Messages in this thread | | | Date | Tue, 20 Dec 2022 08:43:31 +0000 | Subject | Re: [PATCH V2] scsi: libsas: Directly kick-off EH when ATA device fell off | From | John Garry <> |
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On 19/12/2022 23:00, Damien Le Moal wrote: >> But it is expected that ata_qc_issue() should be called with that the >> host lock grabbed (and keep it). >> >> I think that the reason libsas drops the lock is because some LLDD >> queuecommand CBs calls task_done() in some error paths. If we kept the >> lock held, then we could have a deadlock, for example: >> >> sas_ata_qc_issue (has lock) -> lldd_execute_task() = >> pm8001_queue_command() -> task_done() = sas_ata_task_done() -> grab host >> lock => deadlock. > That should be easily solvable using a workqueue for doing task_done(), no ? >
I don't see why we cannot just return an error code directly from the lldd_execute_task CB always - we end up calling scsi_done() directly then. But I am suspicious why it is not already done this way.
Looking at the code history, this fiddling with the ap->lock actually looks related to commit 312d3e56119a4bc5c36a96818f87f650c069ddc2 ("[SCSI] libsas: remove ata_port.lock management duties from lldds"). I will check that further.
Thanks, John
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