | |
7 | * 2 of the License, or (at your option) any later version. | |
8 | */ | |
9 | ||
10 | #include <linux/module.h> | |
11 | #include <linux/spinlock.h> | |
12 | #include <asm/atomic.h> | |
13 | #include <asm/system.h> | |
14 | ||
15 | /* | |
16 | * This is an implementation of the notion of "decrement a | |
17 | * reference count, and return locked if it decremented to zero". | |
18 | * | |
19 | * This implementation can be used on any architecture that | |
20 | * has a cmpxchg, and where atomic->value is an int holding | |
21 | * the value of the atomic (i.e. the high bits aren't used | |
22 | * for a lock or anything like that). | |
1da177e4 | 23 | */ |
1da177e4 LT |
24 | int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) |
25 | { | |
26 | int counter; | |
27 | int newcount; | |
28 | ||
29 | for (;;) { | |
30 | counter = atomic_read(atomic); | |
31 | newcount = counter - 1; | |
32 | if (!newcount) | |
33 | break; /* do it the slow way */ | |
34 | ||
35 | newcount = cmpxchg(&atomic->counter, counter, newcount); | |
36 | if (newcount == counter) | |
37 | return 0; | |
38 | } | |
39 | ||
40 | spin_lock(lock); | |
41 | if (atomic_dec_and_test(atomic)) | |
42 | return 1; | |
43 | spin_unlock(lock); | |
44 | return 0; | |
45 | } | |
46 | ||
47 | EXPORT_SYMBOL(_atomic_dec_and_lock); |