Re: [BK PATCH] USB changes for 2.5.34

Matthew Dharm
2002-09-10T02:02:29Z

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Linus, normally I would agree with you on this, but...

(1) We can't always handle it. The current code implements a heuristic,
which is not always correct. When it gets it wrong....

(2) show_trace() was proving ineffective in bringing the bad commands to
light so they might be fixed

(3) Given that we think we've fixed all of these bad initiators, the BUG()
really is something that should never happen.

Matt

On Mon, Sep 09, 2002 at 05:17:40PM -0700, Linus Torvalds wrote:
>
> Greg, please don't do this
>
> > ChangeSet@1.614, 2002-09-05 08:33:20-07:00, greg@kroah.com
> > USB: storage driver: replace show_trace() with BUG()
>
> that BUG() thing is _way_ out of line, and has killed a few of my machines
> several times for no good reason. It actively hurts debuggability, because
> the machine is totally dead after it, and the whole and ONLY point of
> BUG() messages is to help debugging and make it clear that we can't handle
> something.
>
> In this case, we _can_ handle it, and we're much better off with a machine
> that works and that you can look up the messages with than killing it.
>
> Rule of thumb: BUG() is only good for something that never happens and
> that we really have no other option for (ie state is so corrupt that
> continuing is deadly).
>
> Linus
>
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--
Matthew Dharm Home: mdharm-usb@one-eyed-alien.net
Maintainer, Linux USB Mass Storage Driver

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