Re: [PATCH] firewire: fw-sbp2: don't retry login or reconnect after unplug

[Stefan Richter <stefanr@s5r6.in-berlin.de>]

I wrote:
> If a device is being unplugged while fw-sbp2 had a login or reconnect on
> schedule, it would take about half a minute to shut the fw_unit down:
> 
> Jan 27 18:34:54 stein firewire_sbp2: logged in to fw2.0 LUN 0000 (0 retries)
> <unplug>
> Jan 27 18:34:59 stein firewire_sbp2: sbp2_scsi_abort
> Jan 27 18:34:59 stein scsi 25:0:0:0: Device offlined - not ready after error recovery
> Jan 27 18:35:01 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:06 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:12 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:17 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:22 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:27 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:32 stein firewire_sbp2: orb reply timed out, rcode=0x11
> Jan 27 18:35:32 stein firewire_sbp2: failed to login to fw2.0 LUN 0000
> Jan 27 18:35:32 stein firewire_sbp2: released fw2.0
> 
> After this patch, typically only a few seconds spent in __scsi_add_device
> remain:
> 
> Jan 27 19:05:50 stein firewire_sbp2: logged in to fw2.0 LUN 0000 (0 retries)
> <unplug>
> Jan 27 19:05:56 stein firewire_sbp2: sbp2_scsi_abort
> Jan 27 19:05:56 stein scsi 33:0:0:0: Device offlined - not ready after error recovery
> Jan 27 19:05:56 stein firewire_sbp2: released fw2.0
> 
> The benefit of this is negligible on simple setups.  But on buses with
> several devices, we should avoid any unnecessary blockade of fw-sbp2's
> workqueue thread.

There is an error in the last sentences.  The time spent sleeping in
workqueue jobs is the same before and after.  What this patch only
avoids are a few wasted CPU cycles, irritating log messages, and
needlessly prolonged lifetime of a few driver objects.

However, less noise in the syslog may already be enough justification
for this patch.
-- 
Stefan Richter
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http://arcgraph.de/sr/