Re: DANGER WILL ROBINSON! SERIOUS problem with current 5.4-PRERELEASE

From: Karl Denninger (karl_at_denninger.net)
Date: 03/30/05

  • Next message: Matthew N. Dodd: "Re: DANGER WILL ROBINSON! SERIOUS problem with current 5.4-PRERELEASE" 
    Date: Tue, 29 Mar 2005 23:08:30 -0600
To: "Matthew N. Dodd" <mdodd@freebsd.org>

    On Tue, Mar 29, 2005 at 11:40:48PM -0500, Matthew N. Dodd wrote:
    > On Tue, 29 Mar 2005, Karl Denninger wrote:
    > > 1.42: When resubmitting a timed out request, reset donecount.
    > > 1.41: Reset timeout when we are back from interrupt.
    > > 1.40: Correct logical error, result was that retries wasn't always made but
    > > failure reported instead.
    > > 1.39: Do not retry on requests that have lost their device during reinit.
    > >
    > > This change is EXTREMELY DANGEROUS.
    > >
    > > This change needs to be backed out immediately until it can be determined
    > > why a requeued request destabilizes the system.
    >
    > The changes in question are very small. Could you attempt to isolate
    > which one is the cause?
    >
    > Thanks.

    Pretty sure its the requeue (e.g. 1.40 and 1.42); I attempted to put this
    patch in the system back before it was MFC'd (when it orginally showed up in
    -HEAD) and it failed in exactly the same way. The first time it created a
    LOT of head-scratching ("how come my serial board has suddenly gone deaf?!")
    and it wasn't until it got to where the console wouldn't respond that the
    light went on and I said "oh, so THAT's what that patch really does!" :->

    That got backed out FAST :-)

    I believe the previous version of that file in -STABLE was 1.38 - that has
    the 'errors don't actually get retried' problem that results in immediate
    detaches - the reason for the update was that I noted the commit and
    figured that the problem from my last attempt with including this had
    either been fixed or I had missed some dependancy in my earlier attempt.

    I have an open PR on the underlying problem (SATA drives on a number of
    common configurations returning false errors and detaching when part of a
    geom mirror) which I've marked as "serious". Its at
    http://www.freebsd.org/cgi/query-pr.cgi?pr=77643

    There is a comment attached to the PR from another user who has duplicated
    the underlying problem.

    Note that back on 3/2/05 I attempted to apply the 1.42 version of this file
    to -STABLE and got the same failure, and added that fact to the PR. I also
    reported it here. It appears that both reports were either missed or ignored
    and this change was committed to -RELENG_5.

    I'm not sure if I can cobble up a test machine with the right configuration
    of hardware to go through each of the above changes in turn to see if I can
    isolate which of the three it is, but I'll give it a shot over the next
    couple of days. I'm 1 SATA disk short of what I need to do this in my
    sandbox.

    If I do not trigger the requeue all appears to be fine.

    This is one that IMHO has to either be found and fixed or backed out for the
    impending -RELEASE. 

    --
-- 
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