D-Bus is not thread safe

...so it could happen that both the main thread at

> internal_bus_get
> dbus_bus_get_private
> avahi_dbus_bus_get
> avahi_client_new
> sd::AvahiNetworkService::setup
> sd::DiscoveryService::DiscoveryService
> sd::DiscoveryService::setup
> SdDLL::RegisterRemotes
[...]

as well as the thread

> internal_bus_get
> dbus_bus_get
> dbusConnectToNameOnBus
> sd::BluetoothServer::run
> threadFunc
> osl_thread_start_Impl
> start_thread

spawned from the main thread at

> sd::BluetoothServer::setup
> sd::RemoteServer::setup
> SdDLL::RegisterRemotes
[...]

are in D-Bus's internal_bus_get simultaneously (with disastrous consequences,
like SEGV) despite the _DBUS_LOCK(bus) there, unless you previously called
dbus_threads_init_default.  (Which the D-Bus documentation makes you believe can
be called from multiple threads, though a look at the implemenation makes it
clear that it really should be called from the main thread before any other
threads are created---which we still don't do; oh my.)

Other places that (indirectly) use D-Bus (tubes/source/file-transfer-helper.c,
vcl/generic/fontmanager/fontconfig.cxx, vcl/unx/gtk/window/gtksalframe.cxx might
need this, too.

Change-Id: I912829c615b46b05a89c07bd044b04f1e5f5e7ba

2 files changed, 18 insertions, 0 deletions

diff --git a/sd/source/ui/remotecontrol/AvahiNetworkService.cxx b/sd/source/ui/remotecontrol/AvahiNetworkService.cxx
index 8fc4eb7216bb..34b94a364c0e 100644
--- a/sd/source/ui/remotecontrol/AvahiNetworkService.cxx
+++ b/sd/source/ui/remotecontrol/AvahiNetworkService.cxx
@@ -8,6 +8,7 @@
  */
 #include <time.h>
 #include <iostream>
+#include <new>
 #include <stdlib.h>
 #include <assert.h>
 
@@ -20,6 +21,8 @@
 #include <avahi-common/timeval.h>
 #include <avahi-common/thread-watch.h>
 
+#include <dbus/dbus.h>
+
 #include <sal/log.hxx>
 
 #include "AvahiNetworkService.hxx"
@@ -149,6 +152,13 @@ static void client_callback(AvahiClient *c, AvahiClientState state, AVAHI_GCC_UN
 }
 
 void AvahiNetworkService::setup() {
+    // Avahi internally uses D-Bus, which requires the following in order to be
+    // thread-safe (and we potentially access D-Bus from different threads in
+    // different places of the code base):
+    if (!dbus_threads_init_default()) {
+        throw std::bad_alloc();
+    }
+
    int error = 0;
    avahiService = this;
    if (!(threaded_poll = avahi_threaded_poll_new())) {
diff --git a/sd/source/ui/remotecontrol/BluetoothServer.cxx b/sd/source/ui/remotecontrol/BluetoothServer.cxx
index ccdf03f31ac5..1deab3c6668b 100644
--- a/sd/source/ui/remotecontrol/BluetoothServer.cxx
+++ b/sd/source/ui/remotecontrol/BluetoothServer.cxx
@@ -11,6 +11,7 @@
 
 #include <iostream>
 #include <iomanip>
+#include <new>
 
 #include <sal/log.hxx>
 
@@ -586,6 +587,13 @@ BluetoothServer::BluetoothServer( std::vector<Communicator*>* pCommunicators )
     mpCommunicators( pCommunicators )
 {
 #ifdef LINUX_BLUETOOTH
+    // D-Bus requires the following in order to be thread-safe (and we
+    // potentially access D-Bus from different threads in different places of
+    // the code base):
+    if (!dbus_threads_init_default()) {
+        throw std::bad_alloc();
+    }
+
     mpImpl.reset(new BluetoothServer::Impl());
 #endif
 }