Data race between mysqlConn watcher and okHandler during context cancellation#1559
Description
Issue description
I have one goroutine running database transactions in a loop and another goroutine cancels the context being used. This leads to the data race shown below.
Example code
Execute with go test -v -race . -test.count 1000 -test.failfast -test.run 'TestRace'
funcTestRace(t*testing.T){r:=require.New(t) driver:= mysql.MySQLDriver{} connector, err:=driver.OpenConnector("root:SoupOrSecret@/mysql") r.NoError(err) db:=sql.OpenDB(connector) ctx, cancel:=context.WithTimeout(context.Background(), 5*time.Second) defercancel() triggerCancel:=make(chanstruct{}) done:=make(chanstruct{}) gofunc(){deferclose(done) didTrigger:=falseforctx.Err() ==nil{tx, err:=db.BeginTx(ctx, nil) iferrors.Is(err, context.Canceled){return } r.NoError(err) varoneinterr=tx.QueryRowContext(ctx, "SELECT 1").Scan(&one) iferrors.Is(err, context.Canceled){return } r.NoError(err) _=tx.Rollback() if!didTrigger{didTrigger=trueclose(triggerCancel) } } }() <-triggerCanceltime.Sleep(10*time.Millisecond) cancel() <-done }Error log
WARNING: DATA RACE Write at 0x00c000392458 by goroutine 28578: github.com/go-sql-driver/mysql.(*mysqlConn).clearResult() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/packets.go:630 +0x1c4 github.com/go-sql-driver/mysql.(*mysqlConn).cleanup() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/connection.go:156 +0x1a4 github.com/go-sql-driver/mysql.(*mysqlConn).cancel() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/connection.go:441 +0x84 github.com/go-sql-driver/mysql.(*mysqlConn).startWatcher.func1() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/connection.go:628 +0x234 Previous read at 0x00c000392458 by goroutine 30352: github.com/go-sql-driver/mysql.(*okHandler).handleOkPacket() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/packets.go:650 +0xfd github.com/go-sql-driver/mysql.(*okHandler).readResultSetHeaderPacket() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/packets.go:536 +0x36f github.com/go-sql-driver/mysql.(*mysqlConn).exec() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/connection.go:336 +0x18d github.com/go-sql-driver/mysql.(*mysqlConn).begin() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/connection.go:121 +0x8a github.com/go-sql-driver/mysql.(*mysqlConn).BeginTx() /home/runner/go/pkg/mod/github.com/go-sql-driver/[email protected]/connection.go:498 +0x156 database/sql.ctxDriverBegin() /opt/hostedtoolcache/go/1.20.14/x64/src/database/sql/ctxutil.go:104 +0x105 database/sql.(*DB).beginDC.func1() /opt/hostedtoolcache/go/1.20.14/x64/src/database/sql/sql.go:1868 +0x156 database/sql.withLock() /opt/hostedtoolcache/go/1.20.14/x64/src/database/sql/sql.go:3405 +0xa2 database/sql.(*DB).beginDC() /opt/hostedtoolcache/go/1.20.14/x64/src/database/sql/sql.go:1864 +0x113 database/sql.(*DB).begin() /opt/hostedtoolcache/go/1.20.14/x64/src/database/sql/sql.go:1857 +0x104 database/sql.(*DB).BeginTx.func1() Configuration
Driver version (or git SHA): 1.8.0
Go version: 1.20.7 & 1.22.1
Server version: mysql-v8 & mariadb-v10
Server OS: Ubuntu 22.04 (an ubuntu-latest GitHub actions runner)