window post scheduler notifs channel closed

[hxg8202]

Lotus' api ChainNotify is called in WindowPoStScheduler.Run, sometimes it keeps blocking, causing WindowPoSt to not run normally!
anybody help me?
log:
2021-09-25T04:20:50.932+0900 WARN storageminer storage/wdpost_sched.go:123 window post scheduler notifs channel closed
2021-09-25T04:20:50.932+0900 WARN events events/events.go:106 listenHeadChanges quit
2021-09-25T04:20:50.932+0900 ERROR miner miner/miner.go:232 failed to get best mining candidate: handler: websocket connection closed
2021-09-25T04:20:50.932+0900 WARN events events/events.go:106 listenHeadChanges quit
2021-09-25T04:20:50.933+0900 WARN sectors storage-sealing/fsm.go:616 sector 78893 got error event sealing.SectorChainPreCommitFailed: handler: websocket connection closed
2021-09-25T04:20:50.933+0900 WARN sectors storage-sealing/fsm.go:616 sector 78986 got error event sealing.SectorChainPreCommitFailed: handler: websocket connection closed
2021-09-25T04:20:50.933+0900 WARN sectors storage-sealing/fsm.go:616 sector 78863 got error event sealing.SectorChainPreCommitFailed: handler: websocket connection closed
2021-09-25T04:20:50.933+0900 WARN sectors storage-sealing/fsm.go:616 sector 78769 got error event sealing.SectorChainPreCommitFailed: handler: websocket connection closed
2021-09-25T04:20:50.933+0900 WARN sectors storage-sealing/fsm.go:616 sector 78947 got error event sealing.SectorChainPreCommitFailed: handler: websocket connection closed

#6883