Ensure that only one cache priming task can run at a time

Fixes #8632.

Author: Bobo1239

crates/rust-analyzer/src/global_state.rs

@@ -84,6 +84,7 @@ pub(crate) struct GlobalState {
     pub(crate) workspace_build_data: Option<BuildDataResult>,
     pub(crate) fetch_build_data_queue:
         OpQueue<BuildDataCollector, Option<anyhow::Result<BuildDataResult>>>,
+    pub(crate) prime_caches_queue: OpQueue<(), ()>,
 
     latest_requests: Arc<RwLock<LatestRequests>>,
 }
@@ -146,6 +147,7 @@ impl GlobalState {
             workspaces: Arc::new(Vec::new()),
             fetch_workspaces_queue: OpQueue::default(),
             workspace_build_data: None,
+            prime_caches_queue: OpQueue::default(),
 
             fetch_build_data_queue: OpQueue::default(),
             latest_requests: Default::default(),

crates/rust-analyzer/src/main_loop.rs

@@ -278,6 +278,8 @@ impl GlobalState {
                     };
                 }
 
+                let mut finished = false;
+
                 for progress in prime_caches_progress {
                     let (state, message, fraction);
                     match progress {
@@ -295,11 +297,18 @@ impl GlobalState {
                             state = Progress::End;
                             message = None;
                             fraction = 1.0;
+                            finished = true;
                         }
                     };
 
                     self.report_progress("Indexing", state, message, Some(fraction));
                 }
+
+                // If the task is cancelled we may observe two `PrimeCachesProgress::Finished` so we
+                // have to make sure to only call `op_completed()` once.
+                if finished {
+                    self.prime_caches_queue.op_completed(());
+                }
             }
             Event::Vfs(mut task) => {
                 let _p = profile::span("GlobalState::handle_event/vfs");
@@ -711,6 +720,13 @@ impl GlobalState {
     }
     fn update_file_notifications_on_threadpool(&mut self) {
         self.maybe_update_diagnostics();
+
+        // Ensure that only one cache priming task can run at a time
+        self.prime_caches_queue.request_op(());
+        if self.prime_caches_queue.should_start_op().is_none() {
+            return;
+        }
+
         self.task_pool.handle.spawn_with_sender({
             let snap = self.snapshot();
             move |sender| {