Fix a race condition

diff --git a/src/librustc/ty/query/job.rs b/src/librustc/ty/query/job.rs
index d5bf3856bc43256240ee5d4e3a3a2515d9714285..1439e41bb31fd9ba5924683d19947288f657be9a 100644 (file)
--- a/src/librustc/ty/query/job.rs
+++ b/src/librustc/ty/query/job.rs
@@ -103,8 +103,11 @@ pub(super) fn await<'lcx>(
                     condvar: Condvar::new(),
                 });
                 self.latch.await(&waiter);
-
-                match Lrc::get_mut(&mut waiter).unwrap().cycle.get_mut().take() {
+                // FIXME: Get rid of this lock. We have ownership of the QueryWaiter
+                // although another thread may still have a Lrc reference so we cannot
+                // use Lrc::get_mut
+                let mut cycle = waiter.cycle.lock();
+                match cycle.take() {
                     None => Ok(()),
                     Some(cycle) => Err(cycle)
                 }