gecko-dev/hal/gonk/GonkHal.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=8 et ft=cpp : */
/* Copyright 2012 Mozilla Foundation and Mozilla contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <errno.h>
#include <fcntl.h>
#include <linux/android_alarm.h>
#include <math.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <sys/resource.h>
#include <time.h>

#include "android/log.h"
#include "cutils/properties.h"
#include "hardware/hardware.h"
#include "hardware/lights.h"
#include "hardware_legacy/uevent.h"
#include "hardware_legacy/vibrator.h"
#include "hardware_legacy/power.h"

#include "base/message_loop.h"

#include "Hal.h"
#include "HalImpl.h"
#include "mozilla/dom/battery/Constants.h"
#include "mozilla/FileUtils.h"
#include "mozilla/Monitor.h"
#include "mozilla/Services.h"
#include "mozilla/Preferences.h"
#include "nsAlgorithm.h"
#include "nsPrintfCString.h"
#include "nsIObserver.h"
#include "nsIObserverService.h"
#include "nsIRunnable.h"
#include "nsScreenManagerGonk.h"
#include "nsThreadUtils.h"
#include "nsThreadUtils.h"
#include "nsIThread.h"
#include "nsXULAppAPI.h"
#include "OrientationObserver.h"
#include "UeventPoller.h"

#define LOG(args...)  __android_log_print(ANDROID_LOG_INFO, "Gonk", args)
#define NsecPerMsec  1000000
#define NsecPerSec   1000000000


using namespace mozilla;
using namespace mozilla::hal;

namespace mozilla {
namespace hal_impl {

namespace {

/**
 * This runnable runs for the lifetime of the program, once started.  It's
 * responsible for "playing" vibration patterns.
 */
class VibratorRunnable
  : public nsIRunnable
  , public nsIObserver
{
public:
  VibratorRunnable()
    : mMonitor("VibratorRunnable")
    , mIndex(0)
    , mShuttingDown(false)
  {
    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
    if (!os) {
      NS_WARNING("Could not get observer service!");
      return;
    }

    os->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, /* weak ref */ true);
  } 
  NS_DECL_ISUPPORTS
  NS_DECL_NSIRUNNABLE
  NS_DECL_NSIOBSERVER

  // Run on the main thread, not the vibrator thread.
  void Vibrate(const nsTArray<uint32_t> &pattern);
  void CancelVibrate();

private:
  Monitor mMonitor;

  // The currently-playing pattern.
  nsTArray<uint32_t> mPattern;

  // The index we're at in the currently-playing pattern.  If mIndex >=
  // mPattern.Length(), then we're not currently playing anything.
  uint32_t mIndex;

  // Set to true in our shutdown observer.  When this is true, we kill the
  // vibrator thread.
  bool mShuttingDown;
};

NS_IMPL_ISUPPORTS2(VibratorRunnable, nsIRunnable, nsIObserver);

NS_IMETHODIMP
VibratorRunnable::Run()
{
  MonitorAutoLock lock(mMonitor);

  // We currently assume that mMonitor.Wait(X) waits for X milliseconds.  But in
  // reality, the kernel might not switch to this thread for some time after the
  // wait expires.  So there's potential for some inaccuracy here.
  //
  // This doesn't worry me too much.  Note that we don't even start vibrating
  // immediately when VibratorRunnable::Vibrate is called -- we go through a
  // condvar onto another thread.  Better just to be chill about small errors in
  // the timing here.

  while (!mShuttingDown) {
    if (mIndex < mPattern.Length()) {
      uint32_t duration = mPattern[mIndex];
      if (mIndex % 2 == 0) {
        vibrator_on(duration);
      }
      mIndex++;
      mMonitor.Wait(PR_MillisecondsToInterval(duration));
    }
    else {
      mMonitor.Wait();
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
VibratorRunnable::Observe(nsISupports *subject, const char *topic,
                          const PRUnichar *data)
{
  MOZ_ASSERT(strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0);
  MonitorAutoLock lock(mMonitor);
  mShuttingDown = true;
  mMonitor.Notify();
  return NS_OK;
}

void
VibratorRunnable::Vibrate(const nsTArray<uint32_t> &pattern)
{
  MonitorAutoLock lock(mMonitor);
  mPattern = pattern;
  mIndex = 0;
  mMonitor.Notify();
}

void
VibratorRunnable::CancelVibrate()
{
  MonitorAutoLock lock(mMonitor);
  mPattern.Clear();
  mPattern.AppendElement(0);
  mIndex = 0;
  mMonitor.Notify();
}

