void StaticMetaBase::reserve(EntryID* id) {
auto& meta = *this;
ThreadEntry* threadEntry = (*threadEntry_)();
size_t prevCapacity = threadEntry->getElementsCapacity();
uint32_t idval = id->getOrAllocate(meta);
if (prevCapacity > idval) {
return;
}
size_t newCapacity;
ElementWrapper* reallocated = reallocate(threadEntry, idval, newCapacity);
// Success, update the entry
{
std::lock_guard<std::mutex> g(meta.lock_);
if (prevCapacity == 0) {
meta.push_back(threadEntry);
}
if (reallocated) {
/*
* Note: we need to hold the meta lock when copying data out of
* the old vector, because some other thread might be
* destructing a ThreadLocal and writing to the elements vector
* of this thread.
*/
if (prevCapacity != 0) {
memcpy(
reallocated,
threadEntry->elements,
sizeof(*reallocated) * prevCapacity);
}
std::swap(reallocated, threadEntry->elements);
}
for (size_t i = prevCapacity; i < newCapacity; i++) {
threadEntry->elements[i].node.initZero(threadEntry, i);
}
threadEntry->setElementsCapacity(newCapacity);
}
free(reallocated);
}
void StaticMetaBase::destroy(EntryID* ent) {
try {
auto& meta = *this;
// Elements in other threads that use this id.
std::vector<ElementWrapper> elements;
{
SharedMutex::WriteHolder wlock(nullptr);
if (meta.strict_) {
/*
* In strict mode, the logic guarantees per-thread instances are
* destroyed by the moment ThreadLocal<> dtor returns.
* In order to achieve that, we should wait until concurrent
* onThreadExit() calls (that might acquire ownership over per-thread
* instances in order to destroy them) are finished.
*/
wlock = SharedMutex::WriteHolder(meta.accessAllThreadsLock_);
}
{
std::lock_guard<std::mutex> g(meta.lock_);
uint32_t id = ent->value.exchange(kEntryIDInvalid);
if (id == kEntryIDInvalid) {
return;
}
auto& node = meta.head_.elements[id].node;
while (!node.empty()) {
auto* next = node.getNext();
next->eraseZero();
ThreadEntry* e = next->parent;
auto elementsCapacity = e->getElementsCapacity();
if (id < elementsCapacity && e->elements[id].ptr) {
elements.push_back(e->elements[id]);
/*
* Writing another thread's ThreadEntry from here is fine;
* the only other potential reader is the owning thread --
* from onThreadExit (which grabs the lock, so is properly
* synchronized with us) or from get(), which also grabs
* the lock if it needs to resize the elements vector.
*
* We can't conflict with reads for a get(id), because
* it's illegal to call get on a thread local that's
* destructing.
*/
e->elements[id].ptr = nullptr;
e->elements[id].deleter1 = nullptr;
e->elements[id].ownsDeleter = false;
}
}
meta.freeIds_.push_back(id);
}
}
// Delete elements outside the locks.
for (ElementWrapper& elem : elements) {
if (elem.dispose(TLPDestructionMode::ALL_THREADS)) {
elem.cleanup();
}
}
} catch (...) { // Just in case we get a lock error or something anyway...
LOG(WARNING) << "Destructor discarding an exception that was thrown.";
}
}
uint32_t StaticMetaBase::elementsCapacity() const {
ThreadEntry* threadEntry = (*threadEntry_)();
return FOLLY_LIKELY(!!threadEntry) ? threadEntry->getElementsCapacity() : 0;
}