# [Know Issue]关于 TiDB 日志无报错偶发性异常重启

## Key Words

重启,Panic,invalid memory address,data race,kv client

## Description

TiDB 进程在没有负载的情况下发生重启，tidb 日志无报错，system 日志未发现异常，查看 stderr 日志有 panic 信息。

## Root Cause

该问题是由于 TiDB Server 的 KV Client 中连接存在数据争用 BUG[(详情见 Issue)](https://github.com/pingcap/tidb/issues/33773),导致 TiDB Server panic [(对应 TiDB 修复 PR)](https://github.com/pingcap/tidb/pull/39706)，随后被 service 服务重启。

## Diagnostic Steps

查看 TiDB 对应组件的 error log，观察是否存在下述类似堆栈信息，即：```invalid memory address or nil pointer dereference``` 及 ```tikv/client.(*RPCClient).SendRequest```。

```go
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x220 pc=0x1aca454]

goroutine 176997991 [running]:
google.golang.org/grpc.(*ClientConn).GetState(...)
        /root/go/pkg/mod/google.golang.org/grpc@v1.27.1/clientconn.go:521
github.com/pingcap/tidb/store/tikv/client.(*RPCClient).SendRequest(0x4000f1a680, 0x3774230, 0x4000d90ec0, 0x40066c1248, 0x12, 0x402edbe000, 0x4a817c800, 0x0, 0x0, 0x0)
        /var/lib/docker/jenkins/workspace/build-common@4/go/src/github.com/pingcap/tidb/store/tikv/client/client.go:376 +0x1f4
github.com/pingcap/tidb/store/tikv/client.reqCollapse.SendRequest(0x3753408, 0x4000f1a680, 0x3774230, 0x4000d90ec0, 0x40066c1248, 0x12, 0x402edbe000, 0x4a817c800, 0xf8, 0x30d9100, ...)
        /var/lib/docker/jenkins/workspace/build-common@4/go/src/github.com/pingcap/tidb/store/tikv/client/client_collapse.go:53 +0xd4
github.com/pingcap/tidb/store/tikv.(*KVStore).updateSafeTS.func1(0x3753430, 0x4000e8a8f0, 0x4000546300, 0x3774230, 0x4000d90ec0, 0x4049984030, 0x355372f6, 0x40066c1248, 0x12)
        /var/lib/docker/jenkins/workspace/build-common@4/go/src/github.com/pingcap/tidb/store/tikv/kv.go:414 +0x12c
created by github.com/pingcap/tidb/store/tikv.(*KVStore).updateSafeTS
        /var/lib/docker/jenkins/workspace/build-common@4/go/src/github.com/pingcap/tidb/store/tikv/kv.go:412 +0xf8
```

## Resolution

升级至 v5.1.5, v5.2.1, v5.3.2, v5.4.1, v6.1.0

## Affected Versions

TiDB Version < v5.1.5, v5.2.1, v5.3.2, v5.4.1, v6.1.0