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Fix crashes with libproxy+webkitgtk: it's not threadsafe 

I'm getting crashes in Akonadi processes due to libproxy. I don't have
direct evidence that this was caused by a threading condition, but it's
clear from the source code of libproxy that the plugins it runs for
expanding PAC scripts are not thread-safe. To overcome this problem, we
only run libproxy functions in one thread only.

 #0  0x00007f745f0ac1d8 in JSC::HeapTimer::timerDidFire() () at /usr/lib64/libjavascriptcoregtk-4.0.so.18
 #1  0x00007f745f0ac287 in  () at /usr/lib64/libjavascriptcoregtk-4.0.so.18
 #2  0x00007f748e5ae9c5 in g_main_context_dispatch () at /usr/lib64/libglib-2.0.so.0
 #3  0x00007f748e5aed88 in  () at /usr/lib64/libglib-2.0.so.0
 #4  0x00007f748e5aee1c in g_main_context_iteration () at /usr/lib64/libglib-2.0.so.0
 #5  0x00007f7494f4268f in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
 #6  0x00007f7494eeb35a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
 #7  0x00007f7494d1b31a in QThread::exec() () at /usr/lib64/libQt5Core.so.5
 #8  0x00007f7494d1fd2e in  () at /usr/lib64/libQt5Core.so.5
 #9  0x00007f74913174e7 in start_thread () at /lib64/libpthread.so.0

The pacrunner implementation of libproxy uses libdbus-1 which
(officially) is thread-safe, but experience tells that it has
problems. Since it is not running a JS engine, we don't need a thread,
but we do need to lock around it.

Change-Id: I84e45059a888497fb55ffffd14d2f638f21e807d
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
bb10
Thiago Macieira 2017-07-19 23:32:30 -07:00
parent 0f11fab6f7
commit db0585d63a
2 changed files with 120 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/network/kernel/kernel.pri
View File

@ -63,6 +63,6 @@ osx:SOURCES += kernel/qnetworkproxy_mac.cpp
else:win32:SOURCES += kernel/qnetworkproxy_win.cpp
else: qtConfig(libproxy) {
SOURCES += kernel/qnetworkproxy_libproxy.cpp
QMAKE_USE_PRIVATE += libproxy
QMAKE_USE_PRIVATE += libproxy libdl
}
else:SOURCES += kernel/qnetworkproxy_generic.cpp

143
src/network/kernel/qnetworkproxy_libproxy.cpp
View File

@ -1,6 +1,7 @@
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Copyright (C) 2017 Intel Corporation.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtNetwork module of the Qt Toolkit.
@ -42,57 +43,149 @@
#ifndef QT_NO_NETWORKPROXY
#include <QtCore/QByteArray>
#include <QtCore/QMutex>
#include <QtCore/QSemaphore>
#include <QtCore/QUrl>
#include <QtCore/private/qeventdispatcher_unix_p.h>
#include <QtCore/private/qthread_p.h>
#include <proxy.h>
#include <dlfcn.h>
QT_BEGIN_NAMESPACE
class QLibProxyWrapper
static bool isThreadingNeeded()
{
public:
QLibProxyWrapper()
: factory(px_proxy_factory_new())
{
if (!factory)
qWarning("libproxy initialization failed.");
}
// Try to guess if the libproxy we linked to is from the libproxy project
// or if it is from pacrunner. Neither library is thread-safe, but the one
// from libproxy is worse, since it may launch JS engines that don't take
// kindly to being executed from multiple threads (even if at different
// times). The pacrunner implementation doesn't suffer from this because
// the JS execution is out of process, in the pacrunner daemon.
~QLibProxyWrapper()
{
px_proxy_factory_free(factory);
}
void *sym;
#ifdef Q_CC_GNU
// Search for the mangled name of the virtual table of the pacrunner
// extension. Even if libproxy begins using -fvisibility=hidden, this
// symbol can't be hidden.
sym = dlsym(RTLD_DEFAULT, "_ZTVN8libproxy19pacrunner_extensionE");
#else
// The default libproxy one uses libmodman for its module management and
// leaks symbols because it doesn't use -fvisibility=hidden (as of
// v0.4.15).
sym = dlsym(RTLD_DEFAULT, "mm_info_ignore_hostname");
#endif
return sym != nullptr;
}
class QLibProxyWrapper : public QDaemonThread
{
Q_OBJECT
public:
QLibProxyWrapper();
~QLibProxyWrapper();
QList<QUrl> getProxies(const QUrl &url);
private:
pxProxyFactory *factory;
struct Data {
// we leave the conversion to/from QUrl to the calling thread
const char *url;
char **proxies;
QSemaphore replyReady;
};
void run() override;
pxProxyFactory *factory; // not subject to the mutex
QMutex mutex;
QSemaphore requestReady;
Data *request;
};
Q_GLOBAL_STATIC(QLibProxyWrapper, libProxyWrapper);
QLibProxyWrapper::QLibProxyWrapper()
{
if (isThreadingNeeded()) {
setEventDispatcher(new QEventDispatcherUNIX); // don't allow the Glib one
start();
} else {
factory = px_proxy_factory_new();
Q_CHECK_PTR(factory);
}
}
QLibProxyWrapper::~QLibProxyWrapper()
{
if (isRunning()) {
requestInterruption();
requestReady.release();
wait();
} else {
px_proxy_factory_free(factory);
}
}
/*
Gets the list of proxies from libproxy, converted to QUrl list.
Thread safe, according to libproxy documentation.
Gets the list of proxies from libproxy, converted to QUrl list. Apply
thread-safety, though its documentation says otherwise, libproxy isn't
thread-safe.
*/
QList<QUrl> QLibProxyWrapper::getProxies(const QUrl &url)
{
QList<QUrl> ret;
QByteArray encodedUrl = url.toEncoded();
Data data;
data.url = encodedUrl.constData();
if (factory) {
char **proxies = px_proxy_factory_get_proxies(factory, url.toEncoded());
if (proxies) {
for (int i = 0; proxies[i]; i++) {
ret.append(QUrl::fromEncoded(proxies[i]));
free(proxies[i]);
}
free(proxies);
{
QMutexLocker locker(&mutex);
if (isRunning()) {
// threaded mode
// it's safe to write to request because we hold the mutex:
// our aux thread is blocked waiting for work and no other thread
// could have got here
request = &data;
requestReady.release();
// wait for the reply
data.replyReady.acquire();
} else {
// non-threaded mode
data.proxies = px_proxy_factory_get_proxies(factory, data.url);
}
}
QList<QUrl> ret;
if (data.proxies) {
for (int i = 0; data.proxies[i]; i++) {
ret.append(QUrl::fromEncoded(data.proxies[i]));
free(data.proxies[i]);
}
free(data.proxies);
}
return ret;
}
void QLibProxyWrapper::run()
{
factory = px_proxy_factory_new();
Q_CHECK_PTR(factory);
forever {
requestReady.acquire();
if (isInterruptionRequested())
break;
request->proxies = px_proxy_factory_get_proxies(factory, request->url);
request->replyReady.release();
}
px_proxy_factory_free(factory);
}
QList<QNetworkProxy> QNetworkProxyFactory::systemProxyForQuery(const QNetworkProxyQuery &query)
{
QList<QNetworkProxy> proxyList;
@ -161,4 +254,6 @@ QList<QNetworkProxy> QNetworkProxyFactory::systemProxyForQuery(const QNetworkPro
QT_END_NAMESPACE
#include "qnetworkproxy_libproxy.moc"
#endif