Auto merge of #11585 - asajeffrey:constellation-avoid-deadlock-during-pipeline-closure, r=larsbergstrom

Avoid deadlock when closing a pipeline.

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At the moment, the constellation blocks on a pipeline during closure. This PR makes pipeline closure asynchronous.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #11546.
- [X] These changes do not require tests because testing for absence of deadlock is difficult.

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1 files changed, 4 insertions, 7 deletions

diff --git a/components/constellation/pipeline.rs b/components/constellation/pipeline.rs
index 3f4abbbbc3e..7718eb76036 100644
--- a/components/constellation/pipeline.rs
+++ b/components/constellation/pipeline.rs
@@ -309,6 +309,8 @@ impl Pipeline {
         // The compositor wants to know when pipelines shut down too.
         // It may still have messages to process from these other threads
         // before they can be safely shut down.
+        // It's OK for the constellation to block on the compositor,
+        // since the compositor never blocks on the constellation.
         if let Ok((sender, receiver)) = ipc::channel() {
             self.compositor_proxy.send(CompositorMsg::PipelineExited(self.id, sender));
             if let Err(e) = receiver.recv() {
@@ -318,13 +320,8 @@ impl Pipeline {
 
         // Script thread handles shutting down layout, and layout handles shutting down the painter.
         // For now, if the script thread has failed, we give up on clean shutdown.
-        if self.script_chan
-               .send(ConstellationControlMsg::ExitPipeline(self.id))
-               .is_ok() {
-            // Wait until all slave threads have terminated and run destructors
-            // NOTE: We don't wait for script thread as we don't always own it
-            let _ = self.paint_shutdown_port.recv();
-            let _ = self.layout_shutdown_port.recv();
+        if let Err(e) = self.script_chan.send(ConstellationControlMsg::ExitPipeline(self.id)) {
+            warn!("Sending script exit message failed ({}).", e);
         }
     }