Dan Williams wrote:
On 2/17/2011 3:36 PM, David Milburn wrote:
Dan Williams wrote:
Commit 56dd2c06 "libsas: Don't issue commands to devices that have been
hot-removed" edited Darrick's original patch to remove setting 'gone' in
the sas_deform_port() path because that prevented scsi sync cache
commands from being issued when the driver was unloaded. However, this
allows true device gone notifications (as signaled port phy events) to
trigger sync cache commands to devices that are known to be unreachable.
Teach libsas which sas_deform_port() invocations are likely device gone
events.
This patch also introduces sas_device_gone() which hopefully allows
subtle/tricky locking to be dropped from lldd drivers, like the
following in mvsas which is broken if the ata path is ever converted to
call lldd_execute_task() with irqs enabled:
flags_libsas = 0;
[...]
spin_unlock_irqrestore(dev->sata_dev.ap->lock, flags_libsas);
spin_unlock_irqrestore(&mvi->lock, flags);
t->task_done(t);
spin_lock_irqsave(&mvi->lock, flags);
spin_lock_irqsave(dev->sata_dev.ap->lock, flags_libsas);
Cc: Darrick J. Wong<djwong@xxxxxxxxxx>
Cc: Haipao Fan<haipao.fan@xxxxxxxxx>
Cc: Maciej Trela<maciej.trela@xxxxxxxxx>
Cc: David Milburn<dmilburn@xxxxxxxxxx>
Signed-off-by: Dan Williams<dan.j.williams@xxxxxxxxx>
---
The sas_device_gone() change could be split into its own patch for
bisection
purposes, let me know if you want me to resubmit. This is being
driven by a
lockdep error in isci as it calls task->done() from lldd_execute_task()
when it finds lldd_dev == NULL for the ata domain_device.
Dan,
So, you are seeing sas_ata_task_done() trying to get the ata_port lock,
but it has already been taken earlier in the code path?
ata_scsi_queuecmd (spin_lock_irqsave(ap->lock, irq_flags)
__ata_scsi_queuecmd
ata_scsi_translate
ata_qc_issue
sas_ata_qc_issue
isci_task_execute_task
isci_task_complete_for_upper_layer
sas_ata_task_done
(spin_lock_irqsave(dev->sata_dev.ap->lock, flags)
Exactly.
sas_device_gone() should prevent an lldd from ever attempting an i/o to
a missing sata device (one that has been notified via lldd_dev_gone).
Although, I have only had time to verify the simple unplug case and
sync-cache commands at driver unload. We'll still need to handle
missing ssp devices, but there are no lldd-external locking concerns in
that path.
Dan,
One other question, should sas_device_gone() be sync'ing with sata io
thru ata port lock instead of the Scsi_Host lock?
Looking at sas_queuecommand, the host_lock is released and the ata
port lock is taken before calling ata_sas_queuecmd, and ata port lock is
held
down the __ata_scsi_queuecmd path.
Should sas_device_gone get the ap->lock from the domain_device->
sata_dev to better sync against sata io?
Thanks,
David
--
Dan
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