bool LockerImpl::saveLockStateAndUnlock(Locker::LockSnapshot* stateOut) {
// We shouldn't be saving and restoring lock state from inside a WriteUnitOfWork.
invariant(!inAWriteUnitOfWork());
// Clear out whatever is in stateOut.
stateOut->locks.clear();
stateOut->globalMode = MODE_NONE;
// First, we look at the global lock. There is special handling for this (as the flush
// lock goes along with it) so we store it separately from the more pedestrian locks.
LockRequestsMap::Iterator globalRequest = _requests.find(resourceIdGlobal);
if (!globalRequest) {
// If there's no global lock there isn't really anything to do. Check that.
for (auto it = _requests.begin(); !it.finished(); it.next()) {
invariant(it.key().getType() == RESOURCE_MUTEX);
}
return false;
}
// If the global lock or RSTL has been acquired more than once, we're probably somewhere in a
// DBDirectClient call. It's not safe to release and reacquire locks -- the context using
// the DBDirectClient is probably not prepared for lock release.
LockRequestsMap::Iterator rstlRequest =
_requests.find(resourceIdReplicationStateTransitionLock);
if (globalRequest->recursiveCount > 1 || (rstlRequest && rstlRequest->recursiveCount > 1)) {
return false;
}
// The global lock must have been acquired just once
stateOut->globalMode = globalRequest->mode;
invariant(unlock(resourceIdGlobal));
// Next, the non-global locks.
for (LockRequestsMap::Iterator it = _requests.begin(); !it.finished(); it.next()) {
const ResourceId resId = it.key();
const ResourceType resType = resId.getType();
if (resType == RESOURCE_MUTEX)
continue;
// We should never have to save and restore metadata locks.
invariant(RESOURCE_DATABASE == resId.getType() || RESOURCE_COLLECTION == resId.getType() ||
(RESOURCE_GLOBAL == resId.getType() && isSharedLockMode(it->mode)) ||
(resourceIdReplicationStateTransitionLock == resId && it->mode == MODE_IX));
// And, stuff the info into the out parameter.
OneLock info;
info.resourceId = resId;
info.mode = it->mode;
stateOut->locks.push_back(info);
invariant(unlock(resId));
}
invariant(!isLocked());
// Sort locks by ResourceId. They'll later be acquired in this canonical locking order.
std::sort(stateOut->locks.begin(), stateOut->locks.end());
return true;
}
bool LockerImpl<IsForMMAPV1>::_shouldDelayUnlock(ResourceId resId, LockMode mode) const {
switch (resId.getType()) {
// The flush lock must not participate in two-phase locking because we need to temporarily
// yield it while blocked waiting to acquire other locks.
case RESOURCE_MMAPV1_FLUSH:
case RESOURCE_MUTEX:
return false;
case RESOURCE_GLOBAL:
case RESOURCE_DATABASE:
case RESOURCE_COLLECTION:
case RESOURCE_METADATA:
break;
default:
MONGO_UNREACHABLE;
}
switch (mode) {
case MODE_X:
case MODE_IX:
return true;
case MODE_IS:
case MODE_S:
return _sharedLocksShouldTwoPhaseLock;
default:
MONGO_UNREACHABLE;
}
}
LockResult LockerImpl<IsForMMAPV1>::lockBegin(OperationContext* opCtx,
ResourceId resId,
LockMode mode) {
dassert(!getWaitingResource().isValid());
LockRequest* request;
bool isNew = true;
LockRequestsMap::Iterator it = _requests.find(resId);
if (!it) {
scoped_spinlock scopedLock(_lock);
LockRequestsMap::Iterator itNew = _requests.insert(resId);
itNew->initNew(this, &_notify);
request = itNew.objAddr();
} else {
request = it.objAddr();
isNew = false;
}
// If unlockPending is nonzero, that means a LockRequest already exists for this resource but
// is planned to be released at the end of this WUOW due to two-phase locking. Rather than
// unlocking the existing request, we can reuse it if the existing mode matches the new mode.
if (request->unlockPending && isModeCovered(mode, request->mode)) {
request->unlockPending--;
if (!request->unlockPending) {
_numResourcesToUnlockAtEndUnitOfWork--;
}
return LOCK_OK;
}
// Making this call here will record lock re-acquisitions and conversions as well.
