Re: cdrom buffer i/o error on heavily loaded system

On Thu, 28 Jun 2007, Alex Chiang wrote:

> Hello,
> 
> I have a Teac DV-28E-N cdrom, and I've been seeing some buffer
> I/O errors on a heavily loaded system (uptime indicates system
> load of 390 or so).
> 
> Turning on USB debugging for usbcore and mass storage indicates
> that something is timing out (hanging?), which makes the SCSI
> mid-layer issue an abort, and then a bus reset.
> 
> This problem occurs on 2.6.16 but seems to go away in 2.6.18.
> Upgrading to 2.6.18 isn't an option.
> 
> I've been poking through the git logs to try and figure out
> what's changed between 2.6.16 and 2.6.18, and found some patches
> that looked promising:
> 
>   usb-storage-get-rid-of-timer.patch
>   http://marc.info/?l=linux-usb-devel&m=115092809714473&w=2
> 
>   usb-core-get-rid-of-timer.patch
>   http://marc.info/?l=linux-usb-devel&m=115938791628537&w=2
> 
> But applying those didn't seem to help.
> 
> If someone could point me in the right direction, either with an
> explanation of why my device is timing out, further
> instrumentation I could add to my kernel to figure out what's
> going on, or a patch that magically solves this problem ;), I'd
> really appreciate it. 

The errors shown in your logs are not problems in the usb-storage
driver, so whatever fixed them in 2.6.18 was a change made somewhere
else.  Probably in the USB host controller driver, but maybe in the USB
scatter-gather library or somewhere else entirely.

The log showed that all the requested data had been transferred but
nevertheless the request didn't complete.

Alan Stern


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