/*!
* Attempts to acquire the lock as an exclusive "writer" thread, but
* does not block the caller.
*
* @return Returns TRUE if the lock is acquired, FALSE if not.
*/
bool TryWriteLock()
{
STATE_PAIR statePair;
LoadCurrentState(&statePair);
if (!statePair.ProposeWriteState())
return false;
return SetLockState(&statePair);
}
/*!
* Acquire the lock for "read" access. Multiple "reader" threads may
* simultaneously acquire the lock.
*/
void ReadLock()
{
if (TryReadLock())
return;
ATOMIC::EXPONENTIAL_BACKOFF<> backoff;
STATE_PAIR statePair;
while (TRUE)
{
backoff.Delay();
LoadCurrentState(&statePair);
if (!statePair.ProposeReadState())
{
OS::Yield();
backoff.Reset(); //Reset backoff delay after Yield
continue;
}
if (SetLockState(&statePair))
return;
}
}
/*!
* 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;
}
}
void CCI_GripperActuator::Unlock() {
SetLockState(0.0f);
}
void CCI_GripperActuator::Lock() {
SetLockState(1.0f);
}