globalStats.recordAcquisition(_id, resId, mode);
_stats.recordAcquisition(resId, mode);
// Give priority to the full modes for global, parallel batch writer mode,
// and flush lock so we don't stall global operations such as shutdown or flush.
const ResourceType resType = resId.getType();
if (resType == RESOURCE_GLOBAL || (IsForMMAPV1 && resId == resourceIdMMAPV1Flush)) {
if (mode == MODE_S || mode == MODE_X) {
request->enqueueAtFront = true;
request->compatibleFirst = true;
}
} else if (resType != RESOURCE_MUTEX) {
// This is all sanity checks that the global and flush locks are always be acquired
// before any other lock has been acquired and they must be in sync with the nesting.
DEV {
const LockRequestsMap::Iterator itGlobal = _requests.find(resourceIdGlobal);
invariant(itGlobal->recursiveCount > 0);
invariant(itGlobal->mode != MODE_NONE);
// Check the MMAP V1 flush lock is held in the appropriate mode
invariant(!IsForMMAPV1 ||
isLockHeldForMode(resourceIdMMAPV1Flush, _getModeForMMAPV1FlushLock()));
};
}
Resource FileResourceLoader::get(const ResourceId &id)
{
if (id.getType() & "File")
{
fs::path p((m_basePath / id.getName()).native_directory_string());
if (fs::exists(p))
{
FileData *pData = new FileData(this);
pData->setId(id);
pData->setPath(p);
return FileResource(pData);
}
}
return Resource();
}
reg_t kLock(EngineState *s, int argc, reg_t *argv) {
int state = argc > 2 ? argv[2].toUint16() : 1;
ResourceType type = g_sci->getResMan()->convertResType(argv[0].toUint16());
ResourceId id = ResourceId(type, argv[1].toUint16());
Resource *which;
switch (state) {
case 1 :
g_sci->getResMan()->findResource(id, 1);
break;
case 0 :
if (id.getNumber() == 0xFFFF) {
// Unlock all resources of the requested type
Common::List<ResourceId> *resources = g_sci->getResMan()->listResources(type);
Common::List<ResourceId>::iterator itr = resources->begin();
while (itr != resources->end()) {
Resource *res = g_sci->getResMan()->testResource(*itr);
if (res->isLocked())
g_sci->getResMan()->unlockResource(res);
++itr;
}
delete resources;
} else {
which = g_sci->getResMan()->findResource(id, 0);
if (which)
g_sci->getResMan()->unlockResource(which);
else {
if (id.getType() == kResourceTypeInvalid)
warning("[resMan] Attempt to unlock resource %i of invalid type %i", id.getNumber(), argv[0].toUint16());
else
// Happens in CD games (e.g. LSL6CD) with the message
// resource. It isn't fatal, and it's usually caused
// by leftover scripts.
debugC(kDebugLevelResMan, "[resMan] Attempt to unlock non-existant resource %s", id.toString().c_str());
}
}
break;
}
return s->r_acc;
}
LockResult LockerImpl<IsForMMAPV1>::lockBegin(ResourceId resId, LockMode mode) {
dassert(!getWaitingResource().isValid());
LockRequest* request;
bool isNew = true;
LockRequestsMap::Iterator it = _requests.find(resId);
if (!it) {
scoped_spinlock scopedLock(_lock);
LockRequestsMap::Iterator itNew = _requests.insert(resId);
itNew->initNew(this, &_notify);
request = itNew.objAddr();
} else {
request = it.objAddr();
isNew = false;
}
// Making this call here will record lock re-acquisitions and conversions as well.
globalStats.recordAcquisition(_id, resId, mode);
_stats.recordAcquisition(resId, mode);
// Give priority to the full modes for global, parallel batch writer mode,
// and flush lock so we don't stall global operations such as shutdown or flush.
const ResourceType resType = resId.getType();
if (resType == RESOURCE_GLOBAL || (IsForMMAPV1 && resId == resourceIdMMAPV1Flush)) {
if (mode == MODE_S || mode == MODE_X) {
request->enqueueAtFront = true;
request->compatibleFirst = true;
}
} else if (resType != RESOURCE_MUTEX) {
// This is all sanity checks that the global and flush locks are always be acquired
// before any other lock has been acquired and they must be in sync with the nesting.
