bool
cThreadLockRw::CheckLock()
{
bool rv = TryWriteLock();
if ( rv )
WriteUnlock();
return rv;
}
/*!
* Acquire the lock for exclusive "write" access. A "writer" thread has
* exclusive ownership of the lock, not shared by any other "reader" or
* "writer" threads.
*/
void WriteLock()
{
if (TryWriteLock())
return;
ATOMIC::EXPONENTIAL_BACKOFF<> backoff;
STATE_PAIR statePair;
bool isWaiting = FALSE; //TRUE, if this writer is on the waiting list
while (TRUE)
{
backoff.Delay();
LoadCurrentState(&statePair);
if (!isWaiting)
{
// Try to acquire the lock right away - without waiting list
//
if (!statePair.ProposeWriteState())
{
// Lock is busy, try to put this writer on the waiting list
//
statePair.ProposeWaitState();
isWaiting = SetState(&statePair);
continue;
}
}
else if (!statePair.ProposeWriteAfterWaitState())
{
// Lock is still busy - leave this writer on the waiting list and Yield
//
OS::Yield();
backoff.Reset(); //Reset backoff delay after Yield
continue;
}
if (SetLockState(&statePair))
return;
}
}
