Deadlock in Library::writeBookmarksToFile()

[veloman-yunkan]

#636 introduced a deadlock in Library::writeBookmarksToFile().

Library::writeBookmarksToFile() calls LibXMLDumper::dumpLibXMLBookmark() under a lock

libkiwix/src/library.cpp

Lines 274 to 283 in 01ac0b2

	bool Library::writeBookmarksToFile(const std::string& path) const
	{
	LibXMLDumper dumper(this);
	std::string xml;
	{
	std::lock_guard<std::mutex> lock(m_mutex);
	xml = dumper.dumpLibXMLBookmark();
	};
	return writeTextFile(path, xml);
	}

LibXMLDumper::dumpLibXMLBookmark() calls the thread-safe function Library::getBookmarks() which is protected by the same mutex:

libkiwix/src/libxml_dumper.cpp

Lines 127 to 140 in 01ac0b2

	std::string LibXMLDumper::dumpLibXMLBookmark()
	{
	pugi::xml_document doc;
	/* Add the library node */
	pugi::xml_node bookmarksNode = doc.append_child("bookmarks");
	if (library) {
	for (auto& bookmark: library->getBookmarks()) {
	handleBookmark(bookmark, bookmarksNode);
	}
	}
	return nodeToString(bookmarksNode);
	}

libkiwix/src/library.cpp

Lines 344 to 358 in 01ac0b2

	const std::vector<kiwix::Bookmark> Library::getBookmarks(bool onlyValidBookmarks) const
	{
	if (!onlyValidBookmarks) {
	return m_bookmarks;
	}
	std::vector<kiwix::Bookmark> validBookmarks;
	auto booksId = getBooksIds();
	std::lock_guard<std::mutex> lock(m_mutex);
	for(auto& bookmark:m_bookmarks) {
	if (std::find(booksId.begin(), booksId.end(), bookmark.getBookId()) != booksId.end()) {
	validBookmarks.push_back(bookmark);
	}
	}
	return validBookmarks;
	}