互斥鎖，用來保證任一時(shí)刻只有單個(gè)線程或進(jìn)程擁有對(duì)共享資源的互斥訪問權(quán)，在這里將posix thread中的互斥體、win32中的互斥體和臨界區(qū)，統(tǒng)稱為互斥鎖，其特點(diǎn)如下： ● 范圍：線程鎖和進(jìn)程鎖，前者僅用于同一進(jìn)程內(nèi)多線程間，而后者用于進(jìn)程間，顯然，它也能用于同一進(jìn)程內(nèi)多線程間，但效率較低。posix的互斥體既可以是線程鎖，也可以是進(jìn)程鎖，這由它的一個(gè)屬性決定：pthread_process_shared或pthread_process_private。win32中的臨界區(qū)是一種線程鎖，而互斥體既可以是線程鎖，也可以是進(jìn)程鎖，這由它的一個(gè)名稱決定：createmutex中的第3個(gè)參數(shù)。 ● 類型：posix中的互斥體，包括普通鎖、遞歸鎖、檢測(cè)鎖和適應(yīng)鎖四種；而win32中的臨界區(qū)在同一線程內(nèi)可多次加鎖和解鎖，相當(dāng)于遞歸鎖，而互斥體則相當(dāng)于普通鎖。 ● 操作：包括創(chuàng)建鎖、加鎖、解鎖、檢測(cè)鎖和銷毀鎖5種操作，其中加鎖操作又可分為永久等待和超時(shí)等待2種。對(duì)于win32中的臨界區(qū)，不存在超時(shí)等待的加鎖。
接口
所有鎖操作，成功返回0，失敗posix返回非0的錯(cuò)誤碼，win32返回-1，調(diào)用getlasterror可獲取錯(cuò)誤碼。對(duì)于超時(shí)加鎖，第2個(gè)參數(shù)超時(shí)不是時(shí)間差，而是絕對(duì)到期時(shí)間。對(duì)于win32中的互斥體，廢棄返回1，超時(shí)返回2。
1
#ifdef _POSIX_THREAD
2#include <pthread.h>
3#include <sys/time.h>
4
5typedef pthread_mutex_t mutex_t;
6typedef pthread_mutexattr_t mutexattr_t;
7typedef void SECURITY_ATTRIBUTES;
8
9#elif defined(_WIN32_THREAD)
10#ifndef _WIN32_WINNT
11# define _WIN32_WINNT 0x0501
12#endif
13#include <winsock2.h>
14
15typedef struct
16
{
17
int type_;
18 union
19
{
20 HANDLE proc_lock_;
21 CRITICAL_SECTION thr_lock_;
22
};
23
}mutex_t;
24typedef void mutexattr_t;
25
26#else
27#error Currently only support win32 and posix thread models
28#endif
29
30#define MUTEX_THREAD_SHARED 1
31#define MUTEX_PROCESS_SHARED 2
32
33int mutex_init(mutex_t* m,int scope,int type,const char* name,
34 mutexattr_t* attr,SECURITY_ATTRIBUTES* sa);
35
36int mutex_lock(mutex_t* m);
37
38int mutex_timedlock(mutex_t* m,const struct timeval* val);
39
40int mutex_trylock(mutex_t* m);
41
42int mutex_unlock(mutex_t* m);
43
44int mutex_destroy(mutex_t* m); 實(shí)現(xiàn)
1int mutex_init(mutex_t* m,int scope,int type,const char* name,mutexattr_t* attr,SECURITY_ATTRIBUTES* sa)
2{
3#ifdef _POSIX_THREAD
4 int ret, init = 0;
5 pthread_mutexattr_t tmp;
6 if(0==attr) attr = &tmp;
7 if(attr==&tmp)
8 {
9 ret = pthread_mutexattr_init(attr);
10 if (0==ret) init = 1;
11 }
12 if(0==ret && 0 != scope)
13 {
14#ifdef _POSIX_THREAD_PROCESS_SHARED
15 ret = pthread_mutexattr_setpshared(attr,lock_scope);
16#endif
17 }
18 if(0==ret && 0 != type)
19 {
20#ifdef __USE_UNIX98
21 ret = pthread_mutexattr_settype(attr,lock_type);
22#endif
23 }
24 if (0==ret)
25 ret = pthread_mutex_init(m,attr);
26 if (1==init && attr==&tmp)
27 pthread_mutexattr_destroy(attr);
28 return ret;
29#else
30 m->type_ = scope;
31 switch (m->type_)
32 {
33 case MUTEX_THREAD_SHARED:
34 __try
35 {
36 InitializeCriticalSection(&m->thr_lock_);
37 }
38 __except(EXCEPTION_EXECUTE_HANDLER)
39 {
40 return -1;
41 }
42 return 0;
43
44 case MUTEX_PROCESS_SHARED:
45 m->proc_lock_ = CreateMutexA(sa,FALSE,name);
46 if (0==m->proc_lock_&&ERROR_ACCESS_DENIED==GetLastError())
