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Date:      Sat, 07 Oct 2000 22:58:20 -0400 (EDT)
From:      Bosko Milekic <bmilekic@dsuper.net>
To:        gibbs@freebsd.org
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: latest ahc panic, more data ...
Message-ID:  <Pine.BSF.4.21.0010072233400.285-100000@jehovah.technokratis.com>
In-Reply-To: <Pine.BSF.4.21.0010072208460.9375-100000@hub.org>

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  I've just been hit by one such problem on bootup. This is -current as of
  today, so I suspect it's the commits that went in the past two days.

  Basically, I tracked it down just enough to know that the problem is
  happening during a call to ahc_print_path() in aic7xxx.c, specifically
  for me, this happens during bootup in ahc_handle_scsiint() right after
  the second call to ahc_abort_scbs().

  ahc_print_path() is called like this:

  	ahc_print_path(ahc, scb);

	(why both ahc and scb are being passed, I have no idea, since
	ahc_print_path only actually makes use of scb).

  For the unaware, ahc_print_path() seems to only wrap a call to
  xpt_print_path() to which it passes scb->io_ctx->ccb_h.path as an
  argument, and in this case, scb->io_ctx happens to be NULL, so during its
  pass, a NULL pointer gets dereferenced and the page fault happens.

  The NULLing out of this is coming somewhere in ahc_handle_scsiint(),
  because some prior ahc_print_path()s (with the same arguments) are
  succeeding.

  I have not tried backing out the changes from the past two days and
  trying again, but this was not happening a week ago.

  So what's going on here?

On Sat, 7 Oct 2000, Marc G. Fournier wrote:

> 
> okay, have been watching the conversation going on in the committers list,
> and am watching for any new commits that seem appropriate, but figure
> adding a little bit of extra info as I come up with it might help?
> 
> latest reboot had a bit more info then the last, and started with:
> 
> ahc0:A:1: ahc_intr - referenced scb not valid during seqint 0x73 scb(147)
> ach0: WARNING no command for scb 147 (cmdcmplt)
> QOUTPOS=132
> 
> Marc G. Fournier                               scrappy@hub.org
> Systems Administrator @ hub.org                    
> scrappy@{postgresql|isc}.org                       ICQ#7615664



  Bosko Milekic
  bmilekic@technokratis.com




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