ipc/glue/CrossProcessSemaphore_mach.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 "CrossProcessSemaphore.h"
   8 #include "nsDebug.h"
   9 #include "nsISupportsImpl.h"
  10 #include <mach/mach_time.h>
  11
  12 static const uint64_t kNsPerUs = 1000;
  13 static const uint64_t kNsPerSec = 1000000000;
  14
  15 namespace mozilla {
  16
  17 /* static */
  18 CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*,
  19                                                      uint32_t aInitialValue) {
  20   semaphore_t sem = SEMAPHORE_NULL;
  21   if (semaphore_create(mach_task_self(), &sem, SYNC_POLICY_FIFO,
  22                        aInitialValue) == KERN_SUCCESS &&
  23       sem != SEMAPHORE_NULL) {
  24     return new CrossProcessSemaphore(CrossProcessSemaphoreHandle(sem));
  25   }
  26   return nullptr;
  27 }
  28
  29 /* static */
  30 CrossProcessSemaphore* CrossProcessSemaphore::Create(
  31     CrossProcessSemaphoreHandle aHandle) {
  32   if (!aHandle) {
  33     return nullptr;
  34   }
  35   return new CrossProcessSemaphore(std::move(aHandle));
  36 }
  37
  38 CrossProcessSemaphore::CrossProcessSemaphore(
  39     CrossProcessSemaphoreHandle aSemaphore)
  40     : mSemaphore(std::move(aSemaphore)) {
  41   MOZ_COUNT_CTOR(CrossProcessSemaphore);
  42 }
  43
  44 CrossProcessSemaphore::~CrossProcessSemaphore() {
  45   MOZ_ASSERT(mSemaphore, "Improper construction of semaphore or double free.");
  46   MOZ_COUNT_DTOR(CrossProcessSemaphore);
  47 }
  48
  49 bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
  50   MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
  51   int kr = KERN_OPERATION_TIMED_OUT;
  52   // semaphore_(timed)wait may be interrupted by KERN_ABORTED. Carefully restart
  53   // the wait until it either succeeds or times out.
  54   if (aWaitTime.isNothing()) {
  55     do {
  56       kr = semaphore_wait(mSemaphore.get());
  57     } while (kr == KERN_ABORTED);
  58   } else {
  59     mach_timebase_info_data_t tb;
  60     if (mach_timebase_info(&tb) != KERN_SUCCESS) {
  61       return false;
  62     }
  63     uint64_t now = (mach_absolute_time() * tb.numer) / tb.denom;
  64     uint64_t deadline = now + uint64_t(kNsPerUs * aWaitTime->ToMicroseconds());
  65     while (now <= deadline) {
  66       uint64_t ns = deadline - now;
  67       mach_timespec_t ts;
  68       ts.tv_sec = ns / kNsPerSec;
  69       ts.tv_nsec = ns % kNsPerSec;
  70       kr = semaphore_timedwait(mSemaphore.get(), ts);
  71       if (kr != KERN_ABORTED) {
  72         break;
  73       }
  74       now = (mach_absolute_time() * tb.numer) / tb.denom;
  75     }
  76   }
  77   return kr == KERN_SUCCESS;
  78 }
  79
  80 void CrossProcessSemaphore::Signal() {
  81   MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
  82   semaphore_signal(mSemaphore.get());
  83 }
  84
  85 CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
  86   // Transfer the mach port backing the semaphore.
  87   return mozilla::RetainMachSendRight(mSemaphore.get());
  88 }
  89
  90 void CrossProcessSemaphore::CloseHandle() {}
  91
  92 }  // namespace mozilla