tunnel-sink-new: Fix hang when used in combination with module-combine-sink

When tunnel-sink-new was used in combination with module-combine-sink, PA
would hang because the main thread was blocked waiting for the execution
of the latency snapshot message. The message would never be processed
because the rtpoll associated with the control_inq of module-combine-sink
was never run.
This patch fixes the problem by running the rtpoll in the thread function
to process incoming messages. Though there are no users of the rtpoll for
module-tunnel-source-new, the same change is applied there.

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/773>

2 files changed, 24 insertions, 12 deletions

diff --git a/src/modules/module-tunnel-sink-new.c b/src/modules/module-tunnel-sink-new.c
index 3cea25a90..0b91ce266 100644
--- a/src/modules/module-tunnel-sink-new.c
+++ b/src/modules/module-tunnel-sink-new.c
@@ -253,9 +253,14 @@ static void thread_func(void *userdata) {
                     pa_log_error("Could not write data into the stream ... ret = %i", ret);
                     u->thread_mainloop_api->quit(u->thread_mainloop_api, TUNNEL_THREAD_FAILED_MAINLOOP);
                 }
-
             }
         }
+
+        /* Run the rtpoll to process messages that other modules (module-combine-sink,
+         * module-loopback and module-rtp-recv) may have placed in the queue. */
+        pa_rtpoll_set_timer_relative(u->rtpoll, 0);
+        if (pa_rtpoll_run(u->rtpoll) < 0)
+            goto fail;
     }
 fail:
     /* send a message to the ctl thread to ask it to either terminate us, or
@@ -696,13 +701,13 @@ static int do_init(pa_module *m) {
     u->msg = pa_msgobject_new(tunnel_msg);
     u->msg->parent.process_msg = tunnel_process_msg;
 
-    /* The rtpoll created here is never run. It is only necessary to avoid crashes
-     * when module-tunnel-sink-new is used together with module-loopback or
-     * module-combine-sink. Both modules base their asyncmsq on the rtpoll provided
-     * by the sink. module-loopback and combine-sink only work because they call
-     * pa_asyncmsq_process_one() themselves. module_rtp_recv also uses the rtpoll,
-     * but never calls pa_asyncmsq_process_one(), so it will not work in combination
-     * with module-tunnel-sink-new. */
+    /* The rtpoll created here is only run for the sake of module-combine-sink. It must
+     * exist to avoid crashes when module-tunnel-sink-new is used together with
+     * module-loopback or module-combine-sink. Both modules base their asyncmsgq on the
+     * rtpoll provided by the sink. module-loopback and combine-sink only work because
+     * they call pa_asyncmsq_process_one() themselves. module-combine-sink does this
+     * however only for the audio_inq, so without running the rtpoll, messages placed
+     * in control_inq would never be executed. */
     u->rtpoll = pa_rtpoll_new();
 
     default_sink_name = pa_sprintf_malloc("tunnel-sink-new.%s", remote_server);
diff --git a/src/modules/module-tunnel-source-new.c b/src/modules/module-tunnel-source-new.c
index b96137a24..d75fe9e6b 100644
--- a/src/modules/module-tunnel-source-new.c
+++ b/src/modules/module-tunnel-source-new.c
@@ -270,6 +270,11 @@ static void thread_func(void *userdata) {
 
         if (u->new_data)
             read_new_samples(u);
+
+        /* Run the rtpoll to process messages that other modules may have placed in the queue. */
+        pa_rtpoll_set_timer_relative(u->rtpoll, 0);
+        if (pa_rtpoll_run(u->rtpoll) < 0)
+            goto fail;
     }
 fail:
     /* send a message to the ctl thread to ask it to either terminate us, or
@@ -668,10 +673,12 @@ static int do_init(pa_module *m) {
     u->msg = pa_msgobject_new(tunnel_msg);
     u->msg->parent.process_msg = tunnel_process_msg;
 
-    /* The rtpoll created here is never run. It is only necessary to avoid crashes
-     * when module-tunnel-source-new is used together with module-loopback.
-     * module-loopback bases the asyncmsq on the rtpoll provided by the source and
-     * only works because it calls pa_asyncmsq_process_one(). */
+    /* The rtpoll created here must curently only exist to avoid crashes when
+     * the module is used together with module-loopback. Because module-loopback
+     * runs pa_asyncmsgq_process_one() from the pop callback, the rtpoll need not
+     * be run. We will do so anyway for potential modules similar to
+     * module-combine-sink that use the rtpoll of the underlying source for
+     * message exchange. */
     u->rtpoll = pa_rtpoll_new();
 
     default_source_name = pa_sprintf_malloc("tunnel-source-new.%s", remote_server);