storage/SQLiteMutex.h
author Chris H-C <chutten@mozilla.com>
Mon, 04 Jul 2016 11:16:05 -0400
changeset 312997 df28918fe2361f0b54ca9ce4773a29c4c0675d06
parent 288579 ec1879bdc5dc04d4a810c5177be94eb9b3218b9b
permissions -rw-r--r--
bug 1218576 - Support remote accumulation via JS histograms. r=gfritzsche The JS histograms, too, need to dispatch their accumulations from child to parent. JSHistograms_Add now only supports histograms that are in gHistogramsMap or that were created in the parent process. After bug 1288745, maybe we'll be able to change this to be less convoluted. MozReview-Commit-ID: 3qTH89YKbGP

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_storage_SQLiteMutex_h_
#define mozilla_storage_SQLiteMutex_h_

#include "mozilla/BlockingResourceBase.h"
#include "sqlite3.h"

namespace mozilla {
namespace storage {

/**
 * Wrapper class for sqlite3_mutexes.  To be used whenever we want to use a
 * sqlite3_mutex.
 *
 * @warning Never EVER wrap the same sqlite3_mutex with a different SQLiteMutex.
 *          If you do this, you void the deadlock detector's warranty!
 */
class SQLiteMutex : private BlockingResourceBase
{
public:
  /**
   * Constructs a wrapper for a sqlite3_mutex that has deadlock detecting.
   *
   * @param aName
   *        A name which can be used to reference this mutex.
   */
  explicit SQLiteMutex(const char *aName)
  : BlockingResourceBase(aName, eMutex)
  , mMutex(nullptr)
  {
  }

  /**
   * Sets the mutex that we are wrapping.  We generally do not have access to
   * our mutex at class construction, so we have to set it once we get access to
   * it.
   *
   * @param aMutex
   *        The sqlite3_mutex that we are going to wrap.
   */
  void initWithMutex(sqlite3_mutex *aMutex)
  {
    NS_ASSERTION(aMutex, "You must pass in a valid mutex!");
    NS_ASSERTION(!mMutex, "A mutex has already been set for this!");
    mMutex = aMutex;
  }

#if !defined(DEBUG) || defined(MOZ_SYSTEM_SQLITE)
  /**
   * Acquires the mutex.
   */
  void lock()
  {
    sqlite3_mutex_enter(mMutex);
  }

  /**
   * Releases the mutex.
   */
  void unlock()
  {
    sqlite3_mutex_leave(mMutex);
  }

  /**
   * Asserts that the current thread owns the mutex.
   */
  void assertCurrentThreadOwns()
  {
  }

  /**
   * Asserts that the current thread does not own the mutex.
   */
  void assertNotCurrentThreadOwns()
  {
  }

#else
  void lock()
  {
    NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");

    // While SQLite Mutexes may be recursive, in our own code we do not want to
    // treat them as such.

    CheckAcquire();
    sqlite3_mutex_enter(mMutex);
    Acquire(); // Call is protected by us holding the mutex.
  }

  void unlock()
  {
    NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");

    // While SQLite Mutexes may be recursive, in our own code we do not want to
    // treat them as such.
    Release(); // Call is protected by us holding the mutex.
    sqlite3_mutex_leave(mMutex);
  }

  void assertCurrentThreadOwns()
  {
    NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");
    NS_ASSERTION(sqlite3_mutex_held(mMutex),
                 "Mutex is not held, but we expect it to be!");
  }

  void assertNotCurrentThreadOwns()
  {
    NS_ASSERTION(mMutex, "No mutex associated with this wrapper!");
    NS_ASSERTION(sqlite3_mutex_notheld(mMutex),
                 "Mutex is held, but we expect it to not be!");
  }
#endif // ifndef DEBUG

private:
  sqlite3_mutex *mMutex;
};

/**
 * Automatically acquires the mutex when it enters scope, and releases it when
 * it leaves scope.
 */
class MOZ_STACK_CLASS SQLiteMutexAutoLock
{
public:
  explicit SQLiteMutexAutoLock(SQLiteMutex &aMutex)
  : mMutex(aMutex)
  {
    mMutex.lock();
  }

  ~SQLiteMutexAutoLock()
  {
    mMutex.unlock();
  }

private:
  SQLiteMutex &mMutex;
};

/**
 * Automatically releases the mutex when it enters scope, and acquires it when
 * it leaves scope.
 */
class MOZ_STACK_CLASS SQLiteMutexAutoUnlock
{
public:
  explicit SQLiteMutexAutoUnlock(SQLiteMutex &aMutex)
  : mMutex(aMutex)
  {
    mMutex.unlock();
  }

  ~SQLiteMutexAutoUnlock()
  {
    mMutex.lock();
  }

private:
  SQLiteMutex &mMutex;
};

} // namespace storage
} // namespace mozilla

#endif // mozilla_storage_SQLiteMutex_h_