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Fix race condition.

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Work around undocumented SignalObjectAndWait behavior; the docs
refer to "the object", but the function takes two objects.  (Cut and paste
documentation ...)
This commit is contained in:
Glenn Maynard
2005-01-29 20:25:52 +00:00
parent b3ff1f0119
commit 46f414e7e5
1 changed files with 10 additions and 1 deletions
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stepmania/src/arch/Threads/Threads_Win32.cpp
+10 -1
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@@ -282,7 +282,8 @@ EventImpl_Win32::~EventImpl_Win32()
static bool PortableSignalObjectAndWait( HANDLE hObjectToSignal, HANDLE hObjectToWaitOn, bool bFirstParamIsMutex, unsigned iMilliseconds = INFINITE ) static bool PortableSignalObjectAndWait( HANDLE hObjectToSignal, HANDLE hObjectToWaitOn, bool bFirstParamIsMutex, unsigned iMilliseconds = INFINITE )
{ {
static bool bSignalObjectAndWaitUnavailable = false; static bool bSignalObjectAndWaitUnavailable = false;
if( !bSignalObjectAndWaitUnavailable ) /* Watch out: SignalObjectAndWait doesn't work when iMilliseconds is zero. */
if( !bSignalObjectAndWaitUnavailable && iMilliseconds != 0 )
{ {
DWORD ret = SignalObjectAndWait( hObjectToSignal, hObjectToWaitOn, iMilliseconds, false ); DWORD ret = SignalObjectAndWait( hObjectToSignal, hObjectToWaitOn, iMilliseconds, false );
switch( ret ) switch( ret )
@@ -358,6 +359,14 @@ bool EventImpl_Win32::Wait( RageTimer *pTimeout )
bool bSuccess = PortableSignalObjectAndWait( m_pParent->mutex, m_WakeupSema, true, iMilliseconds ); bool bSuccess = PortableSignalObjectAndWait( m_pParent->mutex, m_WakeupSema, true, iMilliseconds );
EnterCriticalSection( &m_iNumWaitingLock ); EnterCriticalSection( &m_iNumWaitingLock );
if( !bSuccess )
{
/* Avoid a race condition: someone may have signalled the object between PortableSignalObjectAndWait
* and EnterCriticalSection. While we hold m_iNumWaitingLock, poll (with a zero timeout) the
* object one last time. */
if( WaitForSingleObject( m_WakeupSema, 0 ) == WAIT_OBJECT_0 )
bSuccess = true;
}
--m_iNumWaiting; --m_iNumWaiting;
bool bLastWaiting = m_iNumWaiting == 0; bool bLastWaiting = m_iNumWaiting == 0;
LeaveCriticalSection( &m_iNumWaitingLock ); LeaveCriticalSection( &m_iNumWaitingLock );