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database/sql: possible race condition when canceling Tx with open Rows #20622

Closed
kardianos opened this issue Jun 9, 2017 · 4 comments
Closed

database/sql: possible race condition when canceling Tx with open Rows #20622

kardianos opened this issue Jun 9, 2017 · 4 comments
Labels
FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.9

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@kardianos
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Contributor

The following program produces a race condition for both mysql and sqlserver drivers. While this could be a common issue with both drivers, it is also possible it is an issue with database/sql.

To reproduce:

package main

import (
	"context"
	"database/sql"
	"flag"
	"fmt"
	"time"

	_ "github.com/denisenkom/go-mssqldb"
	_ "github.com/go-sql-driver/mysql"
	"github.com/golang/glog"
)

var (
	driverFlag = flag.String("driver", "mysql", "SQL Driver Name")
	dbFlag     = flag.String("dsn", "", "DSN")
)

func main() {
	flag.Parse()
	ctx, cancel := context.WithCancel(context.Background())
	db, err := sql.Open(*driverFlag, *dbFlag)
	if err != nil {
		glog.Exitf("failed to Open(%q): %v", *dbFlag, err)
	}
	defer db.Close()

	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		glog.Exitf("failed to BeginTx(): %v", err)
	}

	sql1 := `declare @vv table(ID bigint primary key identity(1,1), Item int);

insert into @vv (Item)
SELECT n = ones.n + 10*tens.n
FROM (VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) ones(n),
	 (VALUES(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) tens(n)
where 1=1
	and ones.n + 10*tens.n between 10 and 100
ORDER BY 1;

select * from @vv;`

	sql2 := `SELECT id, val FROM test;`

	sqlUse := sql2
	if *driverFlag == "sqlserver" {
		sqlUse = sql1
	}

	rows, err := tx.Query(sqlUse)
	if err != nil {
		glog.Exitf("failed to Query(): %v", err)
	}

	count := 0
	for rows.Next() {
		count++
		var val2, val3 int64
		if err := rows.Scan(&val2, &val3); err != nil {
			glog.Exitf("failed to Scan(): %v", err)
		}
		fmt.Printf("%d %d\n", val2, val3)

		if count == 1 {
			glog.Errorf("cancel the context out from under the transaction!")
			cancel()
		}
		time.Sleep(100 * time.Millisecond)
	}
	rows.Close()
	tx.Commit()
}

Race report using sqlserver driver

==================
WARNING: DATA RACE
Write at 0x00c420278148 by goroutine 22:
  github.com/denisenkom/go-mssqldb.sendAttention()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:127 +0x215
  github.com/denisenkom/go-mssqldb.(*parseResp).sendAttention()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:645 +0x64
  github.com/denisenkom/go-mssqldb.(*parseResp).iter()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:688 +0xa81
  github.com/denisenkom/go-mssqldb.processResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:761 +0x16b

Previous write at 0x00c420278148 by goroutine 21:
  github.com/denisenkom/go-mssqldb.sendRollbackXact()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:127 +0x29d
  github.com/denisenkom/go-mssqldb.(*MssqlConn).sendRollbackRequest()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:112 +0x42f
  github.com/denisenkom/go-mssqldb.(*MssqlConn).Rollback()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:101 +0x3c
  database/sql.(*Tx).rollback.func1()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1767 +0x6e
  database/sql.withLock()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2814 +0x76
  database/sql.(*Tx).rollback()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1766 +0x10a
  database/sql.(*Tx).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1678 +0x7d

Goroutine 22 (running) created at:
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).processQueryResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:328 +0x11e
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).queryContext()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:322 +0xe5
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).QueryContext()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql_go18.go:66 +0x241
  database/sql.ctxDriverStmtQuery()
      /home/daniel/code/go-cl/src/database/sql/ctxutil.go:83 +0x2e8
  database/sql.rowsiFromStatement()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2256 +0x29d
  database/sql.(*DB).queryDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1333 +0x387
  database/sql.(*Tx).QueryContext()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1963 +0x1da
  database/sql.(*Tx).Query()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1968 +0xa8
  main.main()
      /home/daniel/src/test/trillian617/main.go:61 +0x3e8

