rocksdb/monitoring/instrumented_mutex.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).

#pragma once

#include "monitoring/statistics.h"
#include "port/port.h"
#include "rocksdb/statistics.h"
#include "rocksdb/system_clock.h"
#include "rocksdb/thread_status.h"
#include "util/stop_watch.h"

namespace ROCKSDB_NAMESPACE {
class InstrumentedCondVar;

// A wrapper class for port::Mutex that provides additional layer
// for collecting stats and instrumentation.
class InstrumentedMutex {
 public:
  explicit InstrumentedMutex(bool adaptive = false)
      : mutex_(adaptive), stats_(nullptr), clock_(nullptr), stats_code_(0) {}

  explicit InstrumentedMutex(SystemClock* clock, bool adaptive = false)
      : mutex_(adaptive), stats_(nullptr), clock_(clock), stats_code_(0) {}

  InstrumentedMutex(Statistics* stats, SystemClock* clock, int stats_code,
                    bool adaptive = false)
      : mutex_(adaptive),
        stats_(stats),
        clock_(clock),
        stats_code_(stats_code) {}

#ifdef COERCE_CONTEXT_SWITCH
  InstrumentedMutex(Statistics* stats, SystemClock* clock, int stats_code,
                    InstrumentedCondVar* bg_cv, bool adaptive = false)
      : mutex_(adaptive),
        stats_(stats),
        clock_(clock),
        stats_code_(stats_code),
        bg_cv_(bg_cv) {}
#endif

  void Lock();

  void Unlock() { mutex_.Unlock(); }

  void AssertHeld() { mutex_.AssertHeld(); }

 private:
  void LockInternal();
  friend class InstrumentedCondVar;
  port::Mutex mutex_;
  Statistics* stats_;
  SystemClock* clock_;
  int stats_code_;
#ifdef COERCE_CONTEXT_SWITCH
  InstrumentedCondVar* bg_cv_ = nullptr;
#endif
};

class ALIGN_AS(CACHE_LINE_SIZE) CacheAlignedInstrumentedMutex
    : public InstrumentedMutex {
  using InstrumentedMutex::InstrumentedMutex;
};
static_assert(alignof(CacheAlignedInstrumentedMutex) != CACHE_LINE_SIZE ||
              sizeof(CacheAlignedInstrumentedMutex) % CACHE_LINE_SIZE == 0);

// RAII wrapper for InstrumentedMutex
class InstrumentedMutexLock {
 public:
  explicit InstrumentedMutexLock(InstrumentedMutex* mutex) : mutex_(mutex) {
    mutex_->Lock();
  }

  ~InstrumentedMutexLock() { mutex_->Unlock(); }

 private:
  InstrumentedMutex* const mutex_;
  InstrumentedMutexLock(const InstrumentedMutexLock&) = delete;
  void operator=(const InstrumentedMutexLock&) = delete;
};

// RAII wrapper for temporary releasing InstrumentedMutex inside
// InstrumentedMutexLock
class InstrumentedMutexUnlock {
 public:
  explicit InstrumentedMutexUnlock(InstrumentedMutex* mutex) : mutex_(mutex) {
    mutex_->Unlock();
  }

  ~InstrumentedMutexUnlock() { mutex_->Lock(); }

 private:
  InstrumentedMutex* const mutex_;
  InstrumentedMutexUnlock(const InstrumentedMutexUnlock&) = delete;
  void operator=(const InstrumentedMutexUnlock&) = delete;
};

class InstrumentedCondVar {
 public:
  explicit InstrumentedCondVar(InstrumentedMutex* instrumented_mutex)
      : cond_(&(instrumented_mutex->mutex_)),
        stats_(instrumented_mutex->stats_),
        clock_(instrumented_mutex->clock_),
        stats_code_(instrumented_mutex->stats_code_) {}

  void Wait();

  bool TimedWait(uint64_t abs_time_us);

  void Signal() { cond_.Signal(); }

  void SignalAll() { cond_.SignalAll(); }

 private:
  void WaitInternal();
  bool TimedWaitInternal(uint64_t abs_time_us);
  port::CondVar cond_;
  Statistics* stats_;
  SystemClock* clock_;
  int stats_code_;
};

}  // namespace ROCKSDB_NAMESPACE