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Proper fix for skipped file downloads due to race condition

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Properly fixes the skipped file downloads due to race condition caused by trying create same directory from multiple threads at the same time.
4c480465b3 fixed the issue by having additional check to see if the directory exists after boost::filesystem::create_directories() returned false.
This fix uses mutex to make sure only one thread at a time can check if the directory exists and create it
This commit is contained in:
Sude 2016-11-04 09:52:35 +02:00
parent 4c480465b3
commit 0b3a6643c6
1 changed files with 16 additions and 8 deletions
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24
src/downloader.cpp
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@ -34,6 +34,7 @@ std::vector<DownloadInfo> vDownloadInfo;
ThreadSafeQueue<gameFile> dlQueue; ThreadSafeQueue<gameFile> dlQueue;
ThreadSafeQueue<Message> msgQueue; ThreadSafeQueue<Message> msgQueue;
ThreadSafeQueue<gameFile> createXMLQueue; ThreadSafeQueue<gameFile> createXMLQueue;
std::mutex mtx_create_directories; // Mutex for creating directories in Downloader::processDownloadQueue
Downloader::Downloader(Config &conf) Downloader::Downloader(Config &conf)
{ {
@ -2956,26 +2957,31 @@ void Downloader::processDownloadQueue(Config conf, const unsigned int& tid)
msgQueue.push(Message("Begin download: " + filepath.filename().string(), MSGTYPE_INFO, msg_prefix)); msgQueue.push(Message("Begin download: " + filepath.filename().string(), MSGTYPE_INFO, msg_prefix));
// Check that directory exists and create subdirectories // Check that directory exists and create subdirectories
mtx_create_directories.lock(); // Use mutex to avoid possible race conditions
if (boost::filesystem::exists(directory)) if (boost::filesystem::exists(directory))
{ {
if (!boost::filesystem::is_directory(directory)) if (!boost::filesystem::is_directory(directory))
{ {
mtx_create_directories.unlock();
msgQueue.push(Message(directory.string() + " is not directory, skipping file (" + filepath.filename().string() + ")", MSGTYPE_WARNING, msg_prefix)); msgQueue.push(Message(directory.string() + " is not directory, skipping file (" + filepath.filename().string() + ")", MSGTYPE_WARNING, msg_prefix));
continue; continue;
} }
else
{
mtx_create_directories.unlock();
}
} }
else else
{ {
if (!boost::filesystem::create_directories(directory)) if (!boost::filesystem::create_directories(directory))
{ {
/* Multiple threads could have tried to create the directory at the same time because they detected that the directory didn't exist at the time mtx_create_directories.unlock();
* boost::filesystem::create_directories() could have returned false because of this race condition so we have to check again if directory exists */ msgQueue.push(Message("Failed to create directory (" + directory.string() + "), skipping file (" + filepath.filename().string() + ")", MSGTYPE_ERROR, msg_prefix));
if (!boost::filesystem::exists(directory)) continue;
{ }
// Failed to create directory and another thread hasn't created it either. Print error and skip the file download. else
msgQueue.push(Message("Failed to create directory (" + directory.string() + "), skipping file (" + filepath.filename().string() + ")", MSGTYPE_ERROR, msg_prefix)); {
continue; mtx_create_directories.unlock();
}
} }
} }
@ -3042,6 +3048,7 @@ void Downloader::processDownloadQueue(Config conf, const unsigned int& tid)
{ {
// Check that directory exists and create subdirectories // Check that directory exists and create subdirectories
boost::filesystem::path path = xml_directory; boost::filesystem::path path = xml_directory;
mtx_create_directories.lock(); // Use mutex to avoid race conditions
if (boost::filesystem::exists(path)) if (boost::filesystem::exists(path))
{ {
if (!boost::filesystem::is_directory(path)) if (!boost::filesystem::is_directory(path))
@ -3056,6 +3063,7 @@ void Downloader::processDownloadQueue(Config conf, const unsigned int& tid)
msgQueue.push(Message("Failed to create directory: " + path.string(), MSGTYPE_ERROR, msg_prefix)); msgQueue.push(Message("Failed to create directory: " + path.string(), MSGTYPE_ERROR, msg_prefix));
} }
} }
mtx_create_directories.unlock();
std::ofstream ofs(local_xml_file.string().c_str()); std::ofstream ofs(local_xml_file.string().c_str());
if (ofs) if (ofs)
{ {