data race in Processinfo with index scan

[wshwsh12]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

In GenLogFields function, need to read info.StmtCtx.IndexNames, which may be modified in executor building phase.
GenLogFields:

tidb/util/util.go

Line 161 in 6f79794

indexNames = strings.ReplaceAll(fmt.Sprintf("%v", info.StmtCtx.IndexNames), " ", ",")

Build phase:

tidb/executor/builder.go

Line 3814 in 6f79794

sctx.IndexNames = append(sctx.IndexNames, is.Table.Name.O+":"+is.Index.Name.O)

This will cause a data race.

Test code:

func TestProcessInfoRaceWithIndexScan(t *testing.T) {
	store := testkit.CreateMockStore(t)
	tk := testkit.NewTestKit(t, store)
	tk.MustExec("use test;")
	tk.MustExec("drop table if exists t1;")
	tk.MustExec("create table t1(c1 int, c2 int, c3 int, c4 int, c5 int, key(c1), key(c2), key(c3), key(c4),key(c5));")
	insertStr := "insert into t1 values(0, 0, 0, 0 , 0)"
	for i := 1; i < 100; i++ {
		insertStr += fmt.Sprintf(", (%d, %d, %d, %d, %d)", i, i, i, i, i)
	}
	tk.MustExec(insertStr)

	tk.Session().SetSessionManager(&testkit.MockSessionManager{
		PS: []*util.ProcessInfo{tk.Session().ShowProcess()},
	})

	wg := sync.WaitGroup{}
	wg.Add(1)
	go func() {
		defer wg.Done()
		for true {
			ps := tk.Session().ShowProcess()
			util.GenLogFields(233, ps, true)
		}
	}()
	for i := 0; i <= 1000000; i++ {
		tk.MustQuery("select /*+ use_index(t1, c1) */ c1 from t1 where c1 = 0 union all select /*+ use_index(t1, c2) */ c2 from t1 where c2 = 0 union all select /*+ use_index(t1, c3) */ c3 from t1 where c3 = 0 ")
	}
	wg.Wait()
}

2. What did you expect to see? (Required)

No error, no race.

3. What did you see instead (Required)

Without -race flag:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x12 pc=0x1a0427c]

goroutine 14836 [running]:
fmt.(*buffer).writeString(...)
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:108
fmt.(*fmt).padString(0xc01c072020?, {0x12, 0x1})
        /home/wshwsh12/sdk/go1.20/src/fmt/format.go:110 +0x245
fmt.(*fmt).fmtS(0xc0051df3a0?, {0x12?, 0x4d570e0?})
        /home/wshwsh12/sdk/go1.20/src/fmt/format.go:359 +0x3f
fmt.(*pp).fmtString(0xc012e235f0?, {0x12?, 0x19f4280?}, 0x51df3b8?)
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:494 +0x86
fmt.(*pp).printValue(0xc012e235f0, {0x4d570e0?, 0xc01702f490?, 0x10?}, 0x76, 0x1)
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:804 +0xfc5
fmt.(*pp).printValue(0xc012e235f0, {0x4cf4be0?, 0xc017481080?, 0xc0051df7f8?}, 0x76, 0x0)
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:912 +0x15b3
fmt.(*pp).printArg(0xc012e235f0, {0x4cf4be0?, 0xc017481080}, 0x76)
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:759 +0x756
fmt.(*pp).doPrintf(0xc012e235f0, {0x54c57a2, 0x2}, {0xc0051dfba0?, 0x1, 0x1})
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:1077 +0x387
fmt.Sprintf({0x54c57a2, 0x2}, {0xc0051dfba0, 0x1, 0x1})
        /home/wshwsh12/sdk/go1.20/src/fmt/print.go:239 +0x59
github.com/pingcap/tidb/util.GenLogFields(0xe9, 0xc01703c580, 0x1)
        /home/wshwsh12/project/tidb/util/util.go:161 +0xb08

With -race flag:

