自旋锁作为一种并发同步的手段，特别适用于竞争少和锁时间短的情况，在驱动及内核代码中经常被用到，本文讲述一种适合用户态程序的自旋锁，支持Windows和Linux（GCC>=4.1.2）平台，并提供了C语言的接口和实现。
接口
spin_trylock如果获取成功返回1，否则返回0；spin_is_lock如果已加锁，返回1，否则返回0。
1
typedef struct
2
{
3
volatile long flag_;
4 volatile long* spin_;
5
}spin_lock_t;
6
7void spin_init(spin_lock_t* lock,long* flag);
8
9void spin_lock(spin_lock_t* lock);
10
11int spin_trylock(spin_lock_t* lock);
12
13void spin_unlock(spin_lock_t* lock);
14
15int spin_is_lock(spin_lock_t* lock);
实现
1
#ifdef _MSC_VER
2#include <windows.h>
3#elif defined(__GNUC__)
4#if __GNUC__<4 || (__GNUC__==4 && __GNUC_MINOR__<1)
5#error GCC version must be greater or equal than 4.1.2
6#endif
7#include <sched.h>
8#else
9#error Currently only windows and linux os are supported
10#endif
11
12void spin_init(spin_lock_t* lock,long* flag)
13
{
14
#ifdef _MSC_VER
15 InterlockedExchange((volatile long*)&lock->flag_,0);
16 InterlockedExchange((volatile long*)&lock->spin_,flag?(long)flag:(long)&lock->flag_);
17#elif defined(__GNUC__)
18 __sync_and_and_fetch((long*)&lock->flag_,0);
19 __sync_lock_test_and_set((long*)&lock->spin_,flag?(long)flag:(long)&lock->flag_);
20#endif
21
}
22
23void spin_lock(spin_lock_t* lock)
24{
25#ifdef _MSC_VER
26 for (;0!=InterlockedExchange((volatile long*)lock->spin_,1);)
27
{
28 Sleep(1);
29
}
30#elif defined(__GNUC__)
31 for (;0!=__sync_fetch_and_or(lock->spin_,1);)
32 {
33 sched_yield();
34 }
35#endif
36}
37
38int spin_trylock(spin_lock_t* lock)
39{
40#ifdef _MSC_VER
41 return !InterlockedExchange((volatile long*)lock->spin_,1);
42#elif defined(__GNUC__)
43 return !__sync_fetch_and_or(lock->spin_,1);
44#endif
45}
46
47void spin_unlock(spin_lock_t* lock)
48{
49#ifdef _MSC_VER
50 InterlockedExchange((volatile long*)lock->spin_,0);
51#elif defined(__GNUC__)
52 __sync_and_and_fetch(lock->spin_,0);
53#endif
54}
55
56int spin_is_lock(spin_lock_t* lock)
57{
58#ifdef _MSC_VER
59 return InterlockedExchangeAdd((volatile long*)lock->spin_,0);
60#elif defined(__GNUC__)
61 return __sync_add_and_fetch(lock->spin_,0);
62#endif
63}
posted on 2012-06-13 21:02
春秋十二月 阅读(3045)
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C/C++