Revision 0d4a2b733070a1bd52f981313f9e17f126701407 authored by Yi Wu on 04 August 2017, 20:09:56 UTC, committed by Facebook Github Bot on 04 August 2017, 20:12:07 UTC
Summary: The FsyncFiles background job call Fsync() periodically for blob files. However it can access WritableFileWriter concurrently with a Put() or Write(). And WritableFileWriter does not support concurrent access. It will lead to WritableFileWriter buffer being flush with same content twice, and blob file end up corrupted. Fixing by simply let FsyncFiles hold write_mutex_. Closes https://github.com/facebook/rocksdb/pull/2685 Differential Revision: D5561908 Pulled By: yiwu-arbug fbshipit-source-id: f0bb5bcab0e05694e053b8c49eab43640721e872
1 parent 627c9f1
mutexlock.h
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root 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.
#pragma once
#include <assert.h>
#include <atomic>
#include <mutex>
#include <thread>
#include "port/port.h"
namespace rocksdb {
// Helper class that locks a mutex on construction and unlocks the mutex when
// the destructor of the MutexLock object is invoked.
//
// Typical usage:
//
// void MyClass::MyMethod() {
// MutexLock l(&mu_); // mu_ is an instance variable
// ... some complex code, possibly with multiple return paths ...
// }
class MutexLock {
public:
explicit MutexLock(port::Mutex *mu) : mu_(mu) {
this->mu_->Lock();
}
~MutexLock() { this->mu_->Unlock(); }
private:
port::Mutex *const mu_;
// No copying allowed
MutexLock(const MutexLock&);
void operator=(const MutexLock&);
};
//
// Acquire a ReadLock on the specified RWMutex.
// The Lock will be automatically released then the
// object goes out of scope.
//
class ReadLock {
public:
explicit ReadLock(port::RWMutex *mu) : mu_(mu) {
this->mu_->ReadLock();
}
~ReadLock() { this->mu_->ReadUnlock(); }
private:
port::RWMutex *const mu_;
// No copying allowed
ReadLock(const ReadLock&);
void operator=(const ReadLock&);
};
//
// Automatically unlock a locked mutex when the object is destroyed
//
class ReadUnlock {
public:
explicit ReadUnlock(port::RWMutex *mu) : mu_(mu) { mu->AssertHeld(); }
~ReadUnlock() { mu_->ReadUnlock(); }
private:
port::RWMutex *const mu_;
// No copying allowed
ReadUnlock(const ReadUnlock &) = delete;
ReadUnlock &operator=(const ReadUnlock &) = delete;
};
//
// Acquire a WriteLock on the specified RWMutex.
// The Lock will be automatically released then the
// object goes out of scope.
//
class WriteLock {
public:
explicit WriteLock(port::RWMutex *mu) : mu_(mu) {
this->mu_->WriteLock();
}
~WriteLock() { this->mu_->WriteUnlock(); }
private:
port::RWMutex *const mu_;
// No copying allowed
WriteLock(const WriteLock&);
void operator=(const WriteLock&);
};
//
// SpinMutex has very low overhead for low-contention cases. Method names
// are chosen so you can use std::unique_lock or std::lock_guard with it.
//
class SpinMutex {
public:
SpinMutex() : locked_(false) {}
bool try_lock() {
auto currently_locked = locked_.load(std::memory_order_relaxed);
return !currently_locked &&
locked_.compare_exchange_weak(currently_locked, true,
std::memory_order_acquire,
std::memory_order_relaxed);
}
void lock() {
for (size_t tries = 0;; ++tries) {
if (try_lock()) {
// success
break;
}
port::AsmVolatilePause();
if (tries > 100) {
std::this_thread::yield();
}
}
}
void unlock() { locked_.store(false, std::memory_order_release); }
private:
std::atomic<bool> locked_;
};
} // namespace rocksdb
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