mirror of https://github.com/facebook/rocksdb.git
94 lines
3.3 KiB
C++
94 lines
3.3 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under the BSD-style license found in the
|
|
// LICENSE file in the root directory of this source tree. An additional grant
|
|
// of patent rights can be found in the PATENTS file in the same directory.
|
|
// This source code is also licensed under the GPLv2 license found in the
|
|
// COPYING file in the root directory of this source tree.
|
|
//
|
|
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#pragma once
|
|
|
|
#include <atomic>
|
|
#include <functional>
|
|
#include <memory>
|
|
#include <unordered_map>
|
|
#include <vector>
|
|
|
|
#include "util/autovector.h"
|
|
#include "port/port.h"
|
|
|
|
namespace rocksdb {
|
|
|
|
// Cleanup function that will be called for a stored thread local
|
|
// pointer (if not NULL) when one of the following happens:
|
|
// (1) a thread terminates
|
|
// (2) a ThreadLocalPtr is destroyed
|
|
typedef void (*UnrefHandler)(void* ptr);
|
|
|
|
// ThreadLocalPtr stores only values of pointer type. Different from
|
|
// the usual thread-local-storage, ThreadLocalPtr has the ability to
|
|
// distinguish data coming from different threads and different
|
|
// ThreadLocalPtr instances. For example, if a regular thread_local
|
|
// variable A is declared in DBImpl, two DBImpl objects would share
|
|
// the same A. However, a ThreadLocalPtr that is defined under the
|
|
// scope of DBImpl can avoid such confliction. As a result, its memory
|
|
// usage would be O(# of threads * # of ThreadLocalPtr instances).
|
|
class ThreadLocalPtr {
|
|
public:
|
|
explicit ThreadLocalPtr(UnrefHandler handler = nullptr);
|
|
|
|
~ThreadLocalPtr();
|
|
|
|
// Return the current pointer stored in thread local
|
|
void* Get() const;
|
|
|
|
// Set a new pointer value to the thread local storage.
|
|
void Reset(void* ptr);
|
|
|
|
// Atomically swap the supplied ptr and return the previous value
|
|
void* Swap(void* ptr);
|
|
|
|
// Atomically compare the stored value with expected. Set the new
|
|
// pointer value to thread local only if the comparison is true.
|
|
// Otherwise, expected returns the stored value.
|
|
// Return true on success, false on failure
|
|
bool CompareAndSwap(void* ptr, void*& expected);
|
|
|
|
// Reset all thread local data to replacement, and return non-nullptr
|
|
// data for all existing threads
|
|
void Scrape(autovector<void*>* ptrs, void* const replacement);
|
|
|
|
typedef std::function<void(void*, void*)> FoldFunc;
|
|
// Update res by applying func on each thread-local value. Holds a lock that
|
|
// prevents unref handler from running during this call, but clients must
|
|
// still provide external synchronization since the owning thread can
|
|
// access the values without internal locking, e.g., via Get() and Reset().
|
|
void Fold(FoldFunc func, void* res);
|
|
|
|
// Add here for testing
|
|
// Return the next available Id without claiming it
|
|
static uint32_t TEST_PeekId();
|
|
|
|
// Initialize the static singletons of the ThreadLocalPtr.
|
|
//
|
|
// If this function is not called, then the singletons will be
|
|
// automatically initialized when they are used.
|
|
//
|
|
// Calling this function twice or after the singletons have been
|
|
// initialized will be no-op.
|
|
static void InitSingletons();
|
|
|
|
class StaticMeta;
|
|
|
|
private:
|
|
|
|
static StaticMeta* Instance();
|
|
|
|
const uint32_t id_;
|
|
};
|
|
|
|
} // namespace rocksdb
|