/*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* objects of a parent. accessAllThreads() initializes an accessor which holds
* a global lock *that blocks all creation and destruction of ThreadLocal
* objects with the same Tag* and can be used as an iterable container.
+ * accessAllThreads() can race with destruction of thread-local elements. We
+ * provide a strict mode which is dangerous because it requires the access lock
+ * to be held while destroying thread-local elements which could cause
+ * deadlocks. We gate this mode behind the AccessModeStrict template parameter.
*
* Intended use is for frequent write, infrequent read data access patterns such
* as counters.
#include <folly/Portability.h>
#include <folly/ScopeGuard.h>
#include <folly/SharedMutex.h>
+#include <folly/detail/ThreadLocalDetail.h>
#include <type_traits>
#include <utility>
namespace folly {
-enum class TLPDestructionMode {
- THIS_THREAD,
- ALL_THREADS
-};
-} // namespace
-#include <folly/detail/ThreadLocalDetail.h>
+template <class T, class Tag, class AccessMode>
+class ThreadLocalPtr;
-namespace folly {
-
-template<class T, class Tag> class ThreadLocalPtr;
-
-template<class T, class Tag=void>
+template <class T, class Tag = void, class AccessMode = void>
class ThreadLocal {
public:
constexpr ThreadLocal() : constructor_([]() {
tlp_.reset(newPtr);
}
- typedef typename ThreadLocalPtr<T,Tag>::Accessor Accessor;
+ typedef typename ThreadLocalPtr<T, Tag, AccessMode>::Accessor Accessor;
Accessor accessAllThreads() const {
return tlp_.accessAllThreads();
}
return ptr;
}
- mutable ThreadLocalPtr<T,Tag> tlp_;
+ mutable ThreadLocalPtr<T, Tag, AccessMode> tlp_;
std::function<T*()> constructor_;
};
* with __declspec(thread)
*/
-template<class T, class Tag=void>
+template <class T, class Tag = void, class AccessMode = void>
class ThreadLocalPtr {
private:
- typedef threadlocal_detail::StaticMeta<Tag> StaticMeta;
+ typedef threadlocal_detail::StaticMeta<Tag, AccessMode> StaticMeta;
+
public:
constexpr ThreadLocalPtr() : id_() {}
// Can be used as an iterable container.
// Use accessAllThreads() to obtain one.
class Accessor {
- friend class ThreadLocalPtr<T,Tag>;
+ friend class ThreadLocalPtr<T, Tag, AccessMode>;
threadlocal_detail::StaticMetaBase& meta_;
SharedMutex* accessAllThreadsLock_;
}
Accessor()
- : meta_(threadlocal_detail::StaticMeta<Tag>::instance()),
+ : meta_(threadlocal_detail::StaticMeta<Tag, AccessMode>::instance()),
accessAllThreadsLock_(nullptr),
lock_(nullptr),
id_(0) {}
private:
explicit Accessor(uint32_t id)
- : meta_(threadlocal_detail::StaticMeta<Tag>::instance()),
+ : meta_(threadlocal_detail::StaticMeta<Tag, AccessMode>::instance()),
accessAllThreadsLock_(&meta_.accessAllThreadsLock_),
lock_(&meta_.lock_) {
accessAllThreadsLock_->lock();
mutable typename StaticMeta::EntryID id_;
};
-} // namespace folly
+} // namespace folly