rocksdb/util/thread_local.cc
sdong 4c49fedaf1 Use ustricter consistency in thread local operations
Summary:
ThreadSanitizer complains data race of super version and version's destructor with Get(). This patch will fix those warning.

The warning is likely from ColumnFamilyData::ReturnThreadLocalSuperVersion(). With relaxed consistency of CAS, reading the data of the super version can technically happen after swapping it in, enabling the background thread to clean it up.

Test Plan: make all check

Reviewers: rven, igor, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D32265
2015-01-27 13:56:03 -08:00

243 lines
6.7 KiB
C++

// Copyright (c) 2013, 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.
//
// 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.
#include "util/thread_local.h"
#include "util/mutexlock.h"
#include "port/likely.h"
#include <stdlib.h>
namespace rocksdb {
port::Mutex ThreadLocalPtr::StaticMeta::mutex_;
#if !defined(OS_MACOSX)
__thread ThreadLocalPtr::ThreadData* ThreadLocalPtr::StaticMeta::tls_ = nullptr;
#endif
ThreadLocalPtr::StaticMeta* ThreadLocalPtr::Instance() {
static ThreadLocalPtr::StaticMeta inst;
return &inst;
}
void ThreadLocalPtr::StaticMeta::OnThreadExit(void* ptr) {
auto* tls = static_cast<ThreadData*>(ptr);
assert(tls != nullptr);
auto* inst = Instance();
pthread_setspecific(inst->pthread_key_, nullptr);
MutexLock l(&mutex_);
inst->RemoveThreadData(tls);
// Unref stored pointers of current thread from all instances
uint32_t id = 0;
for (auto& e : tls->entries) {
void* raw = e.ptr.load();
if (raw != nullptr) {
auto unref = inst->GetHandler(id);
if (unref != nullptr) {
unref(raw);
}
}
++id;
}
// Delete thread local structure no matter if it is Mac platform
delete tls;
}
ThreadLocalPtr::StaticMeta::StaticMeta() : next_instance_id_(0) {
if (pthread_key_create(&pthread_key_, &OnThreadExit) != 0) {
abort();
}
head_.next = &head_;
head_.prev = &head_;
}
void ThreadLocalPtr::StaticMeta::AddThreadData(ThreadLocalPtr::ThreadData* d) {
mutex_.AssertHeld();
d->next = &head_;
d->prev = head_.prev;
head_.prev->next = d;
head_.prev = d;
}
void ThreadLocalPtr::StaticMeta::RemoveThreadData(
ThreadLocalPtr::ThreadData* d) {
mutex_.AssertHeld();
d->next->prev = d->prev;
d->prev->next = d->next;
d->next = d->prev = d;
}
ThreadLocalPtr::ThreadData* ThreadLocalPtr::StaticMeta::GetThreadLocal() {
#if defined(OS_MACOSX)
// Make this local variable name look like a member variable so that we
// can share all the code below
ThreadData* tls_ =
static_cast<ThreadData*>(pthread_getspecific(Instance()->pthread_key_));
#endif
if (UNLIKELY(tls_ == nullptr)) {
auto* inst = Instance();
tls_ = new ThreadData();
{
// Register it in the global chain, needs to be done before thread exit
// handler registration
MutexLock l(&mutex_);
inst->AddThreadData(tls_);
}
// Even it is not OS_MACOSX, need to register value for pthread_key_ so that
// its exit handler will be triggered.
if (pthread_setspecific(inst->pthread_key_, tls_) != 0) {
{
MutexLock l(&mutex_);
inst->RemoveThreadData(tls_);
}
delete tls_;
abort();
}
}
return tls_;
}
void* ThreadLocalPtr::StaticMeta::Get(uint32_t id) const {
auto* tls = GetThreadLocal();
if (UNLIKELY(id >= tls->entries.size())) {
return nullptr;
}
return tls->entries[id].ptr.load(std::memory_order_acquire);
