Rollup merge of rust-lang#129271 - futile:query-system/prevent-double-panic, r=michaelwoerister

Prevent double panic in query system, improve diagnostics

I stumbled upon a double-panic in the query system while working on something else (rust-lang#129102), which hid the real error cause for what I was debugging. This PR remedies that, so unwinding should be able to present more errors. It shouldn't really be relevant for code that doesn't ICE.

Author: matthiaskrgr

compiler/rustc_query_impl/src/plumbing.rs

@@ -702,11 +702,17 @@ macro_rules! define_queries {
                     let name = stringify!($name);
                     $crate::plumbing::create_query_frame(tcx, rustc_middle::query::descs::$name, key, kind, name)
                 };
-                tcx.query_system.states.$name.try_collect_active_jobs(
+                let res = tcx.query_system.states.$name.try_collect_active_jobs(
                     tcx,
                     make_query,
                     qmap,
-                ).unwrap();
+                );
+                // this can be called during unwinding, and the function has a `try_`-prefix, so
+                // don't `unwrap()` here, just manually check for `None` and do best-effort error
+                // reporting.
+                if res.is_none() {
+                    tracing::warn!("Failed to collect active jobs for query with name `{}`!", stringify!($name));
+                }
             }
 
             pub fn alloc_self_profile_query_strings<'tcx>(tcx: TyCtxt<'tcx>, string_cache: &mut QueryKeyStringCache) {

compiler/rustc_query_system/src/query/plumbing.rs

@@ -181,8 +181,15 @@ where
         cache.complete(key, result, dep_node_index);
 
         let job = {
-            let mut lock = state.active.lock_shard_by_value(&key);
-            lock.remove(&key).unwrap().expect_job()
+            let val = {
+                // don't keep the lock during the `unwrap()` of the retrieved value, or we taint the
+                // underlying shard.
+                // since unwinding also wants to look at this map, this can also prevent a double
+                // panic.
+                let mut lock = state.active.lock_shard_by_value(&key);
+                lock.remove(&key)
+            };
+            val.unwrap().expect_job()
         };
 
         job.signal_complete();