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Date:      Fri, 30 Aug 2002 13:19:38 +0200 (CEST)
From:      Pawel Jakub Dawidek <nick@garage.freebsd.pl>
To:        FreeBSD-gnats-submit@FreeBSD.org
Subject:   kern/42198: Kernel panics or system hangs up with big SC_HISTORY_SIZE and VESA.
Message-ID:  <20020830111938.597EB3ABD40@milla.ask33.net>
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>Number:         42198
>Category:       kern
>Synopsis:       Kernel panics or system hangs up with big SC_HISTORY_SIZE and VESA.
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Aug 30 04:20:02 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Pawel Jakub Dawidek
>Release:        FreeBSD 4.6-STABLE i386
>Organization:
Private
>Environment:
System: FreeBSD milla.ask33.net 4.6-STABLE FreeBSD 4.6-STABLE #9: Wed Jul 31 21:18:46 CEST 2002 root@milla.ask33.net:/usr/obj/usr/src/sys/MILLA i386


>Description:
	There are some serious problems with big values of SC_HISTORY_SIZE
	and VESA video driver. Kernel panics when we are trying to load
	vesa.ko module and SC_HISTORY_SIZE is big or system hangs up when
	SC_HISTORY_SIZE is big and VESA is compiled in kernel.

>How-To-Repeat:
	There are two ways:
	1. Compile kernel with big (for example 5000) SC_HISTORY_SZIE and
	   without VESA. Then reboot machine and do

		# kldload vesa

	   Kernel sould panic.

	2. Compile kernel with big (for example 5000) SC_HISTORY_SIZE and
	   with VESA support, then reboot machine and:

		# vidcontrol 132x60

	   then:

		# cat <some_big_file>

	   few times. When history buffer fills up system will hangs up.

	But there is a chance that those are two diffrent bugs.
>Fix:
	I don't know exactly. Backtrace after panic shows lncintr_sc()
	function from /sys/i386/isa/if_lnc.c.
	But I don't think secound problem (with system hangs up) is there.
	Problem could be here (from /sys/dev/syscons/schistory.c):

	#define	SC_MAX_HISTORY_SIZE	(1000 * MAXCONS * NSC)

	NSC is as I suppose number of chars per line. But where it is defined?
	I can't grep it. And there is a chance that this is to less for
	132 chars per line, because maybe somewhere buffer size is counted
	as number_of_lines * x_console_size and we got overflow.

	But I could be wrong:)
>Release-Note:
>Audit-Trail:
>Unformatted:

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