]>
Commit | Line | Data |
---|---|---|
9e84b847 VZ |
1 | ///////////////////////////////////////////////////////////////////////////// |
2 | // Name: include/wx/thrimpl.cpp | |
3 | // Purpose: common part of wxThread Implementations | |
4 | // Author: Vadim Zeitlin | |
5 | // Modified by: | |
6 | // Created: 04.06.02 (extracted from src/*/thread.cpp files) | |
7 | // RCS-ID: $Id$ | |
8 | // Copyright: (c) Vadim Zeitlin (2002) | |
9 | // Licence: wxWindows licence | |
10 | ///////////////////////////////////////////////////////////////////////////// | |
11 | ||
12 | // this file is supposed to be included only by the various thread.cpp | |
13 | ||
14 | // ---------------------------------------------------------------------------- | |
15 | // wxMutex | |
16 | // ---------------------------------------------------------------------------- | |
17 | ||
18 | wxMutex::wxMutex(wxMutexType mutexType) | |
19 | { | |
20 | m_internal = new wxMutexInternal(mutexType); | |
21 | ||
22 | if ( !m_internal->IsOk() ) | |
23 | { | |
24 | delete m_internal; | |
25 | m_internal = NULL; | |
26 | } | |
27 | } | |
28 | ||
29 | wxMutex::~wxMutex() | |
30 | { | |
31 | delete m_internal; | |
32 | } | |
33 | ||
34 | bool wxMutex::IsOk() const | |
35 | { | |
36 | return m_internal != NULL; | |
37 | } | |
38 | ||
39 | wxMutexError wxMutex::Lock() | |
40 | { | |
41 | wxCHECK_MSG( m_internal, wxMUTEX_INVALID, | |
42 | _T("wxMutex::Lock(): not initialized") ); | |
43 | ||
44 | return m_internal->Lock(); | |
45 | } | |
46 | ||
47 | wxMutexError wxMutex::TryLock() | |
48 | { | |
49 | wxCHECK_MSG( m_internal, wxMUTEX_INVALID, | |
50 | _T("wxMutex::TryLock(): not initialized") ); | |
51 | ||
52 | return m_internal->TryLock(); | |
53 | } | |
54 | ||
55 | wxMutexError wxMutex::Unlock() | |
56 | { | |
57 | wxCHECK_MSG( m_internal, wxMUTEX_INVALID, | |
58 | _T("wxMutex::Unlock(): not initialized") ); | |
59 | ||
60 | return m_internal->Unlock(); | |
61 | } | |
62 | ||
d1bab566 SN |
63 | // -------------------------------------------------------------------------- |
64 | // wxConditionInternal | |
65 | // -------------------------------------------------------------------------- | |
66 | ||
67 | #if defined(__WXMSW__) || defined(__WXPM__) | |
68 | // Win32 and OS/2 don't have explicit support for the POSIX condition | |
69 | // variables and their events/event semaphores have quite different semantics, | |
70 | // so we reimplement the conditions from scratch using the mutexes and | |
71 | // semaphores | |
72 | #ifdef __WXPM__ | |
73 | void InterlockedIncrement(LONG *num) | |
74 | { | |
75 | ::DosEnterCritSec(); | |
76 | (*num)++; | |
77 | ::DosExitCritSec(); | |
78 | } | |
79 | #endif | |
80 | ||
81 | class wxConditionInternal | |
82 | { | |
83 | public: | |
84 | wxConditionInternal(wxMutex& mutex); | |
85 | ||
86 | bool IsOk() const { return m_mutex.IsOk() && m_semaphore.IsOk(); } | |
87 | ||
88 | wxCondError Wait(); | |
89 | wxCondError WaitTimeout(unsigned long milliseconds); | |
90 | ||
91 | wxCondError Signal(); | |
92 | wxCondError Broadcast(); | |
93 | ||
94 | private: | |
95 | // the number of threads currently waiting for this condition | |
96 | LONG m_numWaiters; | |
97 | ||
98 | // the critical section protecting m_numWaiters | |
99 | wxCriticalSection m_csWaiters; | |
100 | ||
101 | wxMutex& m_mutex; | |
102 | wxSemaphore m_semaphore; | |
103 | ||
104 | DECLARE_NO_COPY_CLASS(wxConditionInternal) | |
105 | }; | |
106 | ||
107 | wxConditionInternal::wxConditionInternal(wxMutex& mutex) | |
