uridecodebin: stop using crossbeam_channel

I give up on crossbeam_channel. For some reasons some receivers are not
always unblocked and I was not able to reproduce using simpler test
cases.
Use with mpsc channels instead which are more reliable.

Cargo.lock

@@ -1781,7 +1781,6 @@ name = "gst-plugin-uriplaylistbin"
 version = "0.8.3"
 dependencies = [
  "anyhow",
- "crossbeam-channel",
  "gst-plugin-version-helper",
  "gstreamer",
  "gstreamer-app",

utils/uriplaylistbin/Cargo.toml

@@ -11,7 +11,6 @@ description = "Playlist Plugin"
 gst = { package = "gstreamer", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", branch = "0.18", version = "0.18", features = ["v1_14"] }
 once_cell = "1.0"
 anyhow = "1"
-crossbeam-channel = "0.5"
 
 [dev-dependencies]
 gst-app = { package = "gstreamer-app", git = "https://gitlab.freedesktop.org/gstreamer/gstreamer-rs", branch = "0.18", version = "0.18",  features = ["v1_14"]}

utils/uriplaylistbin/src/uriplaylistbin/imp.rs

@@ -7,7 +7,7 @@
 // SPDX-License-Identifier: MPL-2.0
 
 use std::sync::Arc;
-use std::sync::{Mutex, MutexGuard};
+use std::sync::{mpsc, Mutex, MutexGuard};
 
 use gst::glib;
 use gst::prelude::*;
@@ -175,7 +175,7 @@ impl State {
 
     fn unblock_item(&mut self, element: &super::UriPlaylistBin) {
         if let Some(blocked) = self.blocked.take() {
-            let (messages, sender) = blocked.set_streaming(self.streams_topology.n_streams());
+            let (messages, channels) = blocked.set_streaming(self.streams_topology.n_streams());
 
             gst_log!(
                 CAT,
@@ -188,7 +188,8 @@ impl State {
             for msg in messages {
                 let _ = element.post_message(msg);
             }
-            let _ = sender.send(true);
+
+            channels.send(true);
 
             self.streaming.push(blocked);
         }
@@ -218,9 +219,8 @@ enum ItemState {
         /// number of streamsynchronizer src pads which are not eos yet
         waiting_eos: u32,
         stream_collection_msg: gst::Message,
-        // channel used to block pads flow until streamsynchronizer is eos
+        // channels used to block pads flow until streamsynchronizer is eos
-        sender: crossbeam_channel::Sender<bool>,
+        channels: Channels,
-        receiver: crossbeam_channel::Receiver<bool>,
     },
     /// Waiting that pads of all the streams have been created on decodebin.
     /// Required to ensure that streams are plugged to concat in the playlist order.
@@ -230,9 +230,8 @@ enum ItemState {
         stream_collection_msg: gst::Message,
         /// concat sink pads which have been requested to handle this item
         concat_sink_pads: Vec<(gst::Element, gst::Pad)>,
-        // channel used to block pad flow in the Blocked state
+        // channels used to block pad flow in the Blocked state
-        sender: crossbeam_channel::Sender<bool>,
+        channels: Channels,
-        receiver: crossbeam_channel::Receiver<bool>,
     },
     /// Pads have been linked to `concat` elements but are blocked until the next item is linked to `concat` as well.
     /// This is required to ensure gap-less transition between items.
@@ -241,7 +240,7 @@ enum ItemState {
         stream_collection_msg: gst::Message,
         stream_selected_msg: Option<gst::Message>,
         concat_sink_pads: Vec<(gst::Element, gst::Pad)>,
-        sender: crossbeam_channel::Sender<bool>,
+        channels: Channels,
     },
     /// Buffers are flowing
     Streaming {
@@ -333,15 +332,17 @@ impl Item {
         }
     }
 
-    fn receiver(&self) -> crossbeam_channel::Receiver<bool> {
+    fn receiver(&self) -> mpsc::Receiver<bool> {
-        let inner = self.inner.lock().unwrap();
+        let mut inner = self.inner.lock().unwrap();
 
-        match &inner.state {
+        let channels = match &mut inner.state {
-            ItemState::WaitingForPads { receiver, .. } => receiver.clone(),
+            ItemState::WaitingForPads { channels, .. } => channels,
-            ItemState::WaitingForStreamsynchronizerEos { receiver, .. } => receiver.clone(),
+            ItemState::WaitingForStreamsynchronizerEos { channels, .. } => channels,
             // receiver is no longer supposed to be accessed once in the `Blocked` state
             _ => panic!("invalid state: {:?}", inner.state),
-        }
+        };
+
+        channels.get_receiver()
     }
 
     fn add_blocked_pad(&self, pad: gst::Pad) {
@@ -443,8 +444,6 @@ impl Item {
             ItemState::WaitingForStreamCollection { .. }
         ));
 
