前言
自旋鎖作為一種並發同步的手段，特別適用於競爭少和鎖時間短的情況，在驅動及內核代碼中經常被用到，本文講述一種適合用戶態程序的自旋鎖，支持WIN32+VC和Linux+GCC(>=4.1.2)平台，並提供了C語言的接口和實現，詳見下文。
接口
1#ifdef __cplusplus
2extern "C" {
3#endif
4
5typedef struct
6{
7 volatile long flag_;
8 volatile long* spin_;
9
10}spin_lock_t;
11
12void spin_init(spin_lock_t* lock,long* flag);
13
14void spin_lock(spin_lock_t* lock);
15
16int spin_trylock(spin_lock_t* lock);
17
18void spin_unlock(spin_lock_t* lock);
19
20int spin_is_lock(spin_lock_t* lock);
21
22#ifdef __cplusplus
23}
24#endif
實現 www.2cto.com 一年十二月 誰主春秋
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}
