Messages in this thread |  | | Date | Mon, 19 Dec 2022 15:55:01 +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 15:28, Jason Yan wrote: >>> + if (test_bit(SAS_DEV_GONE, &dev->state) && dev_is_sata(dev)) >>> + sas_ata_device_link_abort(dev, false); >> >> Firstly, I think that there is a bug in sas_ata_device_link_abort() -> >> ata_link_abort() code in that the host lock in not grabbed, as the >> comment in ata_port_abort() mentions. Having said that, libsas had >> already some dodgy host locking usage - specifically dropping the lock >> for the queuing path (that's something else to be fixed up ... I think > > Taking big locks in queuing path is not a good idea. This will bring > down performance.
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.
Thanks, John
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