VibratorRunnable *sVibratorRunnable = NULL;

void
EnsureVibratorThreadInitialized()
{
  if (sVibratorRunnable) {
    return;
  }

  nsRefPtr<VibratorRunnable> runnable = new VibratorRunnable();
  sVibratorRunnable = runnable;
  nsCOMPtr<nsIThread> thread;
  NS_NewThread(getter_AddRefs(thread), sVibratorRunnable);
}

} // anonymous namespace

void
Vibrate(const nsTArray<uint32_t> &pattern, const hal::WindowIdentifier &)
{
  EnsureVibratorThreadInitialized();
  sVibratorRunnable->Vibrate(pattern);
}

void
CancelVibrate(const hal::WindowIdentifier &)
{
  EnsureVibratorThreadInitialized();
  sVibratorRunnable->CancelVibrate();
}

namespace {

class BatteryUpdater : public nsRunnable {
public:
  NS_IMETHOD Run()
  {
    hal::BatteryInformation info;
    hal_impl::GetCurrentBatteryInformation(&info);
    hal::NotifyBatteryChange(info);
    return NS_OK;
  }
};

} // anonymous namespace

class BatteryObserver : public IUeventObserver,
                        public RefCounted<BatteryObserver>
{
public:
  BatteryObserver()
    :mUpdater(new BatteryUpdater())
  {
  }

  virtual void Notify(const NetlinkEvent &aEvent)
  {
    // this will run on IO thread
    NetlinkEvent *event = const_cast<NetlinkEvent*>(&aEvent);
    const char *subsystem = event->getSubsystem();
    // e.g. DEVPATH=/devices/platform/sec-battery/power_supply/battery
    const char *devpath = event->findParam("DEVPATH");
    if (strcmp(subsystem, "power_supply") == 0 &&
        strstr(devpath, "battery")) {
      // aEvent will be valid only in this method.
      NS_DispatchToMainThread(mUpdater);
    }
  }

private:
  nsRefPtr<BatteryUpdater> mUpdater;
};

// sBatteryObserver is owned by the IO thread. Only the IO thread may
// create or destroy it.
static BatteryObserver *sBatteryObserver = NULL;

static void
RegisterBatteryObserverIOThread()
{
  MOZ_ASSERT(MessageLoop::current() == XRE_GetIOMessageLoop());
  MOZ_ASSERT(!sBatteryObserver);

  sBatteryObserver = new BatteryObserver();
  RegisterUeventListener(sBatteryObserver);
}

void
EnableBatteryNotifications()
{
  XRE_GetIOMessageLoop()->PostTask(
      FROM_HERE,
      NewRunnableFunction(RegisterBatteryObserverIOThread));
}

static void
UnregisterBatteryObserverIOThread()
{
  MOZ_ASSERT(MessageLoop::current() == XRE_GetIOMessageLoop());
  MOZ_ASSERT(sBatteryObserver);

  UnregisterUeventListener(sBatteryObserver);
  delete sBatteryObserver;
  sBatteryObserver = NULL;
}

void
DisableBatteryNotifications()
{
  XRE_GetIOMessageLoop()->PostTask(
      FROM_HERE,
      NewRunnableFunction(UnregisterBatteryObserverIOThread));
}

void
GetCurrentBatteryInformation(hal::BatteryInformation *aBatteryInfo)
{
  static const int BATTERY_NOT_CHARGING = 0;
  static const int BATTERY_CHARGING_USB = 1;
  static const int BATTERY_CHARGING_AC  = 2;

  FILE *capacityFile = fopen("/sys/class/power_supply/battery/capacity", "r");
  double capacity = dom::battery::kDefaultLevel * 100;
  if (capacityFile) {
    fscanf(capacityFile, "%lf", &capacity);
    fclose(capacityFile);
  }

