mozglue/misc/ConditionVariable_windows.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/Assertions.h"
   8
   9 #include <float.h>
  10 #include <intrin.h>
  11 #include <stdlib.h>
  12 #include <windows.h>
  13
  14 #include "mozilla/PlatformConditionVariable.h"
  15 #include "mozilla/PlatformMutex.h"
  16 #include "MutexPlatformData_windows.h"
  17
  18 // Some versions of the Windows SDK have a bug where some interlocked functions
  19 // are not redefined as compiler intrinsics. Fix that for the interlocked
  20 // functions that are used in this file.
  21 #if defined(_MSC_VER) && !defined(InterlockedExchangeAdd)
  22 #  define InterlockedExchangeAdd(addend, value) \
  23     _InterlockedExchangeAdd((volatile long*)(addend), (long)(value))
  24 #endif
  25
  26 #if defined(_MSC_VER) && !defined(InterlockedIncrement)
  27 #  define InterlockedIncrement(addend) \
  28     _InterlockedIncrement((volatile long*)(addend))
  29 #endif
  30
  31 // Wrapper for native condition variable APIs.
  32 struct mozilla::detail::ConditionVariableImpl::PlatformData {
  33   CONDITION_VARIABLE cv_;
  34 };
  35
  36 mozilla::detail::ConditionVariableImpl::ConditionVariableImpl() {
  37   InitializeConditionVariable(&platformData()->cv_);
  38 }
  39
  40 void mozilla::detail::ConditionVariableImpl::notify_one() {
  41   WakeConditionVariable(&platformData()->cv_);
  42 }
  43
  44 void mozilla::detail::ConditionVariableImpl::notify_all() {
  45   WakeAllConditionVariable(&platformData()->cv_);
  46 }
  47
  48 void mozilla::detail::ConditionVariableImpl::wait(MutexImpl& lock) {
  49   SRWLOCK* srwlock = &lock.platformData()->lock;
  50   bool r =
  51       SleepConditionVariableSRW(&platformData()->cv_, srwlock, INFINITE, 0);
  52   MOZ_RELEASE_ASSERT(r);
  53 }
  54
  55 mozilla::CVStatus mozilla::detail::ConditionVariableImpl::wait_for(
  56     MutexImpl& lock, const mozilla::TimeDuration& rel_time) {
  57   if (rel_time == mozilla::TimeDuration::Forever()) {
  58     wait(lock);
  59     return CVStatus::NoTimeout;
  60   }
  61
  62   SRWLOCK* srwlock = &lock.platformData()->lock;
  63
  64   // Note that DWORD is unsigned, so we have to be careful to clamp at 0. If
  65   // rel_time is Forever, then ToMilliseconds is +inf, which evaluates as
  66   // greater than UINT32_MAX, resulting in the correct INFINITE wait. We also
  67   // don't want to round sub-millisecond waits to 0, as that wastes energy (see
  68   // bug 1437167 comment 6), so we instead round submillisecond waits to 1ms.
  69   double msecd = rel_time.ToMilliseconds();
  70   DWORD msec;
  71   if (msecd < 0.0) {
  72     msec = 0;
  73   } else if (msecd > UINT32_MAX) {
  74     msec = INFINITE;
  75   } else {
  76     msec = static_cast<DWORD>(msecd);
  77     // Round submillisecond waits to 1ms.
  78     if (msec == 0 && !rel_time.IsZero()) {
  79       msec = 1;
  80     }
  81   }
  82
  83   BOOL r = SleepConditionVariableSRW(&platformData()->cv_, srwlock, msec, 0);
  84   if (r) return CVStatus::NoTimeout;
  85   MOZ_RELEASE_ASSERT(GetLastError() == ERROR_TIMEOUT);
  86   return CVStatus::Timeout;
  87 }
  88
  89 mozilla::detail::ConditionVariableImpl::~ConditionVariableImpl() {
  90   // Native condition variables don't require cleanup.
  91 }
  92
  93 inline mozilla::detail::ConditionVariableImpl::PlatformData*
  94 mozilla::detail::ConditionVariableImpl::platformData() {
  95   static_assert(sizeof platformData_ >= sizeof(PlatformData),
  96                 "platformData_ is too small");
  97   return reinterpret_cast<PlatformData*>(platformData_);
  98 }