[vlc-commits] upnp: fix deadlock when calling UpnpFinish locked

[Thomas Guillem]

vlc | branch: master | Thomas Guillem <thomas at gllm.fr> | Wed Feb  3 13:19:44 2016 +0100| [7e11257c2823417b582f4e4ad3108dce7c4c372e] | committer: Thomas Guillem

upnp: fix deadlock when calling UpnpFinish locked

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=7e11257c2823417b582f4e4ad3108dce7c4c372e
---

 modules/services_discovery/upnp.cpp |   16 +++++++++++++++-
 modules/services_discovery/upnp.hpp |    1 +
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/modules/services_discovery/upnp.cpp b/modules/services_discovery/upnp.cpp
index f7bfb4f..99988dd 100644
--- a/modules/services_discovery/upnp.cpp
+++ b/modules/services_discovery/upnp.cpp
@@ -73,6 +73,7 @@ struct access_sys_t
 
 UpnpInstanceWrapper* UpnpInstanceWrapper::s_instance;
 vlc_mutex_t UpnpInstanceWrapper::s_lock = VLC_STATIC_MUTEX;
+vlc_cond_t UpnpInstanceWrapper::s_cond = VLC_STATIC_COND;
 
 /*
  * VLC callback prototypes
@@ -1060,6 +1061,12 @@ UpnpInstanceWrapper::~UpnpInstanceWrapper()
 UpnpInstanceWrapper *UpnpInstanceWrapper::get(vlc_object_t *p_obj, Upnp_FunPtr callback, SD::MediaServerList *opaque)
 {
     vlc_mutex_locker lock( &s_lock );
+
+    /* refcount is 0 but instance is not NULL, UpnpFinish is being called so
+     * wait for it to finish */
+    while ( s_instance != NULL && s_instance->refcount_ == 0 )
+        vlc_cond_wait( &s_cond, &s_lock );
+
     if ( s_instance == NULL )
     {
         UpnpInstanceWrapper* instance = new(std::nothrow) UpnpInstanceWrapper;
@@ -1118,7 +1125,7 @@ UpnpInstanceWrapper *UpnpInstanceWrapper::get(vlc_object_t *p_obj, Upnp_FunPtr c
 
 void UpnpInstanceWrapper::release(bool isSd)
 {
-    vlc_mutex_locker lock( &s_lock );
+    vlc_mutex_lock( &s_lock );
     if ( isSd )
     {
         callback_ = NULL;
@@ -1126,9 +1133,16 @@ void UpnpInstanceWrapper::release(bool isSd)
     }
     if (--s_instance->refcount_ == 0)
     {
+        vlc_mutex_unlock( &s_lock );
+        /* UpnpFinish must be called unlocked since callbacks can still be
+         * called when shuting down upnp threads */
         delete s_instance;
+        vlc_mutex_lock( &s_lock );
+
         s_instance = NULL;
+        vlc_cond_signal( &s_cond );
     }
+    vlc_mutex_unlock( &s_lock );
 }
 
 UpnpClient_Handle UpnpInstanceWrapper::handle() const
diff --git a/modules/services_discovery/upnp.hpp b/modules/services_discovery/upnp.hpp
index 0cdbd8d..a6d720f 100644
--- a/modules/services_discovery/upnp.hpp
+++ b/modules/services_discovery/upnp.hpp
@@ -71,6 +71,7 @@ private:
 private:
     static UpnpInstanceWrapper* s_instance;
     static vlc_mutex_t s_lock;
+    static vlc_cond_t s_cond;
     UpnpClient_Handle handle_;
     SD::MediaServerList* opaque_;
     Upnp_FunPtr callback_;