Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/lib/dec_and_lock.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 963 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | #include <linux/module.h> |
2 | #include <linux/spinlock.h> |
3 | #include <asm/atomic.h> |
4 | |
5 | /* |
6 | * This is an architecture-neutral, but slow, |
7 | * implementation of the notion of "decrement |
8 | * a reference count, and return locked if it |
9 | * decremented to zero". |
10 | * |
11 | * NOTE NOTE NOTE! This is _not_ equivalent to |
12 | * |
13 | * if (atomic_dec_and_test(&atomic)) { |
14 | * spin_lock(&lock); |
15 | * return 1; |
16 | * } |
17 | * return 0; |
18 | * |
19 | * because the spin-lock and the decrement must be |
20 | * "atomic". |
21 | * |
22 | * This slow version gets the spinlock unconditionally, |
23 | * and releases it if it isn't needed. Architectures |
24 | * are encouraged to come up with better approaches, |
25 | * this is trivially done efficiently using a load-locked |
26 | * store-conditional approach, for example. |
27 | */ |
28 | |
29 | #ifndef ATOMIC_DEC_AND_LOCK |
30 | int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) |
31 | { |
32 | spin_lock(lock); |
33 | if (atomic_dec_and_test(atomic)) |
34 | return 1; |
35 | spin_unlock(lock); |
36 | return 0; |
37 | } |
38 | |
39 | EXPORT_SYMBOL(_atomic_dec_and_lock); |
40 | #endif |