47 m->proc_lock_ = OpenMutexA(MUTEX_ALL_ACCESS,FALSE,name);
48 if (0==m->proc_lock_)
49 return -1;
50 return 0;
51
52 default: return -1;
53 }
54#endif
55}
56
57int mutex_lock(mutex_t* m)
58{
59#ifdef _POSIX_THREAD
60 return pthread_mutex_lock(m);
61#else
62 switch(m->type_)
63 {
64 case MUTEX_THREAD_SHARED:
65 EnterCriticalSection(&m->thr_lock_);
66 return 0;
67
68 case MUTEX_PROCESS_SHARED:
69 switch (WaitForSingleObject (m->proc_lock_, INFINITE))
70 {
71 case WAIT_OBJECT_0: return 0;
72 case WAIT_ABANDONED: return 1;
73 default: return -1;
74 }
75 break;
76
77 default: return -1;
78 }
79#endif
80}
81
82int mutex_timedlock(mutex_t* m,const struct timeval* val)
83{
84 //val should be an absolute time.
85#ifdef _POSIX_THREAD
86 struct timespec ts = {.tv_sec = val->tv_sec,.tv_nsec=val->tv_usec*1000};
87 return pthread_mutex_timedlock(m,&ts);
88#else
89 switch(m->type_)
90 {
91 // not support CriticalSection,so simply return -1.
92 case MUTEX_THREAD_SHARED:
93 return -1;
94
95 case MUTEX_PROCESS_SHARED:
96 {
97 FILETIME ft;
98 struct timeval cur,diff;
99
100 GetSystemTimeAsFileTime(&ft);
101 cur = FileTime2TimeVal(&ft);
102 diff = timeval_sub(val,&cur);
103
104 switch (WaitForSingleObject (m->proc_lock_, timeval_millsec(&diff)))
105 {
106 case WAIT_OBJECT_0: return 0;
107 case WAIT_ABANDONED: return 1;
108 case WAIT_TIMEOUT: return 2;
109 default: return -1;
110 }
111 }
112 break;
113
114 default: return -1;
115 }
116#endif
117}
118
119int mutex_trylock(mutex_t* m)
120{
121#ifdef _POSIX_THREAD
122 return pthread_mutex_trylock(m);
123#else
124 switch(m->type_)
125 {
126 case MUTEX_THREAD_SHARED:
127 if (!TryEnterCriticalSection(&m->thr_lock_))
128 return -1;
129 return 0;
130
131 case MUTEX_PROCESS_SHARED:
132 switch (WaitForSingleObject (m->proc_lock_, 0))
133 {
134 case WAIT_OBJECT_0: return 0;
135 case WAIT_ABANDONED: return 1;
136 case WAIT_TIMEOUT: return 2;
137 default: return -1;
138 }
139 break;
140
141 default: return -1;
142 }
143#endif
144}
145
146int mutex_unlock(mutex_t* m)
147{
148#ifdef _POSIX_THREAD
149 return pthread_mutex_unlock(m);
150#else
151 switch(m->type_)
152 {
153 case MUTEX_THREAD_SHARED:
154 LeaveCriticalSection(&m->thr_lock_);
155 return 0;
156
157 case MUTEX_PROCESS_SHARED:
158 if (!ReleaseMutex(m->proc_lock_))
159 return -1;
160 return 0;
161
162 default: return -1;
163 }
164#endif
165}
166
167int mutex_destroy(mutex_t* m)
168{
169#ifdef _POSIX_THREAD
170 return pthread_mutex_destroy(m);
171#else
172 switch(m->type_)
173 {
174 case MUTEX_THREAD_SHARED:
175 DeleteCriticalSection(&m->thr_lock_);
176 return 0;
177
178 case MUTEX_PROCESS_SHARED:
179 if (!CloseHandle(m->proc_lock_))
180 return -1;
181 return 0;
182
183 default: return -1;
184 }
185#endif
186}
posted on 2012-06-23 00:08
春秋十二月 閱讀(3611)
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