Goroutine 21 (running) created at:
  database/sql.(*DB).beginDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1428 +0x359
  database/sql.(*DB).begin()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1403 +0x130
  database/sql.(*DB).BeginTx()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1381 +0xa3
  main.main()
      /home/daniel/src/test/trillian617/main.go:37 +0x2bd
==================
==================
WARNING: DATA RACE
Read at 0x00c4202bc000 by goroutine 21:
  runtime.slicecopy()
      /home/daniel/code/go-cl/src/runtime/slice.go:160 +0x0
  crypto/tls.(*Conn).writeRecordLocked()
      /home/daniel/code/go-cl/src/crypto/tls/conn.go:907 +0x44a
  crypto/tls.(*Conn).Write()
      /home/daniel/code/go-cl/src/crypto/tls/conn.go:1068 +0x236
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).flush()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:76 +0x213
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).FinishPacket()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:132 +0x80
  github.com/denisenkom/go-mssqldb.sendRollbackXact()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/tran.go:110 +0x446
  github.com/denisenkom/go-mssqldb.(*MssqlConn).sendRollbackRequest()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:112 +0x42f
  github.com/denisenkom/go-mssqldb.(*MssqlConn).Rollback()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:101 +0x3c
  database/sql.(*Tx).rollback.func1()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1767 +0x6e
  database/sql.withLock()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2814 +0x76
  database/sql.(*Tx).rollback()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1766 +0x10a
  database/sql.(*Tx).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1678 +0x7d

Previous write at 0x00c4202bc004 by goroutine 22:
  github.com/denisenkom/go-mssqldb.sendAttention()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:123 +0x108
  github.com/denisenkom/go-mssqldb.(*parseResp).sendAttention()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:645 +0x64
  github.com/denisenkom/go-mssqldb.(*parseResp).iter()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:688 +0xa81
  github.com/denisenkom/go-mssqldb.processResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:761 +0x16b

Goroutine 21 (running) created at:
  database/sql.(*DB).beginDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1428 +0x359
  database/sql.(*DB).begin()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1403 +0x130
  database/sql.(*DB).BeginTx()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1381 +0xa3
  main.main()
      /home/daniel/src/test/trillian617/main.go:37 +0x2bd

Goroutine 22 (running) created at:
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).processQueryResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:328 +0x11e
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).queryContext()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:322 +0xe5
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).QueryContext()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql_go18.go:66 +0x241
  database/sql.ctxDriverStmtQuery()
      /home/daniel/code/go-cl/src/database/sql/ctxutil.go:83 +0x2e8
  database/sql.rowsiFromStatement()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2256 +0x29d
  database/sql.(*DB).queryDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1333 +0x387
  database/sql.(*Tx).QueryContext()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1963 +0x1da
  database/sql.(*Tx).Query()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1968 +0xa8
  main.main()
      /home/daniel/src/test/trillian617/main.go:61 +0x3e8
==================
==================
WARNING: DATA RACE
Write at 0x00c4202bc001 by goroutine 22:
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).FinishPacket()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:131 +0x60
  github.com/denisenkom/go-mssqldb.sendAttention()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/tds.go:653 +0x229
  github.com/denisenkom/go-mssqldb.(*parseResp).sendAttention()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:645 +0x64
  github.com/denisenkom/go-mssqldb.(*parseResp).iter()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:688 +0xa81
  github.com/denisenkom/go-mssqldb.processResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:761 +0x16b

Previous write at 0x00c4202bc001 by goroutine 21:
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).FinishPacket()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:131 +0x60
  github.com/denisenkom/go-mssqldb.sendRollbackXact()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/tran.go:110 +0x446
  github.com/denisenkom/go-mssqldb.(*MssqlConn).sendRollbackRequest()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:112 +0x42f
  github.com/denisenkom/go-mssqldb.(*MssqlConn).Rollback()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:101 +0x3c
  database/sql.(*Tx).rollback.func1()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1767 +0x6e
  database/sql.withLock()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2814 +0x76
  database/sql.(*Tx).rollback()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1766 +0x10a
  database/sql.(*Tx).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1678 +0x7d

Goroutine 22 (running) created at:
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).processQueryResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:328 +0x11e
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).queryContext()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql.go:322 +0xe5
  github.com/denisenkom/go-mssqldb.(*MssqlStmt).QueryContext()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/mssql_go18.go:66 +0x241
  database/sql.ctxDriverStmtQuery()
      /home/daniel/code/go-cl/src/database/sql/ctxutil.go:83 +0x2e8
  database/sql.rowsiFromStatement()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2256 +0x29d
  database/sql.(*DB).queryDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1333 +0x387
  database/sql.(*Tx).QueryContext()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1963 +0x1da
  database/sql.(*Tx).Query()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1968 +0xa8
  main.main()
      /home/daniel/src/test/trillian617/main.go:61 +0x3e8

