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Fix race condition in QAlertDispatcher

Browse Source 
It was possible that QAlertDispatcher::dispatch() could access (lock)
mutex that was destroyed by main thread. Fix this by moving mutex into a
tag.
This commit is contained in:
Ivan Sorokin 2014-10-12 12:01:30 +04:00
parent 333978f1ff
commit b995a9d75e
2 changed files with 25 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
src/qtlibtorrent/alertdispatcher.cpp
View File

@ -35,10 +35,21 @@
const size_t DEFAULT_ALERTS_CAPACITY = 32; const size_t DEFAULT_ALERTS_CAPACITY = 32;
struct QAlertDispatcher::Tag {
Tag(QAlertDispatcher* dispatcher);
QAlertDispatcher* dispatcher;
QMutex alerts_mutex;
};
QAlertDispatcher::Tag::Tag(QAlertDispatcher* dispatcher)
: dispatcher(dispatcher)
{}
QAlertDispatcher::QAlertDispatcher(libtorrent::session *session, QObject* parent) QAlertDispatcher::QAlertDispatcher(libtorrent::session *session, QObject* parent)
: QObject(parent) : QObject(parent)
, m_session(session) , m_session(session)
, current_tag(new QAtomicPointer<QAlertDispatcher>(this)) , current_tag(new Tag(this))
, event_posted(false) , event_posted(false)
{ {
alerts.reserve(DEFAULT_ALERTS_CAPACITY); alerts.reserve(DEFAULT_ALERTS_CAPACITY);
@ -54,8 +65,8 @@ QAlertDispatcher::~QAlertDispatcher() {
// with invalid tag it simply discard an alert. // with invalid tag it simply discard an alert.
{ {
QMutexLocker lock(&alerts_mutex); QMutexLocker lock(&current_tag->alerts_mutex);
*current_tag = 0; current_tag->dispatcher = 0;
current_tag.clear(); current_tag.clear();
} }
@ -67,7 +78,7 @@ void QAlertDispatcher::getPendingAlertsNoWait(std::vector<libtorrent::alert*>& o
Q_ASSERT(out.empty()); Q_ASSERT(out.empty());
out.reserve(DEFAULT_ALERTS_CAPACITY); out.reserve(DEFAULT_ALERTS_CAPACITY);
QMutexLocker lock(&alerts_mutex); QMutexLocker lock(&current_tag->alerts_mutex);
alerts.swap(out); alerts.swap(out);
event_posted = false; event_posted = false;
} }
@ -76,34 +87,22 @@ void QAlertDispatcher::getPendingAlerts(std::vector<libtorrent::alert*>& out, un
Q_ASSERT(out.empty()); Q_ASSERT(out.empty());
out.reserve(DEFAULT_ALERTS_CAPACITY); out.reserve(DEFAULT_ALERTS_CAPACITY);
QMutexLocker lock(&alerts_mutex); QMutexLocker lock(&current_tag->alerts_mutex);
while (alerts.empty()) while (alerts.empty())
alerts_condvar.wait(&alerts_mutex, time); alerts_condvar.wait(&current_tag->alerts_mutex, time);
alerts.swap(out); alerts.swap(out);
event_posted = false; event_posted = false;
} }
void QAlertDispatcher::dispatch(QSharedPointer<QAtomicPointer<QAlertDispatcher> > tag, void QAlertDispatcher::dispatch(QSharedPointer<Tag> tag,
std::auto_ptr<libtorrent::alert> alert_ptr) { std::auto_ptr<libtorrent::alert> alert_ptr) {
#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)) QMutexLocker lock(&(tag->alerts_mutex));
QAlertDispatcher* that = tag->loadAcquire(); QAlertDispatcher* that = tag->dispatcher;
#else
QAlertDispatcher* that = *tag;
#endif
if (!that) if (!that)
return; return;
QMutexLocker lock(&(that->alerts_mutex));
#if (QT_VERSION >= QT_VERSION_CHECK(5, 0, 0))
if (!tag->load())
#else
if (!*tag)
#endif
return;
bool was_empty = that->alerts.empty(); bool was_empty = that->alerts.empty();
that->alerts.push_back(alert_ptr.get()); that->alerts.push_back(alert_ptr.get());
@ -127,7 +126,7 @@ void QAlertDispatcher::enqueueToMainThread() {
void QAlertDispatcher::deliverSignal() { void QAlertDispatcher::deliverSignal() {
emit alertsReceived(); emit alertsReceived();
QMutexLocker lock(&alerts_mutex); QMutexLocker lock(&current_tag->alerts_mutex);
event_posted = false; event_posted = false;
if (!alerts.empty()) if (!alerts.empty())

7
src/qtlibtorrent/alertdispatcher.h
View File

@ -42,6 +42,8 @@ class QAlertDispatcher : public QObject {
Q_OBJECT Q_OBJECT
Q_DISABLE_COPY(QAlertDispatcher) Q_DISABLE_COPY(QAlertDispatcher)
struct Tag;
public: public:
QAlertDispatcher(libtorrent::session *session, QObject* parent); QAlertDispatcher(libtorrent::session *session, QObject* parent);
~QAlertDispatcher(); ~QAlertDispatcher();
@ -53,7 +55,7 @@ signals:
void alertsReceived(); void alertsReceived();
private: private:
static void dispatch(QSharedPointer<QAtomicPointer<QAlertDispatcher> >, static void dispatch(QSharedPointer<Tag>,
std::auto_ptr<libtorrent::alert>); std::auto_ptr<libtorrent::alert>);
void enqueueToMainThread(); void enqueueToMainThread();
@ -62,10 +64,9 @@ private slots:
private: private:
libtorrent::session *m_session; libtorrent::session *m_session;
QMutex alerts_mutex;
QWaitCondition alerts_condvar; QWaitCondition alerts_condvar;
std::vector<libtorrent::alert*> alerts; std::vector<libtorrent::alert*> alerts;
QSharedPointer<QAtomicPointer<QAlertDispatcher> > current_tag; QSharedPointer<Tag> current_tag;
bool event_posted; bool event_posted;
}; };