一種簡單的跨平台用戶態自旋鎖

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}