  FILE *chargingFile = fopen("/sys/class/power_supply/battery/charging_source", "r");
  int chargingSrc = BATTERY_CHARGING_USB;
  bool done = false;
  if (chargingFile) {
    fscanf(chargingFile, "%d", &chargingSrc);
    fclose(chargingFile);
    done = true;
  }

  if (!done) {
    // toro devices support
    chargingFile = fopen("/sys/class/power_supply/battery/status", "r");
    if (chargingFile) {
      char status[16];
      fscanf(chargingFile, "%s", &status);
      if (!strcmp(status, "Charging") || !strcmp(status, "Full")) {
        // no way here to know if we're charging from USB or AC.
        chargingSrc = BATTERY_CHARGING_USB;
      } else {
        chargingSrc = BATTERY_NOT_CHARGING;
      }
      fclose(chargingFile);
      done = true;
    }
  }

  #ifdef DEBUG
  if (chargingSrc != BATTERY_NOT_CHARGING &&
      chargingSrc != BATTERY_CHARGING_USB &&
      chargingSrc != BATTERY_CHARGING_AC) {
    HAL_LOG(("charging_source contained unknown value: %d", chargingSrc));
  }
  #endif

  aBatteryInfo->level() = capacity / 100;
  aBatteryInfo->charging() = (chargingSrc == BATTERY_CHARGING_USB ||
                              chargingSrc == BATTERY_CHARGING_AC);
  aBatteryInfo->remainingTime() = dom::battery::kUnknownRemainingTime;
}

namespace {

/**
 * RAII class to help us remember to close file descriptors.
 */
const char *wakeLockFilename = "/sys/power/wake_lock";
const char *wakeUnlockFilename = "/sys/power/wake_unlock";

template<ssize_t n>
bool ReadFromFile(const char *filename, char (&buf)[n])
{
  int fd = open(filename, O_RDONLY);
  ScopedClose autoClose(fd);
  if (fd < 0) {
    HAL_LOG(("Unable to open file %s.", filename));
    return false;
  }

  ssize_t numRead = read(fd, buf, n);
  if (numRead < 0) {
    HAL_LOG(("Error reading from file %s.", filename));
    return false;
  }

  buf[PR_MIN(numRead, n - 1)] = '\0';
  return true;
}

void WriteToFile(const char *filename, const char *toWrite)
{
  int fd = open(filename, O_WRONLY);
  ScopedClose autoClose(fd);
  if (fd < 0) {
    HAL_LOG(("Unable to open file %s.", filename));
    return;
  }

  if (write(fd, toWrite, strlen(toWrite)) < 0) {
    HAL_LOG(("Unable to write to file %s.", filename));
    return;
  }
}

// We can write to screenEnabledFilename to enable/disable the screen, but when
// we read, we always get "mem"!  So we have to keep track ourselves whether
// the screen is on or not.
bool sScreenEnabled = true;

// We can read wakeLockFilename to find out whether the cpu wake lock
// is already acquired, but reading and parsing it is a lot more work
// than tracking it ourselves, and it won't be accurate anyway (kernel
// internal wake locks aren't counted here.)
bool sCpuSleepAllowed = true;

} // anonymous namespace

bool
GetScreenEnabled()
{
  return sScreenEnabled;
}

void
SetScreenEnabled(bool enabled)
{
  set_screen_state(enabled);
  sScreenEnabled = enabled;
}

double
GetScreenBrightness()
{
  hal::LightConfiguration aConfig;
  hal::LightType light = hal::eHalLightID_Backlight;

  hal::GetLight(light, &aConfig);
  // backlight is brightness only, so using one of the RGB elements as value.
  int brightness = aConfig.color() & 0xFF;
  return brightness / 255.0;
}

void
SetScreenBrightness(double brightness)
{
  // Don't use De Morgan's law to push the ! into this expression; we want to
  // catch NaN too.
  if (!(0 <= brightness && brightness <= 1)) {
    HAL_LOG(("SetScreenBrightness: Dropping illegal brightness %f.",
             brightness));
    return;
  }

  // Convert the value in [0, 1] to an int between 0 and 255 and convert to a color
  // note that the high byte is FF, corresponding to the alpha channel.
  int val = static_cast<int>(round(brightness * 255));
  uint32_t color = (0xff<<24) + (val<<16) + (val<<8) + val;

  hal::LightConfiguration aConfig;
  aConfig.mode() = hal::eHalLightMode_User;
  aConfig.flash() = hal::eHalLightFlash_None;
  aConfig.flashOnMS() = aConfig.flashOffMS() = 0;
  aConfig.color() = color;
  hal::SetLight(hal::eHalLightID_Backlight, aConfig);
  hal::SetLight(hal::eHalLightID_Buttons, aConfig);
}

bool
GetCpuSleepAllowed()
{
  return sCpuSleepAllowed;
}

void
SetCpuSleepAllowed(bool aAllowed)
{
  WriteToFile(aAllowed ? wakeUnlockFilename : wakeLockFilename, "gecko");
  sCpuSleepAllowed = aAllowed;
}

static light_device_t* sLights[hal::eHalLightID_Count];	// will be initialized to NULL

light_device_t* GetDevice(hw_module_t* module, char const* name)
{
  int err;
  hw_device_t* device;
  err = module->methods->open(module, name, &device);
  if (err == 0) {
    return (light_device_t*)device;
  } else {
    return NULL;
  }
}

void
InitLights()
{
  // assume that if backlight is NULL, nothing has been set yet
  // if this is not true, the initialization will occur everytime a light is read or set!
  if (!sLights[hal::eHalLightID_Backlight]) {
    int err;
    hw_module_t* module;

    err = hw_get_module(LIGHTS_HARDWARE_MODULE_ID, (hw_module_t const**)&module);
    if (err == 0) {
      sLights[hal::eHalLightID_Backlight]
             = GetDevice(module, LIGHT_ID_BACKLIGHT);
      sLights[hal::eHalLightID_Keyboard]
             = GetDevice(module, LIGHT_ID_KEYBOARD);
      sLights[hal::eHalLightID_Buttons]
             = GetDevice(module, LIGHT_ID_BUTTONS);
      sLights[hal::eHalLightID_Battery]
             = GetDevice(module, LIGHT_ID_BATTERY);
      sLights[hal::eHalLightID_Notifications]
             = GetDevice(module, LIGHT_ID_NOTIFICATIONS);
      sLights[hal::eHalLightID_Attention]
             = GetDevice(module, LIGHT_ID_ATTENTION);
      sLights[hal::eHalLightID_Bluetooth]
             = GetDevice(module, LIGHT_ID_BLUETOOTH);
      sLights[hal::eHalLightID_Wifi]
             = GetDevice(module, LIGHT_ID_WIFI);
        }
    }
}

/**
 * The state last set for the lights until liblights supports
 * getting the light state.
 */
static light_state_t sStoredLightState[hal::eHalLightID_Count];

bool
SetLight(hal::LightType light, const hal::LightConfiguration& aConfig)
{
  light_state_t state;

  InitLights();

  if (light < 0 || light >= hal::eHalLightID_Count || sLights[light] == NULL) {
    return false;
  }

  memset(&state, 0, sizeof(light_state_t));
  state.color = aConfig.color();
  state.flashMode = aConfig.flash();
  state.flashOnMS = aConfig.flashOnMS();
  state.flashOffMS = aConfig.flashOffMS();
  state.brightnessMode = aConfig.mode();

  sLights[light]->set_light(sLights[light], &state);
  sStoredLightState[light] = state;
  return true;
}

bool
GetLight(hal::LightType light, hal::LightConfiguration* aConfig)
{
  light_state_t state;

#ifdef HAVEGETLIGHT
  InitLights();
#endif

  if (light < 0 || light >= hal::eHalLightID_Count || sLights[light] == NULL) {
    return false;
  }

  memset(&state, 0, sizeof(light_state_t));

#ifdef HAVEGETLIGHT
  sLights[light]->get_light(sLights[light], &state);
#else
  state = sStoredLightState[light];
#endif

  aConfig->light() = light;
  aConfig->color() = state.color;
  aConfig->flash() = hal::FlashMode(state.flashMode);
  aConfig->flashOnMS() = state.flashOnMS;
  aConfig->flashOffMS() = state.flashOffMS;
  aConfig->mode() = hal::LightMode(state.brightnessMode);

  return true;
}

/**
 * clock_settime() is not exposed through bionic. 
 * we define the new function to set system time.
 * The result is the same as using clock_settime() system call.     
 */
static int
sys_clock_settime(clockid_t clk_id, const struct timespec *tp)
{
  return syscall(__NR_clock_settime, clk_id, tp);
}

void 
AdjustSystemClock(int32_t aDeltaMilliseconds)
{
  if (aDeltaMilliseconds == 0) {
    return;
  }
  
  struct timespec now;
  
