Date: Fri, 12 Oct 2007 17:26:09 +0200 From: Kris Kennaway <kris@FreeBSD.org> To: Dan Nelson <dnelson@allantgroup.com> Cc: freebsd-current@freebsd.org, Ivan Voras <ivoras@freebsd.org> Subject: Re: Panic in arpresolve->rt_check? Message-ID: <470F9211.8010604@FreeBSD.org> In-Reply-To: <20071012143800.GA76105@dan.emsphone.com> References: <fc89en$fc2$1@sea.gmane.org> <20070912172752.GA13960@dan.emsphone.com> <fc9ce3$jps$1@sea.gmane.org> <200710101615.48760.jhb@freebsd.org> <20071012143800.GA76105@dan.emsphone.com>
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Dan Nelson wrote:
> In the last episode (Oct 10), John Baldwin said:
>> On Wednesday 12 September 2007 02:50:37 pm Ivan Voras wrote:
>>> Dan Nelson wrote:
>>>> The same panic was also reported for 6.2 via PR 107865 and PR
>>>> 112490. 112490 included a workaround patch (I haven't tried it;
>>>> just found it).
>>> The proposed patch in kern/112490 looks trivial but someone who
>>> knows more about net locking should check it out. Unfortunately it
>>> lacks context and I don't know the code in question to apply it
>>> safely on a production machine :(
>> I also get panics with what appears to be a double free of rt_gwroute
>> in rtexpunge(), so I think while this PR may help some with figuring
>> out the problem, I'm not sure it solves the root bug.
>>
>> Hmm, possibly try this patch:
>
> This makes the panics more frequent on my machine, actually :)
>
>> Index: route.c
>> ===================================================================
>> RCS file: /usr/cvs/src/sys/net/route.c,v
>> retrieving revision 1.120
>> diff -c -r1.120 route.c
>> *** route.c 11 Jun 2007 12:19:34 -0000 1.120
>> --- route.c 10 Oct 2007 20:12:54 -0000
>> ***************
>> *** 1314,1319 ****
>> --- 1314,1321 ----
>> return (ENETUNREACH);
>> }
>> RT_LOCK(rt0);
>> + if (rt0->rt_gwroute != NULL)
>> + RTFREE(rt0->rt_gwroute);
>> rt0->rt_gwroute = rt;
>> if (rt == NULL) {
>> RT_UNLOCK(rt0);
>
Since you can reproduce this frequently the best thing might be to
instrument all the route handling with KTR so that you can do
post-mortem and try to figure out where the double-free or missing
reference happened.
Kris
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