why does udev set timeout for all SCSI devices?

why does udev set timeout for all SCSI devices?

[Tejun Heo]

Hello, Kay.

As the $SUBJ says, why does udev set timeout for all SCSI devices?
It's the following two rules.

50-udev-default.rules:SUBSYSTEM=="scsi", KERNEL=="[0-9]*:[0-9]*",
ACTION=="add", ATTR{type}=="0|7|14", ATTR{timeout}="60"
50-udev-default.rules:SUBSYSTEM=="scsi", KERNEL=="[0-9]*:[0-9]*",
ACTION=="add", ATTR{type}=="1", ATTR{timeout}="900"

The appropriate default timeout differs depending on the transport and
the type of the attached device, so the above two rules harm more than
help.  The affect of the above two rules weren't visible for some
reason but with recent block layer timeout update, they actually work
and cause problems.

Thanks.

-- 
tejun

Re: why does udev set timeout for all SCSI devices?

[Kay Sievers]

On Thu, Oct 30, 2008 at 03:55, Tejun Heo <tj@kernel.org> wrote:
> As the $SUBJ says, why does udev set timeout for all SCSI devices?
> It's the following two rules.
>
> 50-udev-default.rules:SUBSYSTEM=="scsi", KERNEL=="[0-9]*:[0-9]*",
> ACTION=="add", ATTR{type}=="0|7|14", ATTR{timeout}="60"
> 50-udev-default.rules:SUBSYSTEM=="scsi", KERNEL=="[0-9]*:[0-9]*",
> ACTION=="add", ATTR{type}=="1", ATTR{timeout}="900"
>
> The appropriate default timeout differs depending on the transport and
> the type of the attached device, so the above two rules harm more than
> help.  The affect of the above two rules weren't visible for some
> reason but with recent block layer timeout update, they actually work
> and cause problems.

It's in there for years, I can not even dig out, where it is coming
from. I just removed it from the default rules.

Thanks,
Kay