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Date:      Sat, 30 Nov 2002 15:43:05 +0300 (MSK)
From:      "Yan V.Batuto" <batuto@wgc.chem.pu.ru>
To:        FreeBSD-gnats-submit@FreeBSD.org
Subject:   kern/45889: Kernel trap 12 in sound/pcm code
Message-ID:  <20021130124305.88D951D80@yb3791.spb.edu>

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>Number:         45889
>Category:       kern
>Synopsis:       Kernel trap 12 in sound/pcm code
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Nov 30 14:50:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Yan V. Batuto
>Release:        FreeBSD 4.7-STABLE i386
>Organization:
St. Petersburg State University
>Environment:
System: FreeBSD 4.7-STABLE #0: Fri Nov 29 01:05:16 MSK 2002 i386
Motherboard: JetWay V333U (VIA KT333 with VT8235 south bridge)
pcm0: <VIA VT8235> port 0xe400-0xe4ff irq 5 at device 17.5 on pci0
	
>Description:
	
Kernel crashes usually during KDE initialization. It depends on
KDE configuration ("rm -rf ~/.kde && startx startkde" never
crashed yet, and AC'97 sound worked OK), and hw.snd.pcm0.vchans
setting. Kernel trap with hw.snd.pcm0.vchans=4 at least much
more probable than with vchans=0.

Trap occurs in dev/sound/pcm/feeder_rate.c:171
==== from gdb session ====
165                     alpha += info->srcinc;
166                     spos += (alpha >> 16) * 2;
167                     alpha &= 0xffff;
168
169             }
170             info->alpha = alpha & 0xffff;
171             info->buffer[0] = info->buffer[spos - hidelta];
172             info->buffer[1] = info->buffer[spos - hidelta + 1];

(kgdb) print spos-hidelta
$1 = -2
(kgdb) print info->buffer[spos-hidelta]
Cannot access memory at address 0xc0fe0ffc.
==== from gdb session ====

>How-To-Repeat:
	

>Fix:
As a ugly workaround try to 
sysctl -w hw.snd.pcm0.vchans=0
but I'm NOT sure it is sufficiently.
	


>Release-Note:
>Audit-Trail:
>Unformatted:

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