/** 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;
}
/**
* Attempt to upgrade a share lock to an exclusive lock, grabbing the share lock if we don't hold
* it.
*/
private boolean tryUpgradeSharedToExclusive(
Locks.ResourceType resourceType,
ConcurrentMap<Long, ForsetiLockManager.Lock> lockMap,
long resourceId,
SharedLock sharedLock)
throws AcquireLockTimeoutException {
int tries = 0;
if (!sharedLockCounts[resourceType.typeId()].containsKey(resourceId)) {
// We don't hold the shared lock, we need to grab it to upgrade it to an exclusive one
if (!sharedLock.acquire(this)) {
return false;
}
try {
if (tryUpgradeToExclusiveWithShareLockHeld(
resourceType, lockMap, resourceId, sharedLock, tries)) {
return true;
} else {
releaseGlobalLock(lockMap, resourceId);
return false;
}
} catch (Throwable e) {
releaseGlobalLock(lockMap, resourceId);
throw e;
}
} else {
// We do hold the shared lock, so no reason to deal with the complexity in the case above.
return tryUpgradeToExclusiveWithShareLockHeld(
resourceType, lockMap, resourceId, sharedLock, tries);
}
}
/**
* Atomically increment a counter in the ControllerBB sharedMap.
*
* @param keyBase A string from ControllerBB that prefixes a vm id to use as a key in the
* ControllerBB shared map. The VM id used is the current vm's id.
*/
public static void incMapCounter(String keyBase) {
String key = keyBase + RemoteTestModule.getMyVmid();
Log.getLogWriter().info("Incrementing sharedMap counter " + key);
SharedLock slock = ControllerBB.getBB().getSharedLock();
slock.lock();
try {
int newValue = 0;
Object value = ControllerBB.getBB().getSharedMap().get(key);
if (value == null) {
newValue = 1;
} else {
newValue = ((Integer) value).intValue() + 1;
}
ControllerBB.getBB().getSharedMap().put(key, new Integer(newValue));
Log.getLogWriter().info("Incremented sharedMap counter, count is now " + newValue);
} finally {
slock.unlock();
}
}
@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;
}
