Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 180 insertions, 0 deletions

diff --git a/src/rocksdb/util/mutexlock.h b/src/rocksdb/util/mutexlock.h
new file mode 100644
index 000000000..94066b29e
--- /dev/null
+++ b/src/rocksdb/util/mutexlock.h
@@ -0,0 +1,180 @@
+//  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_NAMESPACE {
+
+// 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(); }
+  // No copying allowed
+  MutexLock(const MutexLock &) = delete;
+  void operator=(const MutexLock &) = delete;
+
+  ~MutexLock() { this->mu_->Unlock(); }
+
+ private:
+  port::Mutex *const mu_;
+};
+
+//
+// Acquire a ReadLock on the specified RWMutex.
+// The Lock will be automatically released when the
+// object goes out of scope.
+//
+class ReadLock {
+ public:
+  explicit ReadLock(port::RWMutex *mu) : mu_(mu) { this->mu_->ReadLock(); }
+  // No copying allowed
+  ReadLock(const ReadLock &) = delete;
+  void operator=(const ReadLock &) = delete;
+
+  ~ReadLock() { this->mu_->ReadUnlock(); }
+
+ private:
+  port::RWMutex *const mu_;
+};
+
+//
+// Automatically unlock a locked mutex when the object is destroyed
+//
+class ReadUnlock {
+ public:
+  explicit ReadUnlock(port::RWMutex *mu) : mu_(mu) { mu->AssertHeld(); }
+  // No copying allowed
+  ReadUnlock(const ReadUnlock &) = delete;
+  ReadUnlock &operator=(const ReadUnlock &) = delete;
+
+  ~ReadUnlock() { mu_->ReadUnlock(); }
+
+ private:
+  port::RWMutex *const mu_;
+};
+
+//
+// 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(); }
+  // No copying allowed
+  WriteLock(const WriteLock &) = delete;
+  void operator=(const WriteLock &) = delete;
+
+  ~WriteLock() { this->mu_->WriteUnlock(); }
+
+ private:
+  port::RWMutex *const mu_;
+};
+
+//
+// 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_;
+};
+
+// We want to prevent false sharing
+template <class T>
+struct ALIGN_AS(CACHE_LINE_SIZE) LockData {
+  T lock_;
+};
+
+//
+// Inspired by Guava: https://github.com/google/guava/wiki/StripedExplained
+// A striped Lock. This offers the underlying lock striping similar
+// to that of ConcurrentHashMap in a reusable form, and extends it for
+// semaphores and read-write locks. Conceptually, lock striping is the technique
+// of dividing a lock into many <i>stripes</i>, increasing the granularity of a
+// single lock and allowing independent operations to lock different stripes and
+// proceed concurrently, instead of creating contention for a single lock.
+//
+template <class T, class P>
+class Striped {
+ public:
+  Striped(size_t stripes, std::function<uint64_t(const P &)> hash)
+      : stripes_(stripes), hash_(hash) {
+    locks_ = reinterpret_cast<LockData<T> *>(
+        port::cacheline_aligned_alloc(sizeof(LockData<T>) * stripes));
+    for (size_t i = 0; i < stripes; i++) {
+      new (&locks_[i]) LockData<T>();
+    }
+  }
+
+  virtual ~Striped() {
+    if (locks_ != nullptr) {
+      assert(stripes_ > 0);
+      for (size_t i = 0; i < stripes_; i++) {
+        locks_[i].~LockData<T>();
+      }
+      port::cacheline_aligned_free(locks_);
+    }
+  }
+
+  T *get(const P &key) {
+    uint64_t h = hash_(key);
+    size_t index = h % stripes_;
+    return &reinterpret_cast<LockData<T> *>(&locks_[index])->lock_;
+  }
+
+ private:
+  size_t stripes_;
+  LockData<T> *locks_;
+  std::function<uint64_t(const P &)> hash_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE