mozglue/misc/ConditionVariable_windows.cpp
author Gerald Squelart <gsquelart@mozilla.com>
Thu, 04 Jul 2019 04:38:16 +0000
changeset 481213 8fed7bc35767fdfab4bac0908ae9b21c08f49e1f
parent 454520 5f4630838d46dd81dadb13220a4af0da9e23a619
permissions -rw-r--r--
Bug 1559000 - mozglue's AutoProfilerLabel doesn't need to know about ProfilingStack - r=mstange `ProfilingStack*` happens to be the information that the current Gecko Profiler entry function wants to forward to the exit function, but AutoProfilerLabel does not really need to know about that. Changing it to `void*`, so that we can later use different entry/exit functions that use different context types. Differential Revision: https://phabricator.services.mozilla.com/D34806

/* -*- 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 "mozilla/Assertions.h"

#include <float.h>
#include <intrin.h>
#include <stdlib.h>
#include <windows.h>

#include "mozilla/PlatformConditionVariable.h"
#include "mozilla/PlatformMutex.h"
#include "MutexPlatformData_windows.h"

// Some versions of the Windows SDK have a bug where some interlocked functions
// are not redefined as compiler intrinsics. Fix that for the interlocked
// functions that are used in this file.
#if defined(_MSC_VER) && !defined(InterlockedExchangeAdd)
#  define InterlockedExchangeAdd(addend, value) \
    _InterlockedExchangeAdd((volatile long*)(addend), (long)(value))
#endif

#if defined(_MSC_VER) && !defined(InterlockedIncrement)
#  define InterlockedIncrement(addend) \
    _InterlockedIncrement((volatile long*)(addend))
#endif

// Wrapper for native condition variable APIs.
struct mozilla::detail::ConditionVariableImpl::PlatformData {
  CONDITION_VARIABLE cv_;
};

mozilla::detail::ConditionVariableImpl::ConditionVariableImpl() {
  InitializeConditionVariable(&platformData()->cv_);
}

void mozilla::detail::ConditionVariableImpl::notify_one() {
  WakeConditionVariable(&platformData()->cv_);
}

void mozilla::detail::ConditionVariableImpl::notify_all() {
  WakeAllConditionVariable(&platformData()->cv_);
}

void mozilla::detail::ConditionVariableImpl::wait(MutexImpl& lock) {
  SRWLOCK* srwlock = &lock.platformData()->lock;
  bool r =
      SleepConditionVariableSRW(&platformData()->cv_, srwlock, INFINITE, 0);
  MOZ_RELEASE_ASSERT(r);
}

mozilla::CVStatus mozilla::detail::ConditionVariableImpl::wait_for(
    MutexImpl& lock, const mozilla::TimeDuration& rel_time) {
  if (rel_time == mozilla::TimeDuration::Forever()) {
    wait(lock);
    return CVStatus::NoTimeout;
  }

  SRWLOCK* srwlock = &lock.platformData()->lock;

  // Note that DWORD is unsigned, so we have to be careful to clamp at 0. If
  // rel_time is Forever, then ToMilliseconds is +inf, which evaluates as
  // greater than UINT32_MAX, resulting in the correct INFINITE wait. We also
  // don't want to round sub-millisecond waits to 0, as that wastes energy (see
  // bug 1437167 comment 6), so we instead round submillisecond waits to 1ms.
  double msecd = rel_time.ToMilliseconds();
  DWORD msec;
  if (msecd < 0.0) {
    msec = 0;
  } else if (msecd > UINT32_MAX) {
    msec = INFINITE;
  } else {
    msec = static_cast<DWORD>(msecd);
    // Round submillisecond waits to 1ms.
    if (msec == 0 && !rel_time.IsZero()) {
      msec = 1;
    }
  }

  BOOL r = SleepConditionVariableSRW(&platformData()->cv_, srwlock, msec, 0);
  if (r) return CVStatus::NoTimeout;
  MOZ_RELEASE_ASSERT(GetLastError() == ERROR_TIMEOUT);
  return CVStatus::Timeout;
}

mozilla::detail::ConditionVariableImpl::~ConditionVariableImpl() {
  // Native condition variables don't require cleanup.
}

inline mozilla::detail::ConditionVariableImpl::PlatformData*
mozilla::detail::ConditionVariableImpl::platformData() {
  static_assert(sizeof platformData_ >= sizeof(PlatformData),
                "platformData_ is too small");
  return reinterpret_cast<PlatformData*>(platformData_);
}