}
void ThreadLocalPtr::StaticMeta::Reset(uint32_t id, void* ptr) {
auto* tls = GetThreadLocal();
if (UNLIKELY(id >= tls->entries.size())) {
// Need mutex to protect entries access within ReclaimId
MutexLock l(&mutex_);
tls->entries.resize(id + 1);
}
tls->entries[id].ptr.store(ptr, std::memory_order_release);
}
void* ThreadLocalPtr::StaticMeta::Swap(uint32_t id, void* ptr) {
auto* tls = GetThreadLocal();
if (UNLIKELY(id >= tls->entries.size())) {
// Need mutex to protect entries access within ReclaimId
MutexLock l(&mutex_);
tls->entries.resize(id + 1);
}
return tls->entries[id].ptr.exchange(ptr, std::memory_order_acquire);
}
bool ThreadLocalPtr::StaticMeta::CompareAndSwap(uint32_t id, void* ptr,
void*& expected) {
auto* tls = GetThreadLocal();
if (UNLIKELY(id >= tls->entries.size())) {
// Need mutex to protect entries access within ReclaimId
MutexLock l(&mutex_);
tls->entries.resize(id + 1);
}
return tls->entries[id].ptr.compare_exchange_strong(
expected, ptr, std::memory_order_release, std::memory_order_relaxed);
}
void ThreadLocalPtr::StaticMeta::Scrape(uint32_t id, autovector<void*>* ptrs,
void* const replacement) {
MutexLock l(&mutex_);
for (ThreadData* t = head_.next; t != &head_; t = t->next) {
if (id < t->entries.size()) {
void* ptr =
t->entries[id].ptr.exchange(replacement, std::memory_order_acquire);
if (ptr != nullptr) {
ptrs->push_back(ptr);
}
}
}
}
void ThreadLocalPtr::StaticMeta::SetHandler(uint32_t id, UnrefHandler handler) {
MutexLock l(&mutex_);
handler_map_[id] = handler;
}
UnrefHandler ThreadLocalPtr::StaticMeta::GetHandler(uint32_t id) {
mutex_.AssertHeld();
auto iter = handler_map_.find(id);
if (iter == handler_map_.end()) {
return nullptr;
}
return iter->second;
}
uint32_t ThreadLocalPtr::StaticMeta::GetId() {
MutexLock l(&mutex_);
if (free_instance_ids_.empty()) {
return next_instance_id_++;
}
uint32_t id = free_instance_ids_.back();
free_instance_ids_.pop_back();
return id;
}
uint32_t ThreadLocalPtr::StaticMeta::PeekId() const {
MutexLock l(&mutex_);
if (!free_instance_ids_.empty()) {
return free_instance_ids_.back();
}
return next_instance_id_;
}
void ThreadLocalPtr::StaticMeta::ReclaimId(uint32_t id) {
// This id is not used, go through all thread local data and release
// corresponding value
MutexLock l(&mutex_);
auto unref = GetHandler(id);
for (ThreadData* t = head_.next; t != &head_; t = t->next) {
if (id < t->entries.size()) {
void* ptr = t->entries[id].ptr.exchange(nullptr);
if (ptr != nullptr && unref != nullptr) {
unref(ptr);
}
}
}
handler_map_[id] = nullptr;
free_instance_ids_.push_back(id);
}
ThreadLocalPtr::ThreadLocalPtr(UnrefHandler handler)
: id_(Instance()->GetId()) {
if (handler != nullptr) {
Instance()->SetHandler(id_, handler);
}
}
ThreadLocalPtr::~ThreadLocalPtr() {
Instance()->ReclaimId(id_);
}
void* ThreadLocalPtr::Get() const {
return Instance()->Get(id_);
}
void ThreadLocalPtr::Reset(void* ptr) {
Instance()->Reset(id_, ptr);
}
void* ThreadLocalPtr::Swap(void* ptr) {
return Instance()->Swap(id_, ptr);
}
bool ThreadLocalPtr::CompareAndSwap(void* ptr, void*& expected) {
return Instance()->CompareAndSwap(id_, ptr, expected);
}
void ThreadLocalPtr::Scrape(autovector<void*>* ptrs, void* const replacement) {
Instance()->Scrape(id_, ptrs, replacement);
}
} // namespace rocksdb