ddl/ddl.go: Recv from chan `task.err` may block forever when send is skipped · pingcap/tidb#26763

(4 commenti) (0 reazioni) (1 assegnatario)Go (6186 fork)batch import

help wantedsig/sql-infratype/enhancement

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Descrizione

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

We found this bug through a WIP Fuzzing project by system-pclub, PSU

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

In ddl_worker.go, limitDDLJobs() calls addBatchDDLJobs() on L272 if selecting the first case, which in turn calls sending operation task.err <-err on L311. https://github.com/pingcap/tidb/blob/fa71a0e46d427e8a7450a2dce27f8c0d4c02a45c/ddl/ddl_worker.go#L258-L275 https://github.com/pingcap/tidb/blob/fa71a0e46d427e8a7450a2dce27f8c0d4c02a45c/ddl/ddl_worker.go#L310-L311 Then in ddl.go, doDDLJob() calls receiving operation err := <-task.err on L540 https://github.com/pingcap/tidb/blob/fa71a0e46d427e8a7450a2dce27f8c0d4c02a45c/ddl/ddl.go#L534-L540

3. What did you see instead (Required)

If the select in limitDDLJobs() chooses the second case, the sending operation in function addBatchDDLJobs() will be skipped. Thus the receiving operation in doDDLJob() will block forever.

4. What is your TiDB version? (Required)

branch: master commit: 7e6690df8e8d5474b1872edbd279bb1b3c510ee5

Guida contributor

Direzione di ricerca: Analizza la logica di invio/ricezione dei canali in ddl worker.go e ddl.go per assicurarti che l'invio venga sempre eseguito prima della ricezione, oppure gestisci il caso in cui l'invio viene saltato dall'istruzione select.
Tech stack: go
Dominio: backend
Tipo issue: Bug
Difficoltà: 2
Tempo stimato: 1-3 ore
Stato attività: Attiva
Chiarezza: Chiara
Prerequisiti: Go
Adatta ai principianti: 60