From 512def40e821774aa1618519c4a6b61fb8b0b33e Mon Sep 17 00:00:00 2001
From: James M Snell <jasnell@gmail.com>
Date: Mon, 26 Apr 2021 06:50:40 -0700
Subject: [PATCH] perf_hooks: fix PerformanceObserver 'gc' crash

Signed-off-by: James M Snell <jasnell@gmail.com>
Fixes: https://github.com/nodejs/node/issues/38412
---
 lib/internal/perf/observe.js                 |  7 ++++++-
 test/parallel/test-performanceobserver-gc.js | 17 +++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/parallel/test-performanceobserver-gc.js

diff --git a/lib/internal/perf/observe.js b/lib/internal/perf/observe.js
index 4d71666882a3ba..c96925c723f64e 100644
--- a/lib/internal/perf/observe.js
+++ b/lib/internal/perf/observe.js
@@ -72,6 +72,8 @@ const kDeprecationMessage =
 const kTypeSingle = 0;
 const kTypeMultiple = 1;
 
+let gcTrackingInstalled = false;
+
 const kSupportedEntryTypes = ObjectFreeze([
   'function',
   'gc',
@@ -124,8 +126,11 @@ function maybeIncrementObserverCount(type) {
 
   if (observerType !== undefined) {
     observerCounts[observerType]++;
-    if (observerType === NODE_PERFORMANCE_ENTRY_TYPE_GC)
+    if (!gcTrackingInstalled &&
+        observerType === NODE_PERFORMANCE_ENTRY_TYPE_GC) {
       installGarbageCollectionTracking();
+      gcTrackingInstalled = true;
+    }
   }
 }
 
diff --git a/test/parallel/test-performanceobserver-gc.js b/test/parallel/test-performanceobserver-gc.js
new file mode 100644
index 00000000000000..fe9397631c2d42
--- /dev/null
+++ b/test/parallel/test-performanceobserver-gc.js
@@ -0,0 +1,17 @@
+'use strict';
+
+require('../common');
+
+// Verifies that setting up two observers to listen
+// to gc performance does not crash.
+
+const {
+  PerformanceObserver,
+} = require('perf_hooks');
+
+// We don't actually care if the callback is ever invoked in this test
+const obs = new PerformanceObserver(() => {});
+const obs2 = new PerformanceObserver(() => {});
+
+obs.observe({ type: 'gc' });
+obs2.observe({ type: 'gc' });