xpcom/threads/nsMemoryPressure.cpp
author Tim Huang <tihuang@mozilla.com>
Tue, 12 Dec 2017 15:25:49 -0600
changeset 398586 9c586454144b4eef9e9a8ab53e3d1a8c3f84ac3c
parent 366127 312f7a5a2c08d394a2403c837e5ee546dd4103d7
child 417625 6e79931930ee4bf830f79efc2322093b6e6190be
permissions -rw-r--r--
Bug 1404608 - Reveal the real operating system when fingerprinting resistance is enabled. r=arthuredelstein,smaug This patch makes Firefox not to lie about the real operating system when pref 'privacy.resistFingerprinting' is true. This will also change the testcase as well. MozReview-Commit-ID: Gdnp2lMU3wr

/* -*- 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/. */

#include "nsMemoryPressure.h"
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"

#include "nsThreadUtils.h"

using namespace mozilla;

static Atomic<int32_t, Relaxed> sMemoryPressurePending;
static_assert(MemPressure_None == 0,
              "Bad static initialization with the default constructor.");

MemoryPressureState
NS_GetPendingMemoryPressure()
{
  int32_t value = sMemoryPressurePending.exchange(MemPressure_None);
  return MemoryPressureState(value);
}

void
NS_DispatchEventualMemoryPressure(MemoryPressureState aState)
{
  /*
   * A new memory pressure event erases an ongoing memory pressure, but an
   * existing "new" memory pressure event takes precedence over a new "ongoing"
   * memory pressure event.
   */
  switch (aState) {
    case MemPressure_None:
      sMemoryPressurePending = MemPressure_None;
      break;
    case MemPressure_New:
      sMemoryPressurePending = MemPressure_New;
      break;
    case MemPressure_Ongoing:
      sMemoryPressurePending.compareExchange(MemPressure_None,
                                             MemPressure_Ongoing);
      break;
  }
}

nsresult
NS_DispatchMemoryPressure(MemoryPressureState aState)
{
  NS_DispatchEventualMemoryPressure(aState);
  nsCOMPtr<nsIRunnable> event = new Runnable("NS_DispatchEventualMemoryPressure");
  return NS_DispatchToMainThread(event);
}