108 | : m_mutex(mutex) | |
109 | { | |
110 | // another thread can't access it until we return from ctor, so no need to | |
111 | // protect access to m_numWaiters here | |
112 | m_numWaiters = 0; | |
113 | } | |
114 | ||
115 | wxCondError wxConditionInternal::Wait() | |
116 | { | |
117 | // increment the number of waiters | |
118 | ::InterlockedIncrement(&m_numWaiters); | |
119 | ||
120 | m_mutex.Unlock(); | |
121 | ||
122 | // a potential race condition can occur here | |
123 | // | |
124 | // after a thread increments nwaiters, and unlocks the mutex and before the | |
125 | // semaphore.Wait() is called, if another thread can cause a signal to be | |
126 | // generated | |
127 | // | |
128 | // this race condition is handled by using a semaphore and incrementing the | |
129 | // semaphore only if 'nwaiters' is greater that zero since the semaphore, | |
130 | // can 'remember' signals the race condition will not occur | |
131 | ||
132 | // wait ( if necessary ) and decrement semaphore | |
133 | wxSemaError err = m_semaphore.Wait(); | |
134 | m_mutex.Lock(); | |
135 | ||
136 | return err == wxSEMA_NO_ERROR ? wxCOND_NO_ERROR : wxCOND_MISC_ERROR; | |
137 | } | |
138 | ||
139 | wxCondError wxConditionInternal::WaitTimeout(unsigned long milliseconds) | |
140 | { | |
141 | ::InterlockedIncrement(&m_numWaiters); | |
142 | ||
143 | m_mutex.Unlock(); | |
144 | ||
145 | // a race condition can occur at this point in the code | |
146 | // | |
147 | // please see the comments in Wait(), for details | |
148 | ||
149 | wxSemaError err = m_semaphore.WaitTimeout(milliseconds); | |
150 | ||
151 | if ( err == wxSEMA_BUSY ) | |
152 | { | |
153 | // another potential race condition exists here it is caused when a | |
154 | // 'waiting' thread timesout, and returns from WaitForSingleObject, but | |
155 | // has not yet decremented 'nwaiters'. | |
156 | // | |
157 | // at this point if another thread calls signal() then the semaphore | |
158 | // will be incremented, but the waiting thread will miss it. | |
159 | // | |
160 | // to handle this particular case, the waiting thread calls | |
161 | // WaitForSingleObject again with a timeout of 0, after locking | |
162 | // 'nwaiters_mutex'. this call does not block because of the zero | |
163 | // timeout, but will allow the waiting thread to catch the missed | |
164 | // signals. | |
165 | wxCriticalSectionLocker lock(m_csWaiters); | |
166 | ||
167 | err = m_semaphore.WaitTimeout(0); | |
168 | ||
169 | if ( err != wxSEMA_NO_ERROR ) | |
170 | { | |
171 | m_numWaiters--; | |
172 | } | |
173 | } | |
174 | ||
175 | m_mutex.Lock(); | |
176 | ||
177 | return err == wxSEMA_NO_ERROR ? wxCOND_NO_ERROR : wxCOND_MISC_ERROR; | |
178 | } | |
179 | ||
180 | wxCondError wxConditionInternal::Signal() | |
181 | { | |
182 | wxCriticalSectionLocker lock(m_csWaiters); | |
183 | ||
184 | if ( m_numWaiters > 0 ) | |
185 | { | |
186 | // increment the semaphore by 1 | |
187 | if ( m_semaphore.Post() != wxSEMA_NO_ERROR ) | |
188 | return wxCOND_MISC_ERROR; | |
189 | ||
190 | m_numWaiters--; | |
191 | } | |
192 | ||
193 | return wxCOND_NO_ERROR; | |
194 | } | |
195 | ||
196 | wxCondError wxConditionInternal::Broadcast() | |
197 | { | |
198 | wxCriticalSectionLocker lock(m_csWaiters); | |
199 | ||
200 | while ( m_numWaiters > 0 ) | |
201 | { | |
202 | if ( m_semaphore.Post() != wxSEMA_NO_ERROR ) | |
203 | return wxCOND_MISC_ERROR; | |
204 | ||
205 | m_numWaiters--; | |
206 | } | |
207 | ||