==================
WARNING: DATA RACE
Write at 0x00c005259b30 by goroutine 75:
  github.com/pingcap/tidb/executor.(*executorBuilder).buildIndexReader()
      /home/wshwsh12/project/tidb/executor/builder.go:3768 +0x584
  github.com/pingcap/tidb/executor.(*executorBuilder).build()
      /home/wshwsh12/project/tidb/executor/builder.go:281 +0x17f9
  github.com/pingcap/tidb/executor.(*executorBuilder).buildUnionAll()
      /home/wshwsh12/project/tidb/executor/builder.go:2311 +0x15c
  github.com/pingcap/tidb/executor.(*executorBuilder).build()
      /home/wshwsh12/project/tidb/executor/builder.go:243 +0x119b
  github.com/pingcap/tidb/executor.(*ExecStmt).buildExecutor()
      /home/wshwsh12/project/tidb/executor/adapter.go:1174 +0x393
  github.com/pingcap/tidb/executor.(*ExecStmt).Exec()
      /home/wshwsh12/project/tidb/executor/adapter.go:523 +0x7f1
  github.com/pingcap/tidb/session.runStmt()
      /home/wshwsh12/project/tidb/session/session.go:2400 +0x4f8
  github.com/pingcap/tidb/session.(*session).ExecuteStmt()
      /home/wshwsh12/project/tidb/session/session.go:2250 +0x133c
  github.com/pingcap/tidb/testkit.(*TestKit).ExecWithContext()
      /home/wshwsh12/project/tidb/testkit/testkit.go:324 +0x8ae
  github.com/pingcap/tidb/testkit.(*TestKit).MustQueryWithContext()
      /home/wshwsh12/project/tidb/testkit/testkit.go:155 +0x154
  github.com/pingcap/tidb/testkit.(*TestKit).MustQuery()
      /home/wshwsh12/project/tidb/testkit/testkit.go:149 +0x107
  github.com/pingcap/tidb/executor/test/indexmergereadtest.TestProcessInfoRaceWithIndexScan()
      /home/wshwsh12/project/tidb/executor/test/indexmergereadtest/index_merge_reader_test.go:1163 +0x4b4
  github.com/pingcap/tidb/domain.(*Domain).LoadSysVarCacheLoop()
      /home/wshwsh12/project/tidb/domain/domain.go:1775 +0xa8
  github.com/pingcap/tidb/session.bootstrapSessionImpl()
      /home/wshwsh12/project/tidb/session/session.go:3357 +0x6e4
  github.com/pingcap/tidb/domain.(*Domain).GetSessionCache()
      /home/wshwsh12/project/tidb/domain/sysvar_cache.go:62 +0x5c
  github.com/pingcap/tidb/session.(*session).loadCommonGlobalVariablesIfNeeded()
      /home/wshwsh12/project/tidb/session/session.go:3721 +0x104
  github.com/pingcap/tidb/session.(*session).ExecuteStmt()
      /home/wshwsh12/project/tidb/session/session.go:2130 +0x145
  github.com/pingcap/tidb/session.(*session).ExecuteInternal()
      /home/wshwsh12/project/tidb/session/session.go:1666 +0x31b
  github.com/pingcap/tidb/domain.(*Domain).LoadPrivilegeLoop()
      /home/wshwsh12/project/tidb/domain/domain.go:1718 +0x130
  github.com/pingcap/tidb/session.bootstrapSessionImpl()
      /home/wshwsh12/project/tidb/session/session.go:3350 +0x687
  github.com/pingcap/tidb/session.BootstrapSession()
      /home/wshwsh12/project/tidb/session/session.go:3271 +0xb4
  github.com/pingcap/tidb/testkit.bootstrap()
      /home/wshwsh12/project/tidb/testkit/mockstore.go:218 +0x9b
  github.com/pingcap/tidb/testkit.CreateMockStoreAndDomain()
      /home/wshwsh12/project/tidb/testkit/mockstore.go:191 +0xe9
  github.com/pingcap/tidb/testkit.CreateMockStore()
      /home/wshwsh12/project/tidb/testkit/mockstore.go:66 +0x3b7
  github.com/pingcap/tidb/executor/test/indexmergereadtest.TestProcessInfoRaceWithIndexScan()
      /home/wshwsh12/project/tidb/executor/test/indexmergereadtest/index_merge_reader_test.go:1138 +0x58
  testing.tRunner()
      /home/wshwsh12/sdk/go1.20/src/testing/testing.go:1576 +0x216
  testing.(*T).Run.func1()
      /home/wshwsh12/sdk/go1.20/src/testing/testing.go:1629 +0x47

Previous read at 0x00c005259b30 by goroutine 16158:
  github.com/pingcap/tidb/util.GenLogFields()
      /home/wshwsh12/project/tidb/util/util.go:160 +0xf44
  github.com/pingcap/tidb/executor/test/indexmergereadtest.TestProcessInfoRaceWithIndexScan.func1()
      /home/wshwsh12/project/tidb/executor/test/indexmergereadtest/index_merge_reader_test.go:1159 +0xd4

4. What is your TiDB version? (Required)

master