| Bonita Montero <Bonita.Montero@gmail.com>: May 22 07:19PM +0200 I've written a very efficient condvar-implementation for Win32. Here it is: http://pastebin.com/fdjHx9ec I'm pretty sure it's considerably more efficient than the condvars in Win32 since Vista and Windows Server 2008. But I had a strange phnomenon when a thread holding the condvar locked is singalling a waiting thread and after this is sleeping before it is releasing the lock. I extracted the problem in a simple programm without this kind of efficient locking through atomic variables, but just with an event and a semaphore. Here it is: #include <windows.h> #include <stdio.h> HANDLE hEvt, hSema; bool volatile fReleased = false; DWORD WINAPI LockAndReleaseThread( LPVOID lpvThreadParam ); int main() { int const NTHREADS = 2; HANDLE ahWait[2]; ahWait[0] = ::hEvt = CreateEvent( NULL, FALSE, TRUE, NULL ); ahWait[1] = ::hSema = CreateSemaphore( NULL, 0, 1, NULL ); for( int i = 0; i < NTHREADS; i++ ) CreateThread( NULL, 0, LockAndReleaseThread, NULL, 0, NULL ); for( ; ; ) { WaitForMultipleObjects( 2, ahWait, TRUE, INFINITE ); printf( "main thread is holding lock and received signal\n" ); ::fReleased = false; SetEvent( hEvt ); } return 0; } DWORD WINAPI LockAndReleaseThread( LPVOID lpvThreadParam ) { for( ; ; ) { WaitForSingleObject( hEvt, INFINITE ); printf( "spawned thread is holding lock\n" ); if( !::fReleased ) ReleaseSemaphore( ::hSema, 1, NULL ), ::fReleased = true; Sleep( 1000 ); SetEvent( hEvt ); } return 0; } The strange thing here is, that whith my Windows 10 computer, WaitForMultipleObjects in the main-thread never awakens! When I set NTHREADS to 1, the main-thread gets a chance, but beyond it will freeze. Has anyone an explanation for that? Thanks in advance, Bonita Montero -- http://facebook.com/bonita.montero/ --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. https://www.avast.com/antivirus |
| Bonita Montero <Bonita.Montero@gmail.com>: May 23 12:55PM +0200 I've got a solution for this problem. In the main-thread, simply wait for the semaphore and then for the event (in this order - or you're gonna deadlock) with WaitForSingle Object. That's not so efficitent, but works. int main() { int const NTHREADS = 2; HANDLE ahWait[2]; ::hEvt = CreateEvent( NULL, FALSE, TRUE, NULL ); ::hSema = CreateSemaphore( NULL, 0, 1, NULL ); fReleased = false; for( int i = 0; i < NTHREADS; i++ ) CreateThread( NULL, 0, LockAndReleaseThread, NULL, 0, NULL ); for( ; ; ) WaitForSingleObject( ::hSema, INFINITE ), WaitForSingleObject( ::hEvt, INFINITE), printf( "main thread is holding lock and received signal\n" ), ::fReleased = false, SetEvent( ::hEvt ); return 0; } -- http://facebook.com/bonita.montero/ --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. https://www.avast.com/antivirus |
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