-        let (sender, receiver) = crossbeam_channel::unbounded::<bool>();
-
         match &inner.state {
             ItemState::WaitingForStreamCollection { uridecodebin } => {
                 inner.state = ItemState::WaitingForPads {
@@ -452,8 +451,7 @@ impl Item {
                     n_pads_pendings: n_streams,
                     stream_collection_msg: msg.copy(),
                     concat_sink_pads: vec![],
-                    sender,
+                    channels: Channels::default(),
-                    receiver,
                 };
             }
             _ => panic!("invalid state: {:?}", inner.state),
@@ -465,7 +463,6 @@ impl Item {
     // having to wait until streamsynchronizer is flushed to internally reorganize the element.
     fn set_waiting_for_ss_eos(&self, waiting_eos: u32, msg: gst::message::StreamCollection) {
         let mut inner = self.inner.lock().unwrap();
-        let (sender, receiver) = crossbeam_channel::unbounded::<bool>();
 
         match &inner.state {
             ItemState::WaitingForStreamCollection { uridecodebin } => {
@@ -475,8 +472,7 @@ impl Item {
                     waiting_eos,
                     // FIXME: save deep copy once https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/-/issues/363 is fixed
                     stream_collection_msg: msg.copy(),
-                    sender,
+                    channels: Channels::default(),
-                    receiver,
                 };
             }
             _ => panic!("invalid state: {:?}", inner.state),
@@ -485,13 +481,7 @@ impl Item {
 
     // from the WaitingForStreamsynchronizerEos state, called when the streamsynchronizer has been flushed
     // and the item can now be processed.
-    fn done_waiting_for_ss_eos(
+    fn done_waiting_for_ss_eos(&self) -> (StreamsTopology, Vec<gst::Pad>, Channels) {
-        &self,
-    ) -> (
-        StreamsTopology,
-        Vec<gst::Pad>,
-        crossbeam_channel::Sender<bool>,
-    ) {
         let mut inner = self.inner.lock().unwrap();
 
         match &inner.state {
@@ -500,7 +490,7 @@ impl Item {
                 decodebin_pads,
                 waiting_eos,
                 stream_collection_msg,
-                sender,
+                channels,
                 ..
             } => {
                 assert_eq!(*waiting_eos, 0);
@@ -512,20 +502,17 @@ impl Item {
                     _ => unreachable!(),
                 };
                 let pending_pads = decodebin_pads.clone();
-                let sender = sender.clone();
+                let channels = channels.clone();
-
-                let (new_sender, new_receiver) = crossbeam_channel::unbounded::<bool>();
 
                 inner.state = ItemState::WaitingForPads {
                     uridecodebin: uridecodebin.clone(),
                     n_pads_pendings: topology.n_streams(),
                     stream_collection_msg: stream_collection_msg.copy(),
                     concat_sink_pads: vec![],
-                    sender: new_sender,
+                    channels: Channels::default(),
-                    receiver: new_receiver,
                 };
 
-                (topology, pending_pads, sender)
+                (topology, pending_pads, channels)
             }
             _ => panic!("invalid state: {:?}", inner.state),
         }
@@ -538,14 +525,14 @@ impl Item {
         match &mut inner.state {
             ItemState::WaitingForPads {
                 uridecodebin,
-                sender,
+                channels,
                 stream_collection_msg,
                 concat_sink_pads,
                 ..
             } => {
                 inner.state = ItemState::Blocked {
                     uridecodebin: uridecodebin.clone(),
-                    sender: sender.clone(),
+                    channels: channels.clone(),
                     concat_sink_pads: concat_sink_pads.clone(),
                     stream_collection_msg: stream_collection_msg.copy(),
                     stream_selected_msg: None,
@@ -557,16 +544,13 @@ impl Item {
 
     // from the Blocked state, called when the item streaming threads can be unblocked.
     // Return the queued messages from this item and the sender to unblock their pads
-    fn set_streaming(
+    fn set_streaming(&self, n_streams: u32) -> (Vec<gst::Message>, Channels) {
-        &self,
-        n_streams: u32,
-    ) -> (Vec<gst::Message>, crossbeam_channel::Sender<bool>) {
         let mut inner = self.inner.lock().unwrap();
 
         match &mut inner.state {
             ItemState::Blocked {
                 uridecodebin,
-                sender,
+                channels,
                 stream_collection_msg,
                 stream_selected_msg,
                 concat_sink_pads,
@@ -576,7 +560,7 @@ impl Item {
                 if let Some(msg) = stream_selected_msg {
                     messages.push(msg.copy());
                 }
-                let sender = sender.clone();
+                let channels = channels.clone();
 
                 inner.state = ItemState::Streaming {
                     uridecodebin: uridecodebin.clone(),
@@ -584,7 +568,7 @@ impl Item {
                     concat_sink_pads: concat_sink_pads.clone(),
                 };
 
-                (messages, sender)
+                (messages, channels)
             }
             _ => panic!("invalid state: {:?}", inner.state),
         }
@@ -609,13 +593,13 @@ impl Item {
         }
     }
 
