fix race condition when context is canceled (#1562)

methane · web-flow · commit d86c4527bae9 · 2024-03-17T13:30:21.000+09:00
Fix #1559.
diff --git a/connection.go b/connection.go
@@ -138,7 +138,7 @@ func (mc *mysqlConn) Close() (err error) {
 	}
 
 	mc.cleanup()
-
+	mc.clearResult()
 	return
 }
 
@@ -153,13 +153,16 @@ func (mc *mysqlConn) cleanup() {
 
 	// Makes cleanup idempotent
 	close(mc.closech)
-	if mc.netConn == nil {
+	nc := mc.netConn
+	if nc == nil {
 		return
 	}
-	if err := mc.netConn.Close(); err != nil {
+	if err := nc.Close(); err != nil {
 		mc.log(err)
 	}
-	mc.clearResult()
+	// This function can be called from multiple goroutines.
+	// So we can not mc.clearResult() here.
+	// Caller should do it if they are in safe goroutine.
 }
 
 func (mc *mysqlConn) error() error {

Original file line number	Diff line number	Diff line change
`@@ -138,7 +138,7 @@ func (mc *mysqlConn) Close() (err error) {`
`138`	`138`	`}`
`139`	`139`
`140`	`140`	`mc.cleanup()`
`141`		`-`
	`141`	`+ mc.clearResult()`
`142`	`142`	`return`
`143`	`143`	`}`
`144`	`144`
`@@ -153,13 +153,16 @@ func (mc *mysqlConn) cleanup() {`
`153`	`153`
`154`	`154`	`// Makes cleanup idempotent`
`155`	`155`	`close(mc.closech)`
`156`		`- if mc.netConn == nil {`
	`156`	`+ nc := mc.netConn`
	`157`	`+ if nc == nil {`
`157`	`158`	`return`
`158`	`159`	`}`
`159`		`- if err := mc.netConn.Close(); err != nil {`
	`160`	`+ if err := nc.Close(); err != nil {`
`160`	`161`	`mc.log(err)`
`161`	`162`	`}`
`162`		`- mc.clearResult()`
	`163`	`+ // This function can be called from multiple goroutines.`
	`164`	`+ // So we can not mc.clearResult() here.`
	`165`	`+ // Caller should do it if they are in safe goroutine.`
`163`	`166`	`}`
`164`	`167`
`165`	`168`	`func (mc *mysqlConn) error() error {`