From owner-freebsd-stable  Wed May 29 13:52:44 2002
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To: Mark Ibell <marki@econz.co.nz>
Cc: freebsd-stable@freebsd.org
Subject: Re: Daily kernel panics on 4.6-RC system 
In-Reply-To: Your message of "Wed, 29 May 2002 14:29:00 +1200."
             <008b01c206b8$981dbcb0$166e10ac@MARKI> 
Date: Wed, 29 May 2002 21:52:32 +0100
From: Ian Dowse <iedowse@maths.tcd.ie>
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In message <008b01c206b8$981dbcb0$166e10ac@MARKI>, Mark Ibell writes:
>We have had trouble with our Dell PowerEdge 1400 server since day one and it
>has now got to the point where it kernel panics once or twice a day.  The
>1400 currently runs 4.6-RC but we have had a similar problem with
>4.3-RELEASE & 4.5-RELEASE, although the problem has definitely got a lot
>worse since upgrading to 4.6-RC.  Perhaps someone can make sense of the
>following crash dump info.

>Fatal trap 12: page fault while in kernel mode
>fault virtual address   = 0x50
>fault code              = supervisor read, page not present

>#6  0xc024100b in tcp_output (tp=0xde1ef7c0) at
>/usr/src/sys/netinet/tcp_output.c:942

This crash "shouldn't happen"; the code is trying to read tp->rcv_nxt
in the line

	if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))

but somehow the non-NULL `tp' argument has become NULL during the
execution of the function. In the assembly output here, `tp' is
kept in one register throughout the whole tcp_output() function,
so it must be getting corrupted by one of the functions called by
tcp_output(). Are you using any unusual compiler optimisations in
/etc/make.conf? There are known issues with using -O2 or greater
that would certainly explain these crashes.

It would also be worth trying different hardware to determine if
this is a software or hardware issue.

Ian

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