/** Attempt to upgrade a share lock that we hold to an exclusive lock. */
private boolean tryUpgradeToExclusiveWithShareLockHeld(
Locks.ResourceType resourceType,
ConcurrentMap<Long, ForsetiLockManager.Lock> lockMap,
long resourceId,
SharedLock sharedLock,
int tries)
throws AcquireLockTimeoutException {
if (sharedLock.tryAcquireUpdateLock(this)) {
try {
// Now we just wait for all clients to release the the share lock
while (sharedLock.numberOfHolders() > 1) {
waitStrategies[resourceType.typeId()].apply(tries++);
markAsWaitingFor(sharedLock, resourceType, resourceId);
}
// No more people other than us holding this lock. Swap it to exclusive
// TODO Wait, why do we need to do this? An update lock with zero shared holders is an
// TODO exclusive lock, no? Why is it not enough to just atomically raise the update bit,
// TODO and then wait for all the shared holders to relinquish their grasp?
lockMap.put(resourceId, myExclusiveLock);
return true;
} catch (DeadlockDetectedException e) {
sharedLock.releaseUpdateLock(this);
throw e;
} catch (Throwable e) {
sharedLock.releaseUpdateLock(this);
clearWaitList();
throw new RuntimeException(e);
}
}
return false;
}
@Override
public boolean tryExclusiveLock(Locks.ResourceType resourceType, long... resourceIds) {
ConcurrentMap<Long, ForsetiLockManager.Lock> lockMap = lockMaps[resourceType.typeId()];
Map<Long, Integer> heldLocks = exclusiveLockCounts[resourceType.typeId()];
for (long resourceId : resourceIds) {
Integer heldCount = heldLocks.get(resourceId);
if (heldCount != null) {
// We already have a lock on this, just increment our local reference counter.
heldLocks.put(resourceId, heldCount + 1);
continue;
}
// Grab the global lock
ForsetiLockManager.Lock lock;
if ((lock = lockMap.putIfAbsent(resourceId, myExclusiveLock)) != null) {
if (lock instanceof SharedLock
&& sharedLockCounts[resourceType.typeId()].containsKey(resourceId)) {
SharedLock sharedLock = (SharedLock) lock;
if (sharedLock.tryAcquireUpdateLock(this)) {
if (sharedLock.numberOfHolders() == 1) {
lockMap.put(resourceId, myExclusiveLock);
return true;
} else {
sharedLock.releaseUpdateLock(this);
return false;
}
}
}
return false;
}
heldLocks.put(resourceId, 1);
}
return true;
}