135 lines
4.1 KiB
Diff
135 lines
4.1 KiB
Diff
From c77418f4cac41c42566ca90921a1f928995cfba2 Mon Sep 17 00:00:00 2001
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From: Emmanuel T Odeke <emmanuel@orijtech.com>
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Date: Mon, 18 Jan 2021 16:18:11 -0800
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Subject: [PATCH 30/44] [release-branch.go1.15] database/sql: fix tx stmt
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deadlock when rollback
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Tx acquires tx.closemu W-lock and then acquires stmt.closemu.W-lock
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to fully close the transaction and associated prepared statement.
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Stmt query and execution run in reverse ways - acquires
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stmt.closemu.R-lock and then acquires tx.closemu.R-lock to grab tx
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connection, which may cause deadlock.
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Prevent the lock is held around tx.closePrepared to ensure no
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deadlock happens.
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Includes a test fix from CL 266097.
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Fixes #42884
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Updates #40985
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Updates #42259
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Change-Id: Id52737660ada3cebdfff6efc23366cdc3224b8e8
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Reviewed-on: https://go-review.googlesource.com/c/go/+/250178
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Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
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TryBot-Result: Go Bot <gobot@golang.org>
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Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
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Trust: Emmanuel Odeke <emmanuel@orijtech.com>
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(cherry picked from commit d4c1ad882973e407ff85b977f4ce5b9435451190)
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Reviewed-on: https://go-review.googlesource.com/c/go/+/284513
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Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
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Conflict:NA
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Reference:https://github.com/golang/go/commit/c77418f4cac41c42566ca90921a1f928995cfba2
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---
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src/database/sql/sql.go | 14 +++++++-------
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src/database/sql/sql_test.go | 28 ++++++++++++++++++++++++++++
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2 files changed, 35 insertions(+), 7 deletions(-)
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diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
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index b3d0653f5c..3d1367d28f 100644
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--- a/src/database/sql/sql.go
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+++ b/src/database/sql/sql.go
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@@ -2080,10 +2080,10 @@ func (tx *Tx) isDone() bool {
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// that has already been committed or rolled back.
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var ErrTxDone = errors.New("sql: transaction has already been committed or rolled back")
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-// closeLocked returns the connection to the pool and
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+// close returns the connection to the pool and
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// must only be called by Tx.rollback or Tx.Commit while
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-// closemu is Locked and tx already canceled.
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-func (tx *Tx) closeLocked(err error) {
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+// tx is already canceled and won't be executed concurrently.
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+func (tx *Tx) close(err error) {
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tx.releaseConn(err)
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tx.dc = nil
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tx.txi = nil
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@@ -2157,7 +2157,7 @@ func (tx *Tx) Commit() error {
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// to ensure no other connection has an active query.
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tx.cancel()
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tx.closemu.Lock()
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- defer tx.closemu.Unlock()
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+ tx.closemu.Unlock()
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var err error
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withLock(tx.dc, func() {
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@@ -2166,7 +2166,7 @@ func (tx *Tx) Commit() error {
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if err != driver.ErrBadConn {
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tx.closePrepared()
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}
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- tx.closeLocked(err)
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+ tx.close(err)
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return err
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}
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@@ -2189,7 +2189,7 @@ func (tx *Tx) rollback(discardConn bool) error {
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// to ensure no other connection has an active query.
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tx.cancel()
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tx.closemu.Lock()
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- defer tx.closemu.Unlock()
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+ tx.closemu.Unlock()
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var err error
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withLock(tx.dc, func() {
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@@ -2201,7 +2201,7 @@ func (tx *Tx) rollback(discardConn bool) error {
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if discardConn {
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err = driver.ErrBadConn
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}
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- tx.closeLocked(err)
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+ tx.close(err)
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return err
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}
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diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
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index 5727f0d8aa..d7d4642608 100644
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--- a/src/database/sql/sql_test.go
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+++ b/src/database/sql/sql_test.go
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@@ -2810,6 +2810,34 @@ func TestTxCannotCommitAfterRollback(t *testing.T) {
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}
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}
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+// Issue 40985 transaction statement deadlock while context cancel.
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+func TestTxStmtDeadlock(t *testing.T) {
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+ db := newTestDB(t, "people")
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+ defer closeDB(t, db)
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+
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+ ctx, cancel := context.WithTimeout(context.Background(), 5*time.Millisecond)
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+ defer cancel()
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+ tx, err := db.BeginTx(ctx, nil)
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+ if err != nil {
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+ t.Fatal(err)
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+ }
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+
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+ stmt, err := tx.Prepare("SELECT|people|name,age|age=?")
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+ if err != nil {
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+ t.Fatal(err)
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+ }
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+ // Run number of stmt queries to reproduce deadlock from context cancel
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+ for i := 0; i < 1e3; i++ {
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+ // Encounter any close related errors (e.g.. ErrTxDone, stmt is closed)
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+ // is expected due to context cancel.
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+ _, err = stmt.Query(1)
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+ if err != nil {
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+ break
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+ }
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+ }
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+ _ = tx.Rollback()
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+}
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+
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// Issue32530 encounters an issue where a connection may
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// expire right after it comes out of a used connection pool
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// even when a new connection is requested.
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--
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2.27.0
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