  // Preventing context switch before setting system clock 
  sched_yield();
  clock_gettime(CLOCK_REALTIME, &now);
  now.tv_sec += aDeltaMilliseconds/1000;
  now.tv_nsec += (aDeltaMilliseconds%1000)*NsecPerMsec;
  if (now.tv_nsec >= NsecPerSec)
  {
    now.tv_sec += 1;
    now.tv_nsec -= NsecPerSec;
  }

  if (now.tv_nsec < 0)
  {
    now.tv_nsec += NsecPerSec;
    now.tv_sec -= 1;  
  }
  // we need to have root privilege. 
  if (sys_clock_settime(CLOCK_REALTIME, &now) != 0) {
    NS_ERROR("sys_clock_settime failed");
    return;
  }
  
  hal::NotifySystemTimeChange(hal::SYS_TIME_CHANGE_CLOCK);
}

bool
IsSameTimeZone(const nsCString& aTimezoneSpec)
{
  char timezone[32];
  property_get("persist.sys.timezone", timezone, "");
  return aTimezoneSpec.EqualsASCII(timezone);
}

void 
SetTimezone(const nsCString& aTimezoneSpec)
{ 
  if (IsSameTimeZone(aTimezoneSpec)) {
    return;
  }
  
  property_set("persist.sys.timezone", aTimezoneSpec.get());
  // this function is automatically called by the other time conversion 
  // functions that depend on the timezone. To be safe, we call it manually.  
  tzset();
  hal::NotifySystemTimeChange(hal::SYS_TIME_CHANGE_TZ);
}

// Nothing to do here.  Gonk widgetry always listens for screen
// orientation changes.
void
EnableScreenConfigurationNotifications()
{
}

void
DisableScreenConfigurationNotifications()
{
}

void
GetCurrentScreenConfiguration(hal::ScreenConfiguration* aScreenConfiguration)
{
  *aScreenConfiguration = nsScreenGonk::GetConfiguration();
}

bool
LockScreenOrientation(const dom::ScreenOrientation& aOrientation)
{
  return OrientationObserver::GetInstance()->LockScreenOrientation(aOrientation);
}

void
UnlockScreenOrientation()
{
  OrientationObserver::GetInstance()->UnlockScreenOrientation();
}


static pthread_t sAlarmFireWatcherThread;

// If |sAlarmData| is non-null, it's owned by the watcher thread.
typedef struct AlarmData {

public:
  AlarmData(int aFd) : mFd(aFd), mGeneration(sNextGeneration++), mShuttingDown(false) {}
  ScopedClose mFd;
  int mGeneration;
  bool mShuttingDown;

  static int sNextGeneration;

} AlarmData;

int AlarmData::sNextGeneration = 0;

AlarmData* sAlarmData = NULL;

class AlarmFiredEvent : public nsRunnable {

public:
  AlarmFiredEvent(int aGeneration) : mGeneration(aGeneration) {}

  NS_IMETHOD Run() {
    // Guard against spurious notifications caused by an alarm firing
    // concurrently with it being disabled.
    if (sAlarmData && !sAlarmData->mShuttingDown && mGeneration == sAlarmData->mGeneration) {
      hal::NotifyAlarmFired();
    }

    return NS_OK;
  }

private:
  int mGeneration;
};

// Runs on alarm-watcher thread.
static void 
DestroyAlarmData(void* aData)
{
  AlarmData* alarmData = static_cast<AlarmData*>(aData);
  delete alarmData;
}

// Runs on alarm-watcher thread.
void ShutDownAlarm(int aSigno)
{
  if (aSigno == SIGUSR1) {
    sAlarmData->mShuttingDown = true;
  }
  return;
}

static void* 
WaitForAlarm(void* aData)
{
  pthread_cleanup_push(DestroyAlarmData, aData);

  AlarmData* alarmData = static_cast<AlarmData*>(aData);

  while (!alarmData->mShuttingDown) {
    int alarmTypeFlags = 0;

