demux: replace demux_pause/demux_unpause with demux_run_on_thread

This pause stuff is bothersome and is needed only for a few corner-
cases. This commit removes it from the demuxer public API and replaces
it with a demux_run_on_thread() function and refactors the code which
needed demux_pause(). The next commit will change the implementation.

demux/demux.c

@@ -1533,20 +1533,22 @@ static int cached_demux_control(struct demux_internal *in, int cmd, void *arg)
     return DEMUXER_CTRL_DONTKNOW;
 }
 
-int demux_control(demuxer_t *demuxer, int cmd, void *arg)
+struct demux_control_args {
+    struct demuxer *demuxer;
+    int cmd;
+    void *arg;
+    int *r;
+};
+
+static void thread_demux_control(void *p)
 {
+    struct demux_control_args *args = p;
+    struct demuxer *demuxer = args->demuxer;
+    int cmd = args->cmd;
+    void *arg = args->arg;
     struct demux_internal *in = demuxer->in;
-
-    if (in->threading) {
-        pthread_mutex_lock(&in->lock);
-        int cr = cached_demux_control(in, cmd, arg);
-        pthread_mutex_unlock(&in->lock);
-        if (cr != DEMUXER_CTRL_DONTKNOW)
-            return cr;
-    }
-
     int r = DEMUXER_CTRL_NOTIMPL;
-    demux_pause(demuxer);
+
     if (cmd == DEMUXER_CTRL_STREAM_CTRL) {
         struct demux_ctrl_stream_ctrl *c = arg;
         if (in->threading)
@@ -1561,7 +1563,26 @@ int demux_control(demuxer_t *demuxer, int cmd, void *arg)
         if (demuxer->desc->control)
             r = demuxer->desc->control(demuxer->in->d_thread, cmd, arg);
     }
-    demux_unpause(demuxer);
+
+    *args->r = r;
+}
+
+int demux_control(demuxer_t *demuxer, int cmd, void *arg)
+{
+    struct demux_internal *in = demuxer->in;
+
+    if (in->threading) {
+        pthread_mutex_lock(&in->lock);
+        int cr = cached_demux_control(in, cmd, arg);
+        pthread_mutex_unlock(&in->lock);
+        if (cr != DEMUXER_CTRL_DONTKNOW)
+            return cr;
+    }
+
+    int r = 0;
+    struct demux_control_args args = {demuxer, cmd, arg, &r};
+    demux_run_on_thread(demuxer, thread_demux_control, &args);
+
     return r;
 }
 
@@ -1575,7 +1596,7 @@ int demux_stream_control(demuxer_t *demuxer, int ctrl, void *arg)
 // Make the demuxer thread stop doing anything.
 // demux_unpause() wakes up the thread again.
 // Can be nested with other calls, but trying to read packets may deadlock.
-void demux_pause(demuxer_t *demuxer)
+static void demux_pause(demuxer_t *demuxer)
 {
     struct demux_internal *in = demuxer->in;
     assert(demuxer == in->d_user);
@@ -1593,7 +1614,7 @@ void demux_pause(demuxer_t *demuxer)
     pthread_mutex_unlock(&in->lock);
 }
 
-void demux_unpause(demuxer_t *demuxer)
+static void demux_unpause(demuxer_t *demuxer)
 {
     struct demux_internal *in = demuxer->in;
     assert(demuxer == in->d_user);
@@ -1608,6 +1629,13 @@ void demux_unpause(demuxer_t *demuxer)
     pthread_mutex_unlock(&in->lock);
 }
 
+void demux_run_on_thread(struct demuxer *demuxer, void (*fn)(void *), void *ctx)
+{
+    demux_pause(demuxer);
+    fn(ctx);
+    demux_unpause(demuxer);
+}
+
 bool demux_cancel_test(struct demuxer *demuxer)
 {
     return mp_cancel_test(demuxer->stream->cancel);

demux/demux.h

@@ -285,8 +285,7 @@ double demuxer_get_time_length(struct demuxer *demuxer);
 
 int demux_stream_control(demuxer_t *demuxer, int ctrl, void *arg);
 
-void demux_pause(demuxer_t *demuxer);
+void demux_run_on_thread(struct demuxer *demuxer, void (*fn)(void *), void *ctx);
-void demux_unpause(demuxer_t *demuxer);
 
 void demux_changed(demuxer_t *demuxer, int events);
 void demux_update(demuxer_t *demuxer);

player/command.c

@@ -419,6 +419,17 @@ static int mp_property_stream_path(void *ctx, struct m_property *prop,
     return m_property_strdup_ro(action, arg, stream->url);
 }
 
+struct change_stream_capture_args {
+    char *filename;
+    struct demuxer *demux;
+};
+
+static void do_change_stream_capture(void *p)
+{
+    struct change_stream_capture_args *args = p;
+    stream_set_capture_file(args->demux->stream, args->filename);
+}
+
 static int mp_property_stream_capture(void *ctx, struct m_property *prop,
                                       int action, void *arg)
 {
@@ -427,10 +438,8 @@ static int mp_property_stream_capture(void *ctx, struct m_property *prop,
         return M_PROPERTY_UNAVAILABLE;
 
     if (action == M_PROPERTY_SET) {
-        char *filename = *(char **)arg;
+        struct change_stream_capture_args args = {*(char **)arg, mpctx->demuxer};
-        demux_pause(mpctx->demuxer);
+        demux_run_on_thread(mpctx->demuxer, do_change_stream_capture, &args);
-        stream_set_capture_file(mpctx->demuxer->stream, filename);
-        demux_unpause(mpctx->demuxer);
         // fall through to mp_property_generic_option
     }
     return mp_property_generic_option(mpctx, prop, action, arg);
@@ -1077,11 +1086,12 @@ static int mp_property_angle(void *ctx, struct m_property *prop,
         if (angle < 0 || angle > angles)
             return M_PROPERTY_ERROR;
 
-        demux_pause(demuxer);
         demux_flush(demuxer);
         ris = demux_stream_control(demuxer, STREAM_CTRL_SET_ANGLE, &angle);
+        if (ris == STREAM_OK) {
             demux_control(demuxer, DEMUXER_CTRL_RESYNC, NULL);
-        demux_unpause(demuxer);
+            demux_flush(demuxer);
+        }
 
         reset_audio_state(mpctx);
         reset_video_state(mpctx);