From 3220b2ddc5968f494088a3a83ba0b69f449abab4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tibor=20K=C3=A1lm=C3=A1n?= <tiborkalman@alpaca.markets>
Date: Fri, 3 Nov 2023 10:41:44 +0100
Subject: [PATCH 1/2] getAttrInfo race test

---
 ibmmq/ibmmq_test.go | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/ibmmq/ibmmq_test.go b/ibmmq/ibmmq_test.go
index 7e5f68e..16722e9 100644
--- a/ibmmq/ibmmq_test.go
+++ b/ibmmq/ibmmq_test.go
@@ -319,3 +319,22 @@ func TestNewMQDLHWithMQMD(t *testing.T) {
 		t.Fail()
 	}
 }
+
+func TestGetAttrInfoConcurrentCalls(t *testing.T) {
+	// NOTE: This test should be run with `go test -race`.
+	attrs := []int32{
+		MQCA_BACKOUT_REQ_Q_NAME,
+		MQIA_BACKOUT_THRESHOLD,
+	}
+	count := 1_000
+	doneCh := make(chan struct{}, count)
+	for i := 0; i < count; i++ {
+		go func() {
+			getAttrInfo(attrs)
+			doneCh <- struct{}{}
+		}()
+	}
+	for i := 0; i < count; i++ {
+		<-doneCh
+	}
+}

From 2fdc74158e2a68f86cbf1f0a06749747df1aa529 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tibor=20K=C3=A1lm=C3=A1n?= <tiborkalman@alpaca.markets>
Date: Fri, 3 Nov 2023 10:42:25 +0100
Subject: [PATCH 2/2] Use sync.Once to ensure mqInqLength is initialized once

---
 ibmmq/mqiattrs.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/ibmmq/mqiattrs.go b/ibmmq/mqiattrs.go
index 90007c7..0e57470 100644
--- a/ibmmq/mqiattrs.go
+++ b/ibmmq/mqiattrs.go
@@ -61,6 +61,7 @@ import "C"
 import (
 	"fmt"
 	"os"
+	"sync"
 )
 
 /*
@@ -130,7 +131,7 @@ var mqInqLength = map[int32]int32{
 	C.MQCA_XMIT_Q_NAME:           C.MQ_Q_NAME_LENGTH,
 }
 
-var charAttrsAdded = false
+var charAttrsAddedOnce sync.Once
 
 /*
  * Return how many char & int attributes are in the list of selectors, and the
@@ -141,7 +142,7 @@ func getAttrInfo(attrs []int32) (int, int, int) {
 	var charAttrCount = 0
 	var intAttrCount = 0
 
-	if !charAttrsAdded {
+	charAttrsAddedOnce.Do(func() {
 		maxNewAttrs := C.MAX_NEW_MQCA_ATTRS
 		attrVals := make([]C.MQLONG, maxNewAttrs)
 		attrLens := make([]C.MQLONG, maxNewAttrs)
@@ -155,8 +156,7 @@ func getAttrInfo(attrs []int32) (int, int, int) {
 		for i := 0; i < addedAttrs; i++ {
 			mqInqLength[int32(attrVals[i])] = int32(attrLens[i])
 		}
-		charAttrsAdded = true
-	}
+	})
 
 	for i := 0; i < len(attrs); i++ {
 		if v, ok := mqInqLength[attrs[i]]; ok {