mfbt/ChaosMode.h
author Andrea Marchesini <amarchesini@mozilla.com>
Wed, 31 Oct 2018 18:30:18 +0100
changeset 500246 544498045a9cfe55968fa6500bffbc3181869fce
parent 493038 1dd7a055bae0985e895946fa62b561feb8fbe78d
child 505383 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1486698 - Update Fetch+Stream implementation to throw when the stream is disturbed or locked, r=bz In this patch, I went through any place in DOM fetch code, where there are ReadableStreams and update the locked, disturbed, readable checks. Because we expose streams more often, we need an extra care in the use of ErrorResult objects. JS streams can now throw exceptions and we need to handle them. This patch also fixes a bug in FileStreamReader::CloseAndRelease() which could be called in case mReader creation fails.

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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_ChaosMode_h
#define mozilla_ChaosMode_h

#include "mozilla/Atomics.h"
#include "mozilla/EnumSet.h"

#include <stdint.h>
#include <stdlib.h>

namespace mozilla {

enum ChaosFeature {
  None = 0x0,
  // Altering thread scheduling.
  ThreadScheduling = 0x1,
  // Altering network request scheduling.
  NetworkScheduling = 0x2,
  // Altering timer scheduling.
  TimerScheduling = 0x4,
  // Read and write less-than-requested amounts.
  IOAmounts = 0x8,
  // Iterate over hash tables in random order.
  HashTableIteration = 0x10,
  // Randomly refuse to use cached version of image (when allowed by spec).
  ImageCache = 0x20,
  // Delay dispatching threads to encourage dispatched tasks to run.
  TaskDispatching = 0x40,
  // Delay task running to encourage sending threads to run.
  TaskRunning = 0x80,
  Any = 0xffffffff,
};

namespace detail {
extern MFBT_DATA Atomic<uint32_t,
                        SequentiallyConsistent,
                        recordreplay::Behavior::DontPreserve> gChaosModeCounter;
extern MFBT_DATA ChaosFeature gChaosFeatures;
} // namespace detail

/**
 * When "chaos mode" is activated, code that makes implicitly nondeterministic
 * choices is encouraged to make random and extreme choices, to test more
 * code paths and uncover bugs.
 */
class ChaosMode
{
public:
  static void SetChaosFeature(ChaosFeature aChaosFeature)
  {
    detail::gChaosFeatures = aChaosFeature;
  }

  static bool isActive(ChaosFeature aFeature)
  {
    if (detail::gChaosModeCounter > 0) {
      return true;
    }
    return detail::gChaosFeatures & aFeature;
  }

  /**
   * Increase the chaos mode activation level. An equivalent number of
   * calls to leaveChaosMode must be made in order to restore the original
   * chaos mode state. If the activation level is nonzero all chaos mode
   * features are activated.
   */
  static void enterChaosMode()
  {
    detail::gChaosModeCounter++;
  }

  /**
   * Decrease the chaos mode activation level. See enterChaosMode().
   */
  static void leaveChaosMode()
  {
    MOZ_ASSERT(detail::gChaosModeCounter > 0);
    detail::gChaosModeCounter--;
  }

  /**
   * Returns a somewhat (but not uniformly) random uint32_t < aBound.
   * Not to be used for anything except ChaosMode, since it's not very random.
   */
  static uint32_t randomUint32LessThan(uint32_t aBound)
  {
    MOZ_ASSERT(aBound != 0);
    return uint32_t(rand()) % aBound;
  }
};

} /* namespace mozilla */

#endif /* mozilla_ChaosMode_h */