Re: [9fans] dns

[Kenji Arisawa <arisawa@ar.aichi-u.ac.jp>]

Hello cinap,

I got a one. I hope this a helpful.


ar% cat broken/1345779846.41356
name=dns
/proc/41356/text:386 plan 9 executable
/sys/lib/acid/port
/sys/lib/acid/386
acid: abort()+0x0 /sys/src/libc/9sys/abort.c:6
ppanic(p=0x3975c,fmt=0x394ec)+0x146 /sys/src/libc/port/malloc.c:166
	pv=0x3e820
	msg=0x3f804
	v=0xdfffc800
	n=0x2c
D2B(p=0x3975c,v=0x497f8)+0x5a /sys/src/libc/port/pool.c:968
	a=0x497f0
poolfreel(v=0x497f8,p=0x3975c)+0x20 /sys/src/libc/port/pool.c:1192
	ab=0x3e820
poolfree(p=0x3975c,v=0x497f8)+0x41 /sys/src/libc/port/pool.c:1327
free(v=0x49800)+0x23 /sys/src/libc/port/malloc.c:250
mydnsquery(qp=0x88cf0,udppkt=0xc76f0,len=0x2a,medium=0x1)+0x185 /sys/src/cmd/ndb/dnresolve.c:1032
	rv=0xc
	domain=0x49800
	net=0x74656e2f
	conndir=0x74656e2f
	nci=0x52b59
	belen=0x6e2f000f
xmitquery(qp=0x88cf0,depth=0x1,medium=0x1,inns=0x1,obuf=0xc76f0,len=0x2a)+0x227 /sys/src/cmd/ndb/dnresolve.c:1114
	p=0xc7950
	j=0x1
	n=0x0
	buf=0x1b59c4c3
tcpquery(qp=0x88cf0,waitms=0x63f,obuf=0xc76f0,ibuf=0xa7530,depth=0x1,inns=0x1,len=0x2a,req=0x1d85,mp=0xdfffc9b4)+0xea /sys/src/cmd/ndb/dnresolve.c:1353
	rv=0x0
	endms=0x56ba1ef1
queryns(qp=0x88cf0,obuf=0xc76f0,depth=0x1,inns=0x1,waitms=0x63f,ibuf=0xa7530)+0x4d3 /sys/src/cmd/ndb/dnresolve.c:1428
	req=0xa9961d85
	len=0x2a
	dest=0xc7950
	p=0xc7c30
	ndest=0x1
	endms=0x56ba1dcc
	replywaits=0x0
	buf=0x9dfa996
	m=0x1d85
	srcip=0xdfffca18
	rv=0x9dfa996
udpquery(mntpt=0x3f0e0,qp=0x88cf0,patient=0x0,depth=0x1,inns=0x1)+0x1b7 /sys/src/cmd/ndb/dnresolve.c:1578
	ibuf=0xa7530
	obuf=0xc76f0
	fd=0xb
	msg=0x6faa
	pcntprob=0x3c
	reqtm=0x1f40
	wait=0x63f
	rv=0x87710
netquery(depth=0x1,qp=0x88cf0)+0x2b5 /sys/src/cmd/ndb/dnresolve.c:1660
	rv=0x0
	dp=0x6d460
	qlp=0x6d4fc
	lock=0x1
	buf=0x3975c
	triedin=0x0
	inname=0x1
netqueryns(qp=0x88cf0,nsrp=0x876b0,depth=0x1)+0x1e /sys/src/cmd/ndb/dnresolve.c:338
	rv=0x88ce8
issuequery(class=0x1,qp=0x88cf0,depth=0x0,name=0xdfffce13,recurse=0x0)+0x50 /sys/src/cmd/ndb/dnresolve.c:359
	nsrp=0x876b0
	cp=0x88cf0
	dbnsrp=0x8558
	rp=0x0
dnresolve1(name=0xdfffce13,type=0xf,class=0x1,req=0xdfffcdd8,depth=0x0,recurse=0x0)+0x25c /sys/src/cmd/ndb/dnresolve.c:505
	dp=0x6d460
	rp=0x0
	qp=0x88cf0
dnresolve(status=0xdfffcce0,depth=0x0,rooted=0x0,name=0xdfffce13,class=0x1,type=0xf,req=0xdfffcdd8,cn=0x0,recurse=0x0)+0xa8 /sys/src/cmd/ndb/dnresolve.c:198
	procname=0x9cb50
	rp=0x0
	drp=0x71a98
	nrp=0x9cb40
	nname=0x48
	dp=0xdfffcca8
	loops=0x9cb90
lookupqueryold(p=0xdfffce13,mf=0xbac50,req=0xdfffcdd8,rooted=0x0,job=0xba810,errbuf=0xdfffcd0c,wantsav=0x0)+0x70 /sys/src/cmd/ndb/dns.c:864
	status=0x0
	rp=0x9cb48
rwrite(job=0xba810,mf=0xbac50,req=0xdfffcdd8)+0x2be /sys/src/cmd/ndb/dns.c:838
	err=0x0
	cnt=0x1b
	send=0x0
	errbuf=0x0
	atype=0xdfffce2c
io()+0x39e /sys/src/cmd/ndb/dns.c:532
	req=0x1
	mdata=0x32
	n=0x32
	job=0xba810
	mf=0xbac50
main(argv=0xdfffefb0,argc=0x0)+0x32c /sys/src/cmd/ndb/dns.c:267
	ext=0x0
	_argc=0x72
	_args=0xdfffefc7
	servefile=0x642f7323
	dir=0x0
	kid=0x0
_main+0x31 /sys/src/libc/386/main9.s:16
acid: 
echo kill > /proc/41356/ctl
ar% 

Kenji Arisawa

On 2012/08/21, at 20:27, cinap_lenrek@gmx.de wrote:

> nothing wrong with diffing the changes and see if theres a clue, but
> to solve this one really needs to find the underlying cause no matter
> what. changes can just hide bugs or make them more or less likely to
> appear. can anyone provide at least a stacktrace or process snapshot
> of the crashed dns processes? from that you try to build a theory of
> what might be going wrong by thinking really really hard... (the
> thinking should be directly proportional to the time it takes to
> reproduce the bug) and then you work on how to prove that theory.
> just changing stuff without knowing what exactly was the problem with
> the old code is sometimes tempting, but wrong and dangerous.
> 
> --
> cinap
>