-    fn sender(&self) -> crossbeam_channel::Sender<bool> {
+    fn channels(&self) -> Channels {
         let inner = self.inner.lock().unwrap();
 
         match &inner.state {
-            ItemState::WaitingForStreamsynchronizerEos { sender, .. } => sender.clone(),
+            ItemState::WaitingForStreamsynchronizerEos { channels, .. } => channels.clone(),
-            ItemState::WaitingForPads { sender, .. } => sender.clone(),
+            ItemState::WaitingForPads { channels, .. } => channels.clone(),
-            ItemState::Blocked { sender, .. } => sender.clone(),
+            ItemState::Blocked { channels, .. } => channels.clone(),
             _ => panic!("invalid state: {:?}", inner.state),
         }
     }
@@ -955,13 +939,13 @@ impl ElementImpl for UriPlaylistBin {
             // As a result we have to explicitly unblock all receivers as dropping the sender
             // is not enough.
             if let Some(item) = state.waiting_for_ss_eos.take() {
-                let _ = item.sender().send(false);
+                item.channels().send(false);
             }
             if let Some(item) = state.waiting_for_pads.take() {
-                let _ = item.sender().send(false);
+                item.channels().send(false);
             }
             if let Some(item) = state.blocked.take() {
-                let _ = item.sender().send(false);
+                item.channels().send(false);
             }
         }
 
@@ -1086,7 +1070,7 @@ impl UriPlaylistBin {
             if let Some(item) = state.waiting_for_ss_eos.as_ref() {
                 // block pad until streamsynchronizer is eos
                 let element_weak = element.downgrade();
-                let receiver = item.receiver();
+                let receiver = Mutex::new(item.receiver());
 
                 gst_debug!(
                     CAT,
@@ -1102,6 +1086,7 @@ impl UriPlaylistBin {
                     };
                     let parent = pad.parent().unwrap();
 
+                    let receiver = receiver.lock().unwrap();
                     let _ = receiver.recv();
 
                     gst_log!(
@@ -1409,7 +1394,7 @@ impl UriPlaylistBin {
             item.add_concat_sink_pad(&concat, &sink_pad);
 
             // block pad until next item is reaching the `Blocked` state
-            let receiver = item.receiver();
+            let receiver = Mutex::new(item.receiver());
             let element_weak = element.downgrade();
             let item_clone = item.clone();
 
@@ -1431,6 +1416,8 @@ impl UriPlaylistBin {
                         pad.name()
                     );
 
+                    let receiver = receiver.lock().unwrap();
+
                     if let Ok(false) = receiver.recv() {
                         // we are shutting down so remove the probe.
                         // Don't handle Err(_) here as if the item has multiple pads, the sender may be dropped in unblock_item()
@@ -1534,7 +1521,7 @@ impl UriPlaylistBin {
     /// and so the elements can reorganize itself to handle a pending changes in
     /// streams topology.
     fn handle_topology_change(&self, element: &super::UriPlaylistBin) {
-        let (pending_pads, sender) = {
+        let (pending_pads, channels) = {
             let mut state_guard = self.state.lock().unwrap();
             let state = state_guard.as_mut().unwrap();
 
@@ -1543,7 +1530,7 @@ impl UriPlaylistBin {
                 None => return, // element is being shutdown
             };
 
-            let (topology, pending_pads, sender) = item.done_waiting_for_ss_eos();
+            let (topology, pending_pads, channels) = item.done_waiting_for_ss_eos();
             state.waiting_for_pads = Some(item);
 
             // remove now useless concat elements, missing ones will be added when handling src pads from decodebin
@@ -1603,7 +1590,7 @@ impl UriPlaylistBin {
 
             state.streams_topology = topology;
 
-            (pending_pads, sender)
+            (pending_pads, channels)
         };
 
         // process decodebin src pads we already received and unblock them
@@ -1611,7 +1598,7 @@ impl UriPlaylistBin {
             self.process_decodebin_pad(pad);
         }
 
-        let _ = sender.send(true);
+        channels.send(true);
     }
 
     fn failed(&self, element: &super::UriPlaylistBin, error: PlaylistError) {
@@ -1692,3 +1679,25 @@ impl UriPlaylistBin {
         }
     }
 }
+
+#[derive(Default, Clone, Debug)]
+struct Channels {
+    senders: Arc<Mutex<Vec<mpsc::Sender<bool>>>>,
+}
+
+impl Channels {
+    fn get_receiver(&self) -> mpsc::Receiver<bool> {
+        let mut senders = self.senders.lock().unwrap();
+
+        let (sender, receiver) = mpsc::channel();
+        senders.push(sender);
+        receiver
+    }
+
+    fn send(&self, val: bool) {
+        let mut senders = self.senders.lock().unwrap();
+
+        // remove sender if sending failed
+        senders.retain(|sender| sender.send(val).is_ok());
+    }
+}