mfbt/ChaosMode.h
author Petru Lingurar <petru.lingurar@softvision.ro>
Fri, 21 Dec 2018 08:56:47 +0000
changeset 501492 65621d0fe1262af0643cec37c23b2d9ec42588ad
parent 495750 1dd7a055bae0985e895946fa62b561feb8fbe78d
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1513938 - Enforce a Bundle size limit and drop `privateSession` if exceeds it. r=JanH, a=jcristau The `privateSession` key would normally allow persisting the Private Browsing session across OOMs in Activity's Bundle. We need to do that to avoid storing private, sensible data on disk like we do with the normal browsing session. In some cases `privateSession` would contain a lot of data which, along with other possible concurrent transactions could overflow Binder's buffer which has a limited fixed size, currently 1Mb. To avoid this, we will drop `privateSession` from the Bundle if the resulting size is greater than a _speculative_ size of 300KBs which would mean that in the case of an OOM all Private Browsing state would be lost. Bug 1515592 is filed to investigate for a better solution. Differential Revision: https://phabricator.services.mozilla.com/D15067

/* -*- 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 */