DEV {
const LockRequestsMap::Iterator itGlobal = _requests.find(resourceIdGlobal);
invariant(itGlobal->recursiveCount > 0);
invariant(itGlobal->mode != MODE_NONE);
// Check the MMAP V1 flush lock is held in the appropriate mode
invariant(!IsForMMAPV1 ||
isLockHeldForMode(resourceIdMMAPV1Flush, _getModeForMMAPV1FlushLock()));
};
}
std::string Lock::ResourceMutex::getName(ResourceId resourceId) {
invariant(resourceId.getType() == RESOURCE_MUTEX);
return ResourceIdFactory::nameForId(resourceId);
}
reg_t kLock(EngineState *s, int argc, reg_t *argv) {
// NOTE: In SSCI, kLock uses a boolean lock flag, not a lock counter.
// ScummVM's current counter-based implementation should be better than SSCI
// at dealing with game scripts that unintentionally lock & unlock the same
// resource multiple times (e.g. through recursion), but it will introduce
// memory bugs (resource leaks lasting until the engine is restarted, or
// destruction of kernel locks that lead to a use-after-free) that are
// masked by ResourceManager's LRU cache if scripts rely on kLock being
// idempotent like it was in SSCI.
//
// Like SSCI, resource locks are not persisted in save games in ScummVM
// until GK2, so it is also possible that kLock bugs will appear only after
// restoring a save game.
//
// See also kUnLoad.
ResourceType type = g_sci->getResMan()->convertResType(argv[0].toUint16());
if (type == kResourceTypeSound && getSciVersion() >= SCI_VERSION_1_1) {
type = g_sci->_soundCmd->getSoundResourceType(argv[1].toUint16());
}
const ResourceId id(type, argv[1].toUint16());
const bool lock = argc > 2 ? argv[2].toUint16() : true;
#ifdef ENABLE_SCI32
// SSCI GK2+SCI3 also saves lock states for View, Pic, and Sync resources,
// but so far it seems like audio resources are the only ones that actually
// need to be handled
if (g_sci->_features->hasSci3Audio() && type == kResourceTypeAudio) {
g_sci->_audio32->lockResource(id, lock);
return s->r_acc;
}
#endif
if (getSciVersion() == SCI_VERSION_1_1 &&
(type == kResourceTypeAudio36 || type == kResourceTypeSync36)) {
return s->r_acc;
}
if (lock) {
g_sci->getResMan()->findResource(id, true);
} else {
if (getSciVersion() < SCI_VERSION_2 && id.getNumber() == 0xFFFF) {
// Unlock all resources of the requested type
Common::List<ResourceId> resources = g_sci->getResMan()->listResources(type);
Common::List<ResourceId>::iterator itr;
for (itr = resources.begin(); itr != resources.end(); ++itr) {
Resource *res = g_sci->getResMan()->testResource(*itr);
if (res->isLocked())
g_sci->getResMan()->unlockResource(res);
}
} else {
Resource *which = g_sci->getResMan()->findResource(id, false);
if (which)
g_sci->getResMan()->unlockResource(which);
else {
if (id.getType() == kResourceTypeInvalid)
warning("[resMan] Attempt to unlock resource %i of invalid type %i", id.getNumber(), argv[0].toUint16());
else
// Happens in CD games (e.g. LSL6CD) with the message
// resource. It isn't fatal, and it's usually caused
// by leftover scripts.
debugC(kDebugLevelResMan, "[resMan] Attempt to unlock non-existent resource %s", id.toString().c_str());
}
}
}
return s->r_acc;
}
LockResult LockManager::lock(const ResourceId& resId, LockRequest* request, LockMode mode) {
dassert(mode > MODE_NONE);
// Fast path for acquiring the same lock multiple times in modes, which are already covered
// by the current mode. It is safe to do this without locking, because 1) all calls for the
// same lock request must be done on the same thread and 2) if there are lock requests
// hanging off a given LockHead, then this lock will never disappear.