Goroutine 21 (running) created at:
  database/sql.(*DB).beginDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1428 +0x359
  database/sql.(*DB).begin()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1403 +0x130
  database/sql.(*DB).BeginTx()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1381 +0xa3
  main.main()
      /home/daniel/src/test/trillian617/main.go:37 +0x2bd
==================
==================
WARNING: DATA RACE
Write at 0x00c4202bd008 by goroutine 27:
  runtime.slicecopy()
      /home/daniel/code/go-cl/src/runtime/slice.go:160 +0x0
  crypto/tls.(*Conn).Read()
      /home/daniel/code/go-cl/src/crypto/tls/conn.go:503 +0x377
  io.ReadAtLeast()
      /home/daniel/code/go-cl/src/io/io.go:307 +0x93
  io.ReadFull()
      /home/daniel/code/go-cl/src/io/io.go:325 +0x72
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).readNextPacket()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:149 +0x448
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).BeginRead()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:161 +0x3c
  github.com/denisenkom/go-mssqldb.processSingleResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:531 +0xdd

Previous read at 0x00c4202bd008 by goroutine 26:
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).ReadByte()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:178 +0xb5
  github.com/denisenkom/go-mssqldb.(*tdsBuffer).byte()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/buf.go:184 +0x38
  github.com/denisenkom/go-mssqldb.processSingleResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:545 +0x1ac

Goroutine 27 (running) created at:
  github.com/denisenkom/go-mssqldb.processResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:756 +0x201

Goroutine 26 (finished) created at:
  github.com/denisenkom/go-mssqldb.processResponse()
      /home/daniel/src/github.com/denisenkom/go-mssqldb/token.go:756 +0x201
==================
Found 4 data race(s)

Race report using the mysql driver

==================
WARNING: DATA RACE
Write at 0x00c4200b4030 by goroutine 10:
  github.com/go-sql-driver/mysql.(*buffer).readNext()
      /home/daniel/src/github.com/go-sql-driver/mysql/buffer.go:104 +0xf5
  github.com/go-sql-driver/mysql.(*mysqlConn).readPacket()
      /home/daniel/src/github.com/go-sql-driver/mysql/packets.go:31 +0xd4
  github.com/go-sql-driver/mysql.(*mysqlConn).readUntilEOF()
      /home/daniel/src/github.com/go-sql-driver/mysql/packets.go:768 +0x50
  github.com/go-sql-driver/mysql.(*mysqlRows).Close()
      /home/daniel/src/github.com/go-sql-driver/mysql/rows.go:67 +0x7d
  github.com/go-sql-driver/mysql.(*textRows).Close()
      <autogenerated>:1 +0x43
  database/sql.(*Rows).close()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2703 +0x15b
  database/sql.(*Rows).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2391 +0x14c

Previous read at 0x00c4200b4030 by goroutine 9:
  github.com/go-sql-driver/mysql.(*mysqlConn).writeCommandPacketStr()
      /home/daniel/src/github.com/go-sql-driver/mysql/buffer.go:113 +0x73
  github.com/go-sql-driver/mysql.(*mysqlConn).exec()
      /home/daniel/src/github.com/go-sql-driver/mysql/connection.go:292 +0x55
  github.com/go-sql-driver/mysql.(*mysqlTx).Rollback()
      /home/daniel/src/github.com/go-sql-driver/mysql/transaction.go:28 +0xfb
  database/sql.(*Tx).rollback.func1()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1767 +0x6e
  database/sql.withLock()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2814 +0x76
  database/sql.(*Tx).rollback()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1766 +0x10a
  database/sql.(*Tx).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1678 +0x7d

Goroutine 10 (running) created at:
  database/sql.(*Rows).initContextClose()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2375 +0xdd
  database/sql.(*DB).queryDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1317 +0xb7f
  database/sql.(*Tx).QueryContext()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1963 +0x1da
  database/sql.(*Tx).Query()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1968 +0xa8
  main.main()
      /home/daniel/src/test/trillian617/main.go:40 +0x389

