lightning may panic when user cancel #41235
Description
Bug Report
Please answer these questions before submitting your issue. Thanks!
1. Minimal reproduce step (Required)
use failpoint to reproduce pingcap/tiflow#8209
panic: send on closed channel
goroutine 345 [running]:
github.com/pingcap/tidb/br/pkg/membuf.(*Pool).release(0xc0006a88d0, {0x7fa9d430b010, 0x100000, 0x100000})
/home/lance/Projects/tidb/br/pkg/membuf/buffer.go:112 +0x72
github.com/pingcap/tidb/br/pkg/membuf.(*Buffer).Destroy(0xc001718050)
/home/lance/Projects/tidb/br/pkg/membuf/buffer.go:177 +0x185
github.com/pingcap/tidb/br/pkg/lightning/backend/local.(*Writer).Close(0xc000a494d0, {0x521b7e8?, 0xc000d60d70?})
/home/lance/Projects/tidb/br/pkg/lightning/backend/local/engine.go:1201 +0x1c3
github.com/pingcap/tidb/br/pkg/lightning/backend.(*LocalEngineWriter).Close(...)
/home/lance/Projects/tidb/br/pkg/lightning/backend/backend.go:431
github.com/pingcap/tidb/br/pkg/lightning/restore.(*TableRestore).restoreEngine.func3(0x0?, 0xc000dff3a0)
/home/lance/Projects/tidb/br/pkg/lightning/restore/table_restore.go:595 +0x24e
created by github.com/pingcap/tidb/br/pkg/lightning/restore.(*TableRestore).restoreEngine
/home/lance/Projects/tidb/br/pkg/lightning/restore/table_restore.go:582 +0x117b
2. What did you expect to see? (Required)
no panic