From 660a7be134e9264e93b0f12165fb7b6e528689af Mon Sep 17 00:00:00 2001
From: Jason O'Donnell <2160810+jasonodonnell@users.noreply.github.com>
Date: Mon, 29 Nov 2021 14:54:00 -0500
Subject: [PATCH] sdk/queue: move lock before checking queue length (#13146)

* sdk/queue: move lock before checking queue length

* Add changelog
---
 changelog/13146.txt         | 3 +++
 sdk/queue/priority_queue.go | 8 ++++----
 2 files changed, 7 insertions(+), 4 deletions(-)
 create mode 100644 changelog/13146.txt

diff --git a/changelog/13146.txt b/changelog/13146.txt
new file mode 100644
index 000000000..6bbe85e35
--- /dev/null
+++ b/changelog/13146.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+sdk/queue: move lock before length check to prevent panics.
+```
\ No newline at end of file
diff --git a/sdk/queue/priority_queue.go b/sdk/queue/priority_queue.go
index a0fda087f..399484177 100644
--- a/sdk/queue/priority_queue.go
+++ b/sdk/queue/priority_queue.go
@@ -85,13 +85,13 @@ func (pq *PriorityQueue) Len() int {
 // wrapper/convenience method that calls heap.Pop, so consumers do not need to
 // invoke heap functions directly
 func (pq *PriorityQueue) Pop() (*Item, error) {
-	if pq.Len() == 0 {
-		return nil, ErrEmpty
-	}
-
 	pq.lock.Lock()
 	defer pq.lock.Unlock()
 
+	if pq.data.Len() == 0 {
+		return nil, ErrEmpty
+	}
+
 	item := heap.Pop(&pq.data).(*Item)
 	delete(pq.dataMap, item.Key)
 	return item, nil