On 09/11/2016 20:35, Dan Williams wrote:
On Wed, Nov 9, 2016 at 11:09 AM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
On Wed, Nov 9, 2016 at 9:36 AM, John Garry <john.garry@xxxxxxxxxx> wrote:
On 09/11/2016 12:28, John Garry wrote:
On 03/11/2016 14:58, John Garry wrote:
The following patch introduces an annoying WARN
when a device is removed from the SAS topology:
[SCSI] libsas: prevent domain rediscovery competing with ata error
handling
Are there any views on this patch? I would have thought that the parties
who use the drivers based on libsas would be interested in fixing this
bug.
I should have added the before and after logs earlier, so the issue is
illustrated. Now attached. When a 24-port expander is unplugged we get >6k
lines of WARN on the console, lasting >30 seconds. Not nice.
I might be mistaken, but this patch seems functionally identical to
this attempt:
http://marc.info/?l=linux-scsi&m=143459794823595&w=2
Hi Dan,
They're not the same. I don't see how your solution properly deals with
remote sas_port deletion.
When we unplug a device connected to an expander, can't the sas_port be
deleted twice, in sas_unregister_devs_sas_addr() from domain
revalidation and also now in sas_destruct_devices()? I think that this
gives a NULL dereference.
And we still get the WARN as the sas_port has still been deleted before
the device.
In my solution, we should always delete the sas_port after the attached
device.
i.e. it moves the port destruction to the workqueue and still suffers
from the flutter problem:
http://marc.info/?l=linux-scsi&m=143801026028006&w=2
http://marc.info/?l=linux-scsi&m=143801971131073&w=2
Perhaps we instead need to quiet this warning?
http://marc.info/?l=linux-scsi&m=143802229932175&w=2
I have not seen the flutter issue. I am just trying to solve the
horrible WARN dump.
However I do understand that there may be a issue related to how we
queue the events; there was a recent attempt to fix this, but it came to
nothing:
https://www.spinics.net/lists/linux-scsi/msg99991.html
Cheers,
John
Alternatively we need a mechanism to cancel in-flight port shutdown
requests when we start re-attaching devices before queued port
destruction events have run.
.
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