toolkit/mozapps/defaultagent/WindowsMutex.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   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/Logging.h"
   8
   9 #include "WindowsMutex.h"
  10
  11 namespace mozilla::default_agent {
  12
  13 using mozilla::LogLevel;
  14
  15 static LazyLogModule gWindowsMutexLog("WindowsMutex");
  16
  17 NS_IMPL_ISUPPORTS(WindowsMutexFactory, nsIWindowsMutexFactory)
  18
  19 NS_IMETHODIMP
  20 WindowsMutexFactory::CreateMutex(const nsAString& aName,
  21                                  nsIWindowsMutex** aWindowsMutex) {
  22   nsAutoHandle mutex;
  23   auto name = PromiseFlatString(aName);
  24
  25   mutex.own(CreateMutexW(nullptr, FALSE, name.get()));
  26   if (mutex.get() == nullptr) {
  27     MOZ_LOG(gWindowsMutexLog, LogLevel::Error,
  28             ("Couldn't open mutex \"%s\": %#lX",
  29              NS_ConvertUTF16toUTF8(name).get(), GetLastError()));
  30     return NS_ERROR_NOT_AVAILABLE;
  31   }
  32
  33   RefPtr<WindowsMutex> nsMutex = new WindowsMutex(name, mutex);
  34   nsMutex.forget(aWindowsMutex);
  35   return NS_OK;
  36 }
  37
  38 WindowsMutex::WindowsMutex(const nsString& aName, nsAutoHandle& aMutex)
  39     : mName(NS_ConvertUTF16toUTF8(aName)), mLocked(false) {
  40   mMutex.steal(aMutex);
  41 }
  42
  43 WindowsMutex::~WindowsMutex() {
  44   Unlock();
  45   // nsAutoHandle will take care of closing the mutex's handle.
  46 }
  47
  48 NS_IMPL_ISUPPORTS(WindowsMutex, nsIWindowsMutex)
  49
  50 NS_IMETHODIMP
  51 WindowsMutex::TryLock() {
  52   // This object may be used on the main thread, so don't wait if it's
  53   // not signaled.
  54   DWORD mutexStatus = WaitForSingleObject(mMutex.get(), 0);
  55   if (mutexStatus == WAIT_OBJECT_0) {
  56     mLocked = true;
  57   } else if (mutexStatus == WAIT_TIMEOUT) {
  58     MOZ_LOG(gWindowsMutexLog, LogLevel::Warning,
  59             ("Timed out waiting for mutex \"%s\"", mName.get()));
  60   } else if (mutexStatus == WAIT_ABANDONED) {
  61     // This status code means that we are supposed to check our data for
  62     // consistency as the last locking process didn't signal intentional
  63     // unlocking which might indicate it crashed mid-operation. Current uses of
  64     // this `WindowsMutex` don't need to worry about corruption of the locked
  65     // object, if needed the `nsIWindowsMutex` interface should be extended.
  66     MOZ_LOG(gWindowsMutexLog, LogLevel::Warning,
  67             ("Found abandoned mutex \"%s\". Continuing...", mName.get()));
  68     mLocked = true;
  69   } else {
  70     // The only other documented status code is WAIT_FAILED. In the case that
  71     // we somehow get some other code, that is also an error.
  72     MOZ_LOG(gWindowsMutexLog, LogLevel::Error,
  73             ("Failed to wait on mutex: mName: %s, error %#lX", mName.get(),
  74              GetLastError()));
  75   }
  76   return mLocked ? NS_OK : NS_ERROR_NOT_AVAILABLE;
  77 }
  78
  79 NS_IMETHODIMP
  80 WindowsMutex::IsLocked(bool* aLocked) {
  81   *aLocked = mLocked;
  82   return NS_OK;
  83 }
  84
  85 NS_IMETHODIMP
  86 WindowsMutex::Unlock() {
  87   nsresult rv = NS_OK;
  88
  89   if (mLocked) {
  90     BOOL success = ReleaseMutex(mMutex.get());
  91     if (!success) {
  92       MOZ_LOG(gWindowsMutexLog, LogLevel::Error,
  93               ("Failed to release mutex \"%s\"", mName.get()));
  94       rv = NS_ERROR_UNEXPECTED;
  95     }
  96
  97     mLocked = false;
  98   }
  99
 100   return rv;
 101 }
 102
 103 }  // namespace mozilla::default_agent