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
