Address comments

compiler/rustc_query_system/src/query/job.rs

@@ -588,7 +588,12 @@ pub fn print_query_stack<Qcx: QueryContext>(
     // state if it was responsible for triggering the panic.
     let mut count_printed = 0;
     let mut count_total = 0;
-    let query_map = qcx.collect_active_jobs().0;
+
+    // Make use of a partial query map if we fail to take locks collecting active queries.
+    let query_map = match qcx.collect_active_jobs() {
+        Ok(query_map) => query_map,
+        Err(query_map) => query_map,
+    };
 
     if let Some(ref mut file) = file {
         let _ = writeln!(file, "\n\nquery stack during panic:");

compiler/rustc_query_system/src/query/mod.rs

@@ -86,7 +86,7 @@ pub trait QueryContext: HasDepContext {
     /// Get the query information from the TLS context.
     fn current_query_job(self) -> Option<QueryJobId>;
 
-    fn collect_active_jobs(self) -> (QueryMap, bool);
+    fn collect_active_jobs(self) -> Result<QueryMap, QueryMap>;
 
     /// Load a side effect associated to the node in the previous session.
     fn load_side_effect(

compiler/rustc_query_system/src/query/plumbing.rs

@@ -250,10 +250,9 @@ where
     Q: QueryConfig<Qcx>,
     Qcx: QueryContext,
 {
-    let (query_map, complete) = qcx.collect_active_jobs();
     // Ensure there was no errors collecting all active jobs.
     // We need the complete map to ensure we find a cycle to break.
-    assert!(complete, "failed to collect active queries");
+    let query_map = qcx.collect_active_jobs().expect("failed to collect active queries");
 
     let error = try_execute.find_cycle_in_stack(query_map, &qcx.current_query_job(), span);
     (mk_cycle(query, qcx, error), None)