208 | return wxCOND_NO_ERROR; | |
209 | } | |
210 | #endif | |
211 | ||
9e84b847 VZ |
212 | // ---------------------------------------------------------------------------- |
213 | // wxCondition | |
214 | // ---------------------------------------------------------------------------- | |
215 | ||
216 | wxCondition::wxCondition(wxMutex& mutex) | |
217 | { | |
218 | m_internal = new wxConditionInternal(mutex); | |
219 | ||
220 | if ( !m_internal->IsOk() ) | |
221 | { | |
222 | delete m_internal; | |
223 | m_internal = NULL; | |
224 | } | |
225 | } | |
226 | ||
227 | wxCondition::~wxCondition() | |
228 | { | |
229 | delete m_internal; | |
230 | } | |
231 | ||
232 | bool wxCondition::IsOk() const | |
233 | { | |
234 | return m_internal != NULL; | |
235 | } | |
236 | ||
237 | wxCondError wxCondition::Wait() | |
238 | { | |
239 | wxCHECK_MSG( m_internal, wxCOND_INVALID, | |
240 | _T("wxCondition::Wait(): not initialized") ); | |
241 | ||
242 | return m_internal->Wait(); | |
243 | } | |
244 | ||
245 | wxCondError wxCondition::WaitTimeout(unsigned long milliseconds) | |
246 | { | |
247 | wxCHECK_MSG( m_internal, wxCOND_INVALID, | |
248 | _T("wxCondition::Wait(): not initialized") ); | |
249 | ||
250 | return m_internal->WaitTimeout(milliseconds); | |
251 | } | |
252 | ||
253 | wxCondError wxCondition::Signal() | |
254 | { | |
255 | wxCHECK_MSG( m_internal, wxCOND_INVALID, | |
256 | _T("wxCondition::Signal(): not initialized") ); | |
257 | ||
258 | return m_internal->Signal(); | |
259 | } | |
260 | ||
261 | wxCondError wxCondition::Broadcast() | |
262 | { | |
263 | wxCHECK_MSG( m_internal, wxCOND_INVALID, | |
264 | _T("wxCondition::Broadcast(): not initialized") ); | |
265 | ||
266 | return m_internal->Broadcast(); | |
267 | } | |
268 | ||
269 | // -------------------------------------------------------------------------- | |
270 | // wxSemaphore | |
271 | // -------------------------------------------------------------------------- | |
272 | ||
273 | wxSemaphore::wxSemaphore(int initialcount, int maxcount) | |
274 | { | |
275 | m_internal = new wxSemaphoreInternal( initialcount, maxcount ); | |
276 | if ( !m_internal->IsOk() ) | |
277 | { | |
278 | delete m_internal; | |
279 | m_internal = NULL; | |
280 | } | |
281 | } | |
282 | ||
283 | wxSemaphore::~wxSemaphore() | |
284 | { | |
285 | delete m_internal; | |
286 | } | |
287 | ||
288 | bool wxSemaphore::IsOk() const | |
289 | { | |
290 | return m_internal != NULL; | |
291 | } | |
292 | ||
293 | wxSemaError wxSemaphore::Wait() | |
294 | { | |
295 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, | |
296 | _T("wxSemaphore::Wait(): not initialized") ); | |
297 | ||
298 | return m_internal->Wait(); | |
299 | } | |
300 | ||
301 | wxSemaError wxSemaphore::TryWait() | |
302 | { | |
303 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, | |
304 | _T("wxSemaphore::TryWait(): not initialized") ); | |
305 | ||
306 | return m_internal->TryWait(); | |
307 | } | |
308 | ||
309 | wxSemaError wxSemaphore::WaitTimeout(unsigned long milliseconds) | |
310 | { | |
311 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, | |
312 | _T("wxSemaphore::WaitTimeout(): not initialized") ); | |
313 | ||
314 | return m_internal->WaitTimeout(milliseconds); | |
315 | } | |
316 | ||
317 | wxSemaError wxSemaphore::Post() | |
318 | { | |
319 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, | |
320 | _T("wxSemaphore::Post(): not initialized") ); | |
321 | ||
322 | return m_internal->Post(); | |
323 | } | |
324 |