+ if ( err == wxSEMA_BUSY )
+ {
+ // another potential race condition exists here it is caused when a
+ // 'waiting' thread timesout, and returns from WaitForSingleObject, but
+ // has not yet decremented 'nwaiters'.
+ //
+ // at this point if another thread calls signal() then the semaphore
+ // will be incremented, but the waiting thread will miss it.
+ //
+ // to handle this particular case, the waiting thread calls
+ // WaitForSingleObject again with a timeout of 0, after locking
+ // 'nwaiters_mutex'. this call does not block because of the zero
+ // timeout, but will allow the waiting thread to catch the missed
+ // signals.
+ wxCriticalSectionLocker lock(m_csWaiters);
+
+ err = m_semaphore.WaitTimeout(0);
+
+ if ( err != wxSEMA_NO_ERROR )
+ {
+ m_numWaiters--;
+ }
+ }
+
+ m_mutex.Lock();
+
+ return err == wxSEMA_NO_ERROR ? wxCOND_NO_ERROR : wxCOND_MISC_ERROR;