| 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 | |
| 63 | // -------------------------------------------------------------------------- |
| 64 | // wxConditionInternal |
| 65 | // -------------------------------------------------------------------------- |
| 66 | |
| 67 | // Win32 and OS/2 don't have explicit support for the POSIX condition |
| 68 | // variables and their events/event semaphores have quite different semantics, |
| 69 | // so we reimplement the conditions from scratch using the mutexes and |
| 70 | // semaphores |
| 71 | #if defined(__WXMSW__) || defined(__OS2__) || defined(__EMX__) |
| 72 | |
| 73 | class wxConditionInternal |
| 74 | { |
| 75 | public: |
| 76 | wxConditionInternal(wxMutex& mutex); |
| 77 | |
| 78 | bool IsOk() const { return m_mutex.IsOk() && m_semaphore.IsOk(); } |
| 79 | |
| 80 | wxCondError Wait(); |
| 81 | wxCondError WaitTimeout(unsigned long milliseconds); |
| 82 | |
| 83 | wxCondError Signal(); |
| 84 | wxCondError Broadcast(); |
| 85 | |
| 86 | private: |
| 87 | // the number of threads currently waiting for this condition |
| 88 | LONG m_numWaiters; |
| 89 | |
| 90 | // the critical section protecting m_numWaiters |
| 91 | wxCriticalSection m_csWaiters; |
| 92 | |
| 93 | wxMutex& m_mutex; |
| 94 | wxSemaphore m_semaphore; |
| 95 | |
| 96 | DECLARE_NO_COPY_CLASS(wxConditionInternal) |
| 97 | }; |
| 98 | |
| 99 | wxConditionInternal::wxConditionInternal(wxMutex& mutex) |
| 100 | : m_mutex(mutex) |
| 101 | { |
| 102 | // another thread can't access it until we return from ctor, so no need to |
| 103 | // protect access to m_numWaiters here |
| 104 | m_numWaiters = 0; |
| 105 | } |
| 106 | |
| 107 | wxCondError wxConditionInternal::Wait() |
| 108 | { |
| 109 | // increment the number of waiters |
| 110 | { |
| 111 | wxCriticalSectionLocker lock(m_csWaiters); |
| 112 | m_numWaiters++; |
| 113 | } |
| 114 | |
| 115 | m_mutex.Unlock(); |
| 116 | |
| 117 | // a potential race condition can occur here |
| 118 | // |
| 119 | // after a thread increments m_numWaiters, and unlocks the mutex and before |
| 120 | // the semaphore.Wait() is called, if another thread can cause a signal to |
| 121 | // be generated |
| 122 | // |
| 123 | // this race condition is handled by using a semaphore and incrementing the |
| 124 | // semaphore only if m_numWaiters is greater that zero since the semaphore, |
| 125 | // can 'remember' signals the race condition will not occur |
| 126 | |
| 127 | // wait ( if necessary ) and decrement semaphore |
| 128 | wxSemaError err = m_semaphore.Wait(); |
| 129 | m_mutex.Lock(); |
| 130 | |
| 131 | if ( err == wxSEMA_NO_ERROR ) |
| 132 | return wxCOND_NO_ERROR; |
| 133 | else if ( err == wxSEMA_TIMEOUT ) |
| 134 | return wxCOND_TIMEOUT; |
| 135 | else |
| 136 | return wxCOND_MISC_ERROR; |
| 137 | } |
| 138 | |
| 139 | wxCondError wxConditionInternal::WaitTimeout(unsigned long milliseconds) |
| 140 | { |
| 141 | { |
| 142 | wxCriticalSectionLocker lock(m_csWaiters); |
| 143 | m_numWaiters++; |
| 144 | } |
| 145 | |
| 146 | m_mutex.Unlock(); |
| 147 | |
| 148 | // a race condition can occur at this point in the code |
| 149 | // |
| 150 | // please see the comments in Wait(), for details |
| 151 | |
| 152 | wxSemaError err = m_semaphore.WaitTimeout(milliseconds); |
| 153 | |
| 154 | if ( err == wxSEMA_TIMEOUT ) |
| 155 | { |
| 156 | // another potential race condition exists here it is caused when a |
| 157 | // 'waiting' thread times out, and returns from WaitForSingleObject, |
| 158 | // but has not yet decremented m_numWaiters |
| 159 | // |
| 160 | // at this point if another thread calls signal() then the semaphore |
| 161 | // will be incremented, but the waiting thread will miss it. |
| 162 | // |
| 163 | // to handle this particular case, the waiting thread calls |
| 164 | // WaitForSingleObject again with a timeout of 0, after locking |
| 165 | // m_csWaiters. This call does not block because of the zero |
| 166 | // timeout, but will allow the waiting thread to catch the missed |
| 167 | // signals. |
| 168 | wxCriticalSectionLocker lock(m_csWaiters); |
| 169 | |
| 170 | wxSemaError err2 = m_semaphore.WaitTimeout(0); |
| 171 | |
| 172 | if ( err2 != wxSEMA_NO_ERROR ) |
| 173 | { |
| 174 | m_numWaiters--; |
| 175 | } |
| 176 | } |
| 177 | |
| 178 | m_mutex.Lock(); |
| 179 | |
| 180 | return err == wxSEMA_NO_ERROR ? wxCOND_NO_ERROR |