Goroutine 9 (running) created at:
  database/sql.(*DB).beginDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1428 +0x359
  database/sql.(*DB).begin()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1403 +0x130
  database/sql.(*DB).BeginTx()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1381 +0xa3
  main.main()
      /home/daniel/src/test/trillian617/main.go:35 +0x297
==================
==================
WARNING: DATA RACE
Read at 0x00c4200b4086 by goroutine 10:
  github.com/go-sql-driver/mysql.(*mysqlConn).readPacket()
      /home/daniel/src/github.com/go-sql-driver/mysql/packets.go:42 +0x1bd
  github.com/go-sql-driver/mysql.(*mysqlConn).readUntilEOF()
      /home/daniel/src/github.com/go-sql-driver/mysql/packets.go:768 +0x50
  github.com/go-sql-driver/mysql.(*mysqlRows).Close()
      /home/daniel/src/github.com/go-sql-driver/mysql/rows.go:67 +0x7d
  github.com/go-sql-driver/mysql.(*textRows).Close()
      <autogenerated>:1 +0x43
  database/sql.(*Rows).close()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2703 +0x15b
  database/sql.(*Rows).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2391 +0x14c

Previous write at 0x00c4200b4086 by goroutine 9:
  github.com/go-sql-driver/mysql.(*mysqlConn).writeCommandPacketStr()
      /home/daniel/src/github.com/go-sql-driver/mysql/packets.go:425 +0x57
  github.com/go-sql-driver/mysql.(*mysqlConn).exec()
      /home/daniel/src/github.com/go-sql-driver/mysql/connection.go:292 +0x55
  github.com/go-sql-driver/mysql.(*mysqlTx).Rollback()
      /home/daniel/src/github.com/go-sql-driver/mysql/transaction.go:28 +0xfb
  database/sql.(*Tx).rollback.func1()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1767 +0x6e
  database/sql.withLock()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2814 +0x76
  database/sql.(*Tx).rollback()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1766 +0x10a
  database/sql.(*Tx).awaitDone()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1678 +0x7d

Goroutine 10 (running) created at:
  database/sql.(*Rows).initContextClose()
      /home/daniel/code/go-cl/src/database/sql/sql.go:2375 +0xdd
  database/sql.(*DB).queryDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1317 +0xb7f
  database/sql.(*Tx).QueryContext()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1963 +0x1da
  database/sql.(*Tx).Query()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1968 +0xa8
  main.main()
      /home/daniel/src/test/trillian617/main.go:40 +0x389

Goroutine 9 (running) created at:
  database/sql.(*DB).beginDC()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1428 +0x359
  database/sql.(*DB).begin()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1403 +0x130
  database/sql.(*DB).BeginTx()
      /home/daniel/code/go-cl/src/database/sql/sql.go:1381 +0xa3
  main.main()
      /home/daniel/src/test/trillian617/main.go:35 +0x297
==================

orig from google/trillian#617
@kardianos kardianos added this to the Go1.9 milestone Jun 9, 2017
@kardianos kardianos self-assigned this Jun 9, 2017
@bradfitz bradfitz added the NeedsFix The path to resolution is known, but the work has not been done. label Jun 9, 2017
@bradfitz
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bradfitz commented Jun 9, 2017

We want to do a beta early next week. Can you get a fix out soon?

@kardianos
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I should be able to look into it this afternoon.

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CL https://golang.org/cl/45275 mentions this issue.

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kardianos commented Jun 11, 2017 •
edited

After instrumenting the fakeConn with a var that gets read and written to on each call, the concurrency test blew up on the race try bot, though I'm having trouble replicating it locally. This was after I fixed the above sql interface race.
https://storage.googleapis.com/go-build-log/495e96e8/linux-amd64-race_7e99dc4a.log

==================
WARNING: DATA RACE
Read at 0x00c4202869d0 by goroutine 145:
  database/sql.(*rowsCursor).Next()
      /tmp/workdir/go/src/database/sql/fakedb_test.go:958 +0x15d
  database/sql.(*Rows).nextLocked()
      /tmp/workdir/go/src/database/sql/sql.go:2418 +0xd1
  database/sql.(*Rows).Next.func1()
      /tmp/workdir/go/src/database/sql/sql.go:2403 +0x57
  database/sql.withLock()
      /tmp/workdir/go/src/database/sql/sql.go:2816 +0x76
  database/sql.(*Rows).Next()
      /tmp/workdir/go/src/database/sql/sql.go:2402 +0xe8
  database/sql.(*concurrentTxStmtQueryTest).test()
      /tmp/workdir/go/src/database/sql/sql_test.go:2939 +0x14e
  database/sql.doConcurrentTest.func1()
      /tmp/workdir/go/src/database/sql/sql_test.go:3039 +0x7c

