Handle GET_PARAMETER keepalive responses during PAUSE

Fixes ticket#14939

Because Demux() is not called during PAUSE the GET_PARAMETER keepalives are
sent by the TimeoutPrevention thread.  However this was not giving Live555
a chance to handle the responses through doEventLoop(), and so the responses
were queued up.  Because of a separate issue in handling pipelined
GET_PARAMETER responses in Live555 itself (now fixed, 2015-06-24), after two
GPs this would result in the loss of the PLAY response on resume, locking
everything up.

Even with the fix to Live555, queuing up all GP responses until the stream
is resumed is unpleasant and will eventually overflow Live555's response
buffer.

This fix calls the usual Live555 response handling mechanism for GPs sent
in the background thread during pause.  I have not added it to the normal
GP sends in Demux() because that calls doEventLoop() anyway, and to do so
would add a delay to normal processing.

TimeoutPrevention now requires access to p_demux itself, not just p_sys.

A mutex has been added to protect LIVE555 from simultaneous calls within
Demux() or Control() and the TimeoutPrevention() thread
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/access/live555.cpp

@@ -173,7 +173,7 @@ typedef struct
 
 struct timeout_thread_t
 {
-    demux_sys_t  *p_sys;
+    demux_t     *p_demux;
     vlc_thread_t handle;
     bool         b_handle_keep_alive;
 };
@@ -210,6 +210,7 @@ struct demux_sys_t
     int              i_timeout;     /* session timeout value in seconds */
     bool             b_timeout_call;/* mark to send an RTSP call to prevent server timeout */
     timeout_thread_t *p_timeout;    /* the actual thread that makes sure we don't timeout */
+    vlc_mutex_t      timeout_mutex; /* Serialise calls to live555 in timeout thread w.r.t. Demux()/Control() */
 
     /* */
     bool             b_force_mcast;
@@ -310,6 +311,7 @@ static int  Open ( vlc_object_t *p_this )
     p_sys->psz_path = strdup( p_demux->psz_location );
     p_sys->b_force_mcast = var_InheritBool( p_demux, "rtsp-mcast" );
     p_sys->f_seek_request = -1;
+    vlc_mutex_init(&p_sys->timeout_mutex);
 
     /* parse URL for rtsp://[user:[passwd]@]serverip:port/options */
     vlc_UrlParse( &p_sys->url, p_sys->psz_path, 0 );
@@ -456,6 +458,7 @@ static void Close( vlc_object_t *p_this )
     free( p_sys->psz_path );
 
     vlc_UrlClean( &p_sys->url );
+    vlc_mutex_destroy(&p_sys->timeout_mutex);
 
     free( p_sys );
 }
@@ -1238,7 +1241,7 @@ static int Play( demux_t *p_demux )
             if( p_sys->p_timeout )
             {
                 memset( p_sys->p_timeout, 0, sizeof(timeout_thread_t) );
-                p_sys->p_timeout->p_sys = p_demux->p_sys; /* lol, object recursion :D */
+                p_sys->p_timeout->p_demux = p_demux;
                 if( vlc_clone( &p_sys->p_timeout->handle,  TimeoutPrevention,
                                p_sys->p_timeout, VLC_THREAD_PRIORITY_LOW ) )
                 {
@@ -1276,6 +1279,10 @@ static int Demux( demux_t *p_demux )
     bool            b_send_pcr = true;
     int             i;
 
+    /* Protect Live555 from simultaneous calls in TimeoutPrevention()
+       during pause */
+    vlc_mutex_locker locker(&p_sys->timeout_mutex);
+
     /* Check if we need to send the server a Keep-A-Live signal */
     if( p_sys->b_timeout_call && p_sys->rtsp && p_sys->ms )
     {
@@ -1431,6 +1438,8 @@ static int Control( demux_t *p_demux, int i_query, va_list args )
     bool *pb, *pb2;
     int *pi_int;
 
+    vlc_mutex_locker locker(&p_sys->timeout_mutex); /* (see same in Demux) */
+
     switch( i_query )
     {
         case DEMUX_GET_TIME:
@@ -2111,21 +2120,35 @@ VLC_NORETURN
 static void* TimeoutPrevention( void *p_data )
 {
     timeout_thread_t *p_timeout = (timeout_thread_t *)p_data;
+    demux_t *p_demux = p_timeout->p_demux;
+    demux_sys_t *p_sys = p_demux->p_sys;
 
     for( ;; )
     {
         /* Voodoo (= no) thread safety here! *Ahem* */
         if( p_timeout->b_handle_keep_alive )
         {
+            /* Protect Live555 from us calling their functions simultaneously
+               with Demux() or Control() */
+            vlc_mutex_locker locker(&p_sys->timeout_mutex);
+
             char *psz_bye = NULL;
             int canc = vlc_savecancel ();
 
-            p_timeout->p_sys->rtsp->sendGetParameterCommand( *p_timeout->p_sys->ms, NULL, psz_bye );
+            p_sys->rtsp->sendGetParameterCommand( *p_sys->ms, default_live555_callback, psz_bye );
+
+            if( !wait_Live555_response( p_demux ) )
+            {
+              msg_Err( p_demux, "GET_PARAMETER keepalive failed: %s",
+                       p_sys->env->getResultMsg() );
+              /* Just continue, worst case is we get timed out later */
+            }
+
             vlc_restorecancel (canc);
         }
-        p_timeout->p_sys->b_timeout_call = !p_timeout->b_handle_keep_alive;
+        p_sys->b_timeout_call = !p_timeout->b_handle_keep_alive;
 
-        msleep (((int64_t)p_timeout->p_sys->i_timeout - 2) * CLOCK_FREQ);
+        msleep (((int64_t)p_sys->i_timeout - 2) * CLOCK_FREQ);
     }
     vlc_assert_unreachable(); /* dead code */
 }