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database/sql: prevent Tx.rollback from racing Tx.close

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Previously Tx.done was being set in close, but in a Tx
rollback and Commit are the real closing methods,
and Tx.close is just a helper common to both. Prior to this
change a multiple rollback statements could be called, one
would enter close and begin closing it while the other was
still in rollback breaking it. Fix that by setting done
in rollback and Commit, not in Tx.close.

Fixes #18429

Change-Id: Ie274f60c2aa6a4a5aa38e55109c05ea9d4fe0223
Reviewed-on: https://go-review.googlesource.com/34716
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Daniel Theophanes 2016-12-26 11:33:46 -08:00 • committed by Brad Fitzpatrick
parent f78cd569f5
commit 9def857072
2 changed files with 52 additions and 5 deletions
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9
src/database/sql/sql.go
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@ -1421,10 +1421,9 @@ func (tx *Tx) isDone() bool {
// that has already been committed or rolled back.
var ErrTxDone = errors.New("sql: Transaction has already been committed or rolled back")
// close returns the connection to the pool and
// must only be called by Tx.rollback or Tx.Commit.
func (tx *Tx) close(err error) {
if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
panic("double close") // internal error
}
tx.db.putConn(tx.dc, err)
tx.cancel()
tx.dc = nil
@ -1449,7 +1448,7 @@ func (tx *Tx) closePrepared() {
// Commit commits the transaction.
func (tx *Tx) Commit() error {
if tx.isDone() {
if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
return ErrTxDone
}
select {
@ -1471,7 +1470,7 @@ func (tx *Tx) Commit() error {
// rollback aborts the transaction and optionally forces the pool to discard
// the connection.
func (tx *Tx) rollback(discardConn bool) error {
if tx.isDone() {
if !atomic.CompareAndSwapInt32(&tx.done, 0, 1) {
return ErrTxDone
}
var err error