if ((LockConflictsTable[request->mode] | LockConflictsTable[mode]) ==
LockConflictsTable[request->mode]) {
request->recursiveCount++;
return LOCK_OK;
}
// TODO: For the time being we do not need conversions between unrelated lock modes (i.e.,
// modes which both add and remove to the conflicts set), so these are not implemented yet
// (e.g., S -> IX).
invariant((LockConflictsTable[request->mode] | LockConflictsTable[mode]) ==
LockConflictsTable[mode]);
LockBucket* bucket = _getBucket(resId);
scoped_spinlock scopedLock(bucket->mutex);
LockHead* lock;
LockHeadMap::iterator it = bucket->data.find(resId);
if (it == bucket->data.end()) {
// Lock is free (not on the map)
invariant(request->status == LockRequest::STATUS_NEW);
lock = new LockHead(resId);
bucket->data.insert(LockHeadPair(resId, lock));
}
else {
// Lock is not free
lock = it->second;
}
// Sanity check if requests are being reused
invariant(request->lock == NULL || request->lock == lock);
request->lock = lock;
request->recursiveCount++;
if (request->status == LockRequest::STATUS_NEW) {
invariant(request->recursiveCount == 1);
// The flush lock must be FIFO ordered or else we will starve the dur threads and not
// block new writers. This means that if anyone is blocking on a mustFIFO resource we
// must get in line, even if we don't conflict with the grantedModes and could take the
// lock immediately.
const bool mustFIFO = (resId.getType() == RESOURCE_MMAPV1_FLUSH);
// New lock request
if (conflicts(mode, lock->grantedModes)
|| (mustFIFO && conflicts(mode, lock->conflictModes))) {
request->status = LockRequest::STATUS_WAITING;
request->mode = mode;
request->convertMode = MODE_NONE;
// Put it on the conflict queue. This is the place where various policies could be
// applied for where in the wait queue does a request go.
lock->addToConflictQueue(request);
lock->changeConflictModeCount(mode, LockHead::Increment);
return LOCK_WAITING;
}
else { // No conflict, new request
request->status = LockRequest::STATUS_GRANTED;
request->mode = mode;
request->convertMode = MODE_NONE;
lock->addToGrantedQueue(request);
lock->changeGrantedModeCount(mode, LockHead::Increment);
return LOCK_OK;
}
}
else {
// If we are here, we already hold the lock in some mode. In order to keep it simple,
// we do not allow requesting a conversion while a lock is already waiting or pending
// conversion, hence the assertion below.
invariant(request->status == LockRequest::STATUS_GRANTED);
invariant(request->recursiveCount > 1);
invariant(request->mode != mode);
// Construct granted mask without our current mode, so that it is not counted as
// conflicting
uint32_t grantedModesWithoutCurrentRequest = 0;
// We start the counting at 1 below, because LockModesCount also includes MODE_NONE
// at position 0, which can never be acquired/granted.
for (uint32_t i = 1; i < LockModesCount; i++) {
const uint32_t currentRequestHolds =
(request->mode == static_cast<LockMode>(i) ? 1 : 0);
if (lock->grantedCounts[i] > currentRequestHolds) {
grantedModesWithoutCurrentRequest |= modeMask(static_cast<LockMode>(i));
}
}
// This check favours conversion requests over pending requests. For example:
//
// T1 requests lock L in IS
// T2 requests lock L in X
// T1 then upgrades L from IS -> S
//
// Because the check does not look into the conflict modes bitmap, it will grant L to
// T1 in S mode, instead of block, which would otherwise cause deadlock.
if (conflicts(mode, grantedModesWithoutCurrentRequest)) {
request->status = LockRequest::STATUS_CONVERTING;
request->convertMode = mode;
lock->conversionsCount++;
lock->changeGrantedModeCount(request->convertMode, LockHead::Increment);
return LOCK_WAITING;
}
else { // No conflict, existing request
lock->changeGrantedModeCount(mode, LockHead::Increment);
lock->changeGrantedModeCount(request->mode, LockHead::Decrement);
request->mode = mode;
return LOCK_OK;
}
}
}