Rollup merge of rust-lang#118169 - SparrowLii:deadlock_issue, r=compiler-errors

print query map for deadlock when using parallel front end

print query map for deadlock when using parallel front end, so that we can analyze where and why deadlock occurs

Author: matthiaskrgr

compiler/rustc_query_system/src/query/job.rs

@@ -38,7 +38,7 @@ pub struct QueryInfo {
 pub type QueryMap = FxHashMap<QueryJobId, QueryJobInfo>;
 
 /// A value uniquely identifying an active query job.
-#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
 pub struct QueryJobId(pub NonZeroU64);
 
 impl QueryJobId {
@@ -62,14 +62,14 @@ impl QueryJobId {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct QueryJobInfo {
     pub query: QueryStackFrame,
     pub job: QueryJob,
 }
 
 /// Represents an active query job.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct QueryJob {
     pub id: QueryJobId,
 
@@ -182,6 +182,7 @@ impl QueryJobId {
 }
 
 #[cfg(parallel_compiler)]
+#[derive(Debug)]
 struct QueryWaiter {
     query: Option<QueryJobId>,
     condvar: Condvar,
@@ -198,13 +199,14 @@ impl QueryWaiter {
 }
 
 #[cfg(parallel_compiler)]
+#[derive(Debug)]
 struct QueryLatchInfo {
     complete: bool,
     waiters: Vec<Arc<QueryWaiter>>,
 }
 
 #[cfg(parallel_compiler)]
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub(super) struct QueryLatch {
     info: Arc<Mutex<QueryLatchInfo>>,
 }
@@ -540,7 +542,11 @@ pub fn deadlock(query_map: QueryMap, registry: &rayon_core::Registry) {
     // X to Y due to Rayon waiting and a true dependency from Y to X. The algorithm here
     // only considers the true dependency and won't detect a cycle.
     if !found_cycle {
-        panic!("deadlock detected");
+        if query_map.len() == 0 {
+            panic!("deadlock detected without any query!")
+        } else {
+            panic!("deadlock detected! current query map:\n{:#?}", query_map);
+        }
     }
 
     // FIXME: Ensure this won't cause a deadlock before we return

compiler/rustc_query_system/src/query/plumbing.rs

@@ -203,7 +203,7 @@ where
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub(crate) struct CycleError {
     /// The query and related span that uses the cycle.
     pub usage: Option<(Span, QueryStackFrame)>,