| 181 | : err == wxSEMA_TIMEOUT ? wxCOND_TIMEOUT |
| 182 | : wxCOND_MISC_ERROR; |
| 183 | } |
| 184 | |
| 185 | wxCondError wxConditionInternal::Signal() |
| 186 | { |
| 187 | wxCriticalSectionLocker lock(m_csWaiters); |
| 188 | |
| 189 | if ( m_numWaiters > 0 ) |
| 190 | { |
| 191 | // increment the semaphore by 1 |
| 192 | if ( m_semaphore.Post() != wxSEMA_NO_ERROR ) |
| 193 | return wxCOND_MISC_ERROR; |
| 194 | |
| 195 | m_numWaiters--; |
| 196 | } |
| 197 | |
| 198 | return wxCOND_NO_ERROR; |
| 199 | } |
| 200 | |
| 201 | wxCondError wxConditionInternal::Broadcast() |
| 202 | { |
| 203 | wxCriticalSectionLocker lock(m_csWaiters); |
| 204 | |
| 205 | while ( m_numWaiters > 0 ) |
| 206 | { |
| 207 | if ( m_semaphore.Post() != wxSEMA_NO_ERROR ) |
| 208 | return wxCOND_MISC_ERROR; |
| 209 | |
| 210 | m_numWaiters--; |
| 211 | } |
| 212 | |
| 213 | return wxCOND_NO_ERROR; |
| 214 | } |
| 215 | |
| 216 | #endif // MSW or OS2 |
| 217 | |
| 218 | // ---------------------------------------------------------------------------- |
| 219 | // wxCondition |
| 220 | // ---------------------------------------------------------------------------- |
| 221 | |
| 222 | wxCondition::wxCondition(wxMutex& mutex) |
| 223 | { |
| 224 | m_internal = new wxConditionInternal(mutex); |
| 225 | |
| 226 | if ( !m_internal->IsOk() ) |
| 227 | { |
| 228 | delete m_internal; |
| 229 | m_internal = NULL; |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | wxCondition::~wxCondition() |
| 234 | { |
| 235 | delete m_internal; |
| 236 | } |
| 237 | |
| 238 | bool wxCondition::IsOk() const |
| 239 | { |
| 240 | return m_internal != NULL; |
| 241 | } |
| 242 | |
| 243 | wxCondError wxCondition::Wait() |
| 244 | { |
| 245 | wxCHECK_MSG( m_internal, wxCOND_INVALID, |
| 246 | _T("wxCondition::Wait(): not initialized") ); |
| 247 | |
| 248 | return m_internal->Wait(); |
| 249 | } |
| 250 | |
| 251 | wxCondError wxCondition::WaitTimeout(unsigned long milliseconds) |
| 252 | { |
| 253 | wxCHECK_MSG( m_internal, wxCOND_INVALID, |
| 254 | _T("wxCondition::Wait(): not initialized") ); |
| 255 | |
| 256 | return m_internal->WaitTimeout(milliseconds); |
| 257 | } |
| 258 | |
| 259 | wxCondError wxCondition::Signal() |
| 260 | { |
| 261 | wxCHECK_MSG( m_internal, wxCOND_INVALID, |
| 262 | _T("wxCondition::Signal(): not initialized") ); |
| 263 | |
| 264 | return m_internal->Signal(); |
| 265 | } |
| 266 | |
| 267 | wxCondError wxCondition::Broadcast() |
| 268 | { |
| 269 | wxCHECK_MSG( m_internal, wxCOND_INVALID, |
| 270 | _T("wxCondition::Broadcast(): not initialized") ); |
| 271 | |
| 272 | return m_internal->Broadcast(); |
| 273 | } |
| 274 | |
| 275 | // -------------------------------------------------------------------------- |
| 276 | // wxSemaphore |
| 277 | // -------------------------------------------------------------------------- |
| 278 | |
| 279 | wxSemaphore::wxSemaphore(int initialcount, int maxcount) |
| 280 | { |
| 281 | m_internal = new wxSemaphoreInternal( initialcount, maxcount ); |
| 282 | if ( !m_internal->IsOk() ) |
| 283 | { |
| 284 | delete m_internal; |
| 285 | m_internal = NULL; |
| 286 | } |
| 287 | } |
| 288 | |
| 289 | wxSemaphore::~wxSemaphore() |
| 290 | { |
| 291 | delete m_internal; |
| 292 | } |
| 293 | |
| 294 | bool wxSemaphore::IsOk() const |
| 295 | { |
| 296 | return m_internal != NULL; |
| 297 | } |
| 298 | |
| 299 | wxSemaError wxSemaphore::Wait() |
| 300 | { |
| 301 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, |
| 302 | _T("wxSemaphore::Wait(): not initialized") ); |
| 303 | |
| 304 | return m_internal->Wait(); |
| 305 | } |
| 306 | |
| 307 | wxSemaError wxSemaphore::TryWait() |
| 308 | { |
| 309 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, |
| 310 | _T("wxSemaphore::TryWait(): not initialized") ); |
| 311 | |
| 312 | return m_internal->TryWait(); |
| 313 | } |
| 314 | |
| 315 | wxSemaError wxSemaphore::WaitTimeout(unsigned long milliseconds) |
| 316 | { |
| 317 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, |
| 318 | _T("wxSemaphore::WaitTimeout(): not initialized") ); |
| 319 | |
| 320 | return m_internal->WaitTimeout(milliseconds); |
| 321 | } |
| 322 | |
| 323 | wxSemaError wxSemaphore::Post() |
| 324 | { |
| 325 | wxCHECK_MSG( m_internal, wxSEMA_INVALID, |
| 326 | _T("wxSemaphore::Post(): not initialized") ); |
| 327 | |
| 328 | return m_internal->Post(); |
| 329 | } |
| 330 | |