Previous write at 0x00c4202869d0 by goroutine 99:
  database/sql.(*fakeStmt).QueryContext()
      /tmp/workdir/go/src/database/sql/fakedb_test.go:773 +0x2e0
  database/sql.ctxDriverStmtQuery()
      /tmp/workdir/go/src/database/sql/ctxutil.go:83 +0x2e8
  database/sql.rowsiFromStatement()
      /tmp/workdir/go/src/database/sql/sql.go:2256 +0x29d
  database/sql.(*Stmt).QueryContext()
      /tmp/workdir/go/src/database/sql/sql.go:2194 +0x28b
  database/sql.(*Stmt).Query()
      /tmp/workdir/go/src/database/sql/sql.go:2232 +0x88
  database/sql.(*concurrentTxStmtQueryTest).test()
      /tmp/workdir/go/src/database/sql/sql_test.go:2932 +0x79
  database/sql.doConcurrentTest.func1()
      /tmp/workdir/go/src/database/sql/sql_test.go:3039 +0x7c

Goroutine 145 (running) created at:
  database/sql.doConcurrentTest()
      /tmp/workdir/go/src/database/sql/sql_test.go:3037 +0x2bd
  database/sql.TestConcurrency()
      /tmp/workdir/go/src/database/sql/sql_test.go:3241 +0x1ee
  testing.tRunner()
      /tmp/workdir/go/src/testing/testing.go:747 +0x16c

Goroutine 99 (running) created at:
  database/sql.doConcurrentTest()
      /tmp/workdir/go/src/database/sql/sql_test.go:3037 +0x2bd
  database/sql.TestConcurrency()
      /tmp/workdir/go/src/database/sql/sql_test.go:3241 +0x1ee
  testing.tRunner()
      /tmp/workdir/go/src/testing/testing.go:747 +0x16c
==================
==================
WARNING: DATA RACE
Read at 0x00c4202869d0 by goroutine 14:
  database/sql.(*rowsCursor).Next()
      /tmp/workdir/go/src/database/sql/fakedb_test.go:958 +0x15d
  database/sql.(*Rows).nextLocked()
      /tmp/workdir/go/src/database/sql/sql.go:2418 +0xd1
  database/sql.(*Rows).Next.func1()
      /tmp/workdir/go/src/database/sql/sql.go:2403 +0x57
  database/sql.withLock()
      /tmp/workdir/go/src/database/sql/sql.go:2816 +0x76
  database/sql.(*Rows).Next()
      /tmp/workdir/go/src/database/sql/sql.go:2402 +0xe8
  database/sql.(*concurrentTxStmtQueryTest).test()
      /tmp/workdir/go/src/database/sql/sql_test.go:2939 +0x14e
  database/sql.doConcurrentTest.func1()
      /tmp/workdir/go/src/database/sql/sql_test.go:3039 +0x7c

Previous write at 0x00c4202869d0 by goroutine 99:
  database/sql.(*fakeStmt).QueryContext()
      /tmp/workdir/go/src/database/sql/fakedb_test.go:773 +0x2e0
  database/sql.ctxDriverStmtQuery()
      /tmp/workdir/go/src/database/sql/ctxutil.go:83 +0x2e8
  database/sql.rowsiFromStatement()
      /tmp/workdir/go/src/database/sql/sql.go:2256 +0x29d
  database/sql.(*Stmt).QueryContext()
      /tmp/workdir/go/src/database/sql/sql.go:2194 +0x28b
  database/sql.(*Stmt).Query()
      /tmp/workdir/go/src/database/sql/sql.go:2232 +0x88
  database/sql.(*concurrentTxStmtQueryTest).test()
      /tmp/workdir/go/src/database/sql/sql_test.go:2932 +0x79
  database/sql.doConcurrentTest.func1()
      /tmp/workdir/go/src/database/sql/sql_test.go:3039 +0x7c

Goroutine 14 (running) created at:
  database/sql.doConcurrentTest()
      /tmp/workdir/go/src/database/sql/sql_test.go:3037 +0x2bd
  database/sql.TestConcurrency()
      /tmp/workdir/go/src/database/sql/sql_test.go:3241 +0x1ee
  testing.tRunner()
      /tmp/workdir/go/src/testing/testing.go:747 +0x16c

Goroutine 99 (running) created at:
  database/sql.doConcurrentTest()
      /tmp/workdir/go/src/database/sql/sql_test.go:3037 +0x2bd
  database/sql.TestConcurrency()
      /tmp/workdir/go/src/database/sql/sql_test.go:3241 +0x1ee
  testing.tRunner()
      /tmp/workdir/go/src/testing/testing.go:747 +0x16c
==================
--- FAIL: TestConcurrency (0.07s)
	testing.go:700: race detected during execution of test

@kardianos kardianos mentioned this issue Jun 12, 2017
Closed
@golang golang locked and limited conversation to collaborators Jun 12, 2018
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