session: fix update process info will data race with expensive-query …

…check (#50696)

close #50607

pkg/session/session.go

@@ -1558,9 +1558,12 @@ func (s *session) UpdateProcessInfo() {
 	if pi == nil || pi.CurTxnStartTS != 0 {
 		return
 	}
+	// do not modify this two fields in place, see issue: issues/50607
+	shallowCP := pi.Clone()
 	// Update the current transaction start timestamp.
-	pi.CurTxnStartTS = s.sessionVars.TxnCtx.StartTS
-	pi.CurTxnCreateTime = s.sessionVars.TxnCtx.CreateTime
+	shallowCP.CurTxnStartTS = s.sessionVars.TxnCtx.StartTS
+	shallowCP.CurTxnCreateTime = s.sessionVars.TxnCtx.CreateTime
+	s.processInfo.Store(shallowCP)
 }
 
 func (s *session) getOomAlarmVariablesInfo() util.OOMAlarmVariablesInfo {

pkg/util/BUILD.bazel

@@ -62,6 +62,7 @@ go_test(
         "main_test.go",
         "misc_test.go",
         "prefix_helper_test.go",
+        "processinfo_test.go",
         "security_test.go",
         "urls_test.go",
         "util_test.go",

pkg/util/processinfo.go

@@ -73,6 +73,12 @@ type ProcessInfo struct {
 	RedactSQL        bool
 }
 
+// Clone return a shallow clone copy of this processInfo.
+func (pi *ProcessInfo) Clone() *ProcessInfo {
+	cp := *pi
+	return &cp
+}
+
 // ToRowForShow returns []interface{} for the row data of "SHOW [FULL] PROCESSLIST".
 func (pi *ProcessInfo) ToRowForShow(full bool) []interface{} {
 	var info interface{}

pkg/util/processinfo_test.go

@@ -0,0 +1,67 @@
+// Copyright 2024 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package util
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"github.com/pingcap/tidb/pkg/sessionctx/stmtctx"
+	"github.com/pingcap/tidb/pkg/util/memory"
+	"github.com/stretchr/testify/require"
+)
+
+func MyFunc(interface{}) map[string]uint64 {
+	return nil
+}
+
+func TestProcessInfoShallowCP(t *testing.T) {
+	mem := memory.NewTracker(-1, -1)
+	mem.Consume(1<<30 + 1<<29 + 1<<28 + 1<<27)
+
+	var refCount stmtctx.ReferenceCount = 0
+	info := &ProcessInfo{
+		ID:                233,
+		User:              "PingCAP",
+		Host:              "127.0.0.1",
+		DB:                "Database",
+		Info:              "select * from table where a > 1",
+		CurTxnStartTS:     23333,
+		StatsInfo:         MyFunc,
+		StmtCtx:           stmtctx.NewStmtCtx(),
+		RefCountOfStmtCtx: &refCount,
+		MemTracker:        mem,
+		RedactSQL:         false,
+		SessionAlias:      "alias123",
+	}
+
+	cp := info.Clone()
+	require.False(t, cp == info)
+	require.True(t, cp.ID == info.ID)
+	require.True(t, cp.User == info.User)
+	require.True(t, cp.Host == info.Host)
+	require.True(t, cp.DB == info.DB)
+	require.True(t, cp.Info == info.Info)
+	require.True(t, cp.CurTxnStartTS == info.CurTxnStartTS)
+	// reflect.DeepEqual couldn't cmp two function pointer.
+	require.True(t, reflect.ValueOf(cp.StatsInfo).Pointer() == reflect.ValueOf(info.StatsInfo).Pointer())
+	fmt.Println(reflect.ValueOf(cp.StatsInfo).Pointer(), reflect.ValueOf(info.StatsInfo).Pointer())
+	require.True(t, cp.StmtCtx == info.StmtCtx)
+	require.True(t, cp.RefCountOfStmtCtx == info.RefCountOfStmtCtx)
+	require.True(t, cp.MemTracker == info.MemTracker)
+	require.True(t, cp.RedactSQL == info.RedactSQL)
+	require.True(t, cp.SessionAlias == info.SessionAlias)
+}