From 77259af56ab337d476cafeeb657c9b8953f8b75b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20K=C3=A5re=20Alsaker?= <john.kare.alsaker@gmail.com>
Date: Sun, 27 May 2018 07:46:19 +0200
Subject: [PATCH] Use try_lock in collect_active_jobs

---
 src/librustc/ty/maps/plumbing.rs     |  4 +++-
 src/librustc_data_structures/sync.rs | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/librustc/ty/maps/plumbing.rs b/src/librustc/ty/maps/plumbing.rs
index 2ab8d18e3e7d..13d2a13e5ddc 100644
--- a/src/librustc/ty/maps/plumbing.rs
+++ b/src/librustc/ty/maps/plumbing.rs
@@ -659,7 +659,9 @@ macro_rules! define_maps {
             pub fn collect_active_jobs(&self) -> Vec<Lrc<QueryJob<$tcx>>> {
                 let mut jobs = Vec::new();
 
-                $(for v in self.$name.lock().active.values() {
+                // We use try_lock here since we are only called from the
+                // deadlock handler, and this shouldn't be locked
+                $(for v in self.$name.try_lock().unwrap().active.values() {
                     match *v {
                         QueryResult::Started(ref job) => jobs.push(job.clone()),
                         _ => (),
diff --git a/src/librustc_data_structures/sync.rs b/src/librustc_data_structures/sync.rs
index 6f7d9e1b54b1..33f6eda2a875 100644
--- a/src/librustc_data_structures/sync.rs
+++ b/src/librustc_data_structures/sync.rs
@@ -519,6 +519,18 @@ impl<T> Lock<T> {
         self.0.get_mut()
     }
 
+    #[cfg(parallel_queries)]
+    #[inline(always)]
+    pub fn try_lock(&self) -> Option<LockGuard<T>> {
+        self.0.try_lock()
+    }
+
+    #[cfg(not(parallel_queries))]
+    #[inline(always)]
+    pub fn try_lock(&self) -> Option<LockGuard<T>> {
+        self.0.try_borrow_mut().ok()
+    }
+
     #[cfg(parallel_queries)]
     #[inline(always)]
     pub fn lock(&self) -> LockGuard<T> {