    // ALARM_WAIT apparently will block even if an alarm hasn't been
    // programmed, although this behavior doesn't seem to be
    // documented.  We rely on that here to avoid spinning the CPU
    // while awaiting an alarm to be programmed.
    do {
      alarmTypeFlags = ioctl(alarmData->mFd, ANDROID_ALARM_WAIT);
    } while (alarmTypeFlags < 0 && errno == EINTR && !alarmData->mShuttingDown);

    if (!alarmData->mShuttingDown && 
        alarmTypeFlags >= 0 && (alarmTypeFlags & ANDROID_ALARM_RTC_WAKEUP_MASK)) {
      NS_DispatchToMainThread(new AlarmFiredEvent(alarmData->mGeneration));
    }
  }

  pthread_cleanup_pop(1);
  return NULL;
}

bool
EnableAlarm()
{
  MOZ_ASSERT(!sAlarmData);

  int alarmFd = open("/dev/alarm", O_RDWR);
  if (alarmFd < 0) {
    HAL_LOG(("Failed to open alarm device: %s.", strerror(errno)));
    return false;
  }

  nsAutoPtr<AlarmData> alarmData(new AlarmData(alarmFd));

  struct sigaction actions;
  memset(&actions, 0, sizeof(actions));
  sigemptyset(&actions.sa_mask);
  actions.sa_flags = 0;
  actions.sa_handler = ShutDownAlarm;
  if (sigaction(SIGUSR1, &actions, NULL)) {
    HAL_LOG(("Failed to set SIGUSR1 signal for alarm-watcher thread."));
    return false;
  }

  pthread_attr_t attr;
  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

  int status = pthread_create(&sAlarmFireWatcherThread, &attr, WaitForAlarm, alarmData.get());
  if (status) {
    alarmData = NULL;
    HAL_LOG(("Failed to create alarm watcher thread. Status: %d.", status));
    return false;
  }

  pthread_attr_destroy(&attr);

  // The thread owns this now.  We only hold a pointer.
  sAlarmData = alarmData.forget();
  return true;
}

void
DisableAlarm()
{
  MOZ_ASSERT(sAlarmData);

  // NB: this must happen-before the thread cancellation.
  sAlarmData = NULL;

  // The cancel will interrupt the thread and destroy it, freeing the
  // data pointed at by sAlarmData.
  DebugOnly<int> err = pthread_kill(sAlarmFireWatcherThread, SIGUSR1);
  MOZ_ASSERT(!err);
}

bool
SetAlarm(PRInt32 aSeconds, PRInt32 aNanoseconds)
{
  if (!sAlarmData) {
    HAL_LOG(("We should have enabled the alarm."));
    return false;
  }

  struct timespec ts;
  ts.tv_sec = aSeconds;
  ts.tv_nsec = aNanoseconds;

  // currently we only support RTC wakeup alarm type
  const int result = ioctl(sAlarmData->mFd, ANDROID_ALARM_SET(ANDROID_ALARM_RTC_WAKEUP), &ts);

  if (result < 0) {
    HAL_LOG(("Unable to set alarm: %s.", strerror(errno)));
    return false;
  }

  return true;
}

void
SetProcessPriority(int aPid, ProcessPriority aPriority)
{
  HAL_LOG(("SetProcessPriority(pid=%d, priority=%d)", aPid, aPriority));

  const char* priorityStr = NULL;
  switch (aPriority) {
  case PROCESS_PRIORITY_BACKGROUND:
    priorityStr = "background";
    break;
  case PROCESS_PRIORITY_FOREGROUND:
    priorityStr = "foreground";
    break;
  case PROCESS_PRIORITY_MASTER:
    priorityStr = "master";
    break;
  default:
    MOZ_NOT_REACHED();
  }

  // Notice that you can disable oom_adj and renice by deleting the prefs
  // hal.processPriorityManager{foreground,background,master}{OomAdjust,Nice}.

  PRInt32 oomAdj = 0;
  nsresult rv = Preferences::GetInt(nsPrintfCString(
    "hal.processPriorityManager.gonk.%sOomAdjust", priorityStr).get(), &oomAdj);
  if (NS_SUCCEEDED(rv)) {
    HAL_LOG(("Setting oom_adj for pid %d to %d", aPid, oomAdj));
    WriteToFile(nsPrintfCString("/proc/%d/oom_adj", aPid).get(),
                nsPrintfCString("%d", oomAdj).get());
  }

  PRInt32 nice = 0;
  rv = Preferences::GetInt(nsPrintfCString(
    "hal.processPriorityManager.gonk.%sNice", priorityStr).get(), &nice);
  if (NS_SUCCEEDED(rv)) {
    HAL_LOG(("Setting nice for pid %d to %d", aPid, nice));

    int success = setpriority(PRIO_PROCESS, aPid, nice);
    if (success != 0) {
      HAL_LOG(("Failed to set nice for pid %d to %d", aPid, nice));
    }
  }
}

} // hal_impl
} // mozilla