Date: Tue, 30 Jan 2001 03:07:58 -0800 From: Julian Elischer <julian@elischer.org> To: Harti Brandt <brandt@fokus.gmd.de> Cc: julian@freebsd.org, freebsd-net@freebsd.org, archie@freebsd.org Subject: Re: netgraph: problem in ng_base Message-ID: <3A76A08E.8B5B3896@elischer.org> References: <Pine.BSF.4.21.0101301113380.390-100000@beagle.fokus.gmd.de>
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Harti Brandt wrote:
>
> Hi,
>
> Just a bit more information: I just tried to run my PDP-11 simulator
> while having loaded ng_ether from the previous tests. The simulator uses
> the if_tap interface to emulate an ethernet interface to the PDP. Suddenly
> the system crashed while doing an ifconfig. The crash occured in
> ng_ether_output, because the node pointer in the interface structure was
> NULL. It checked the sources of if_tap and ng_ether, but could not find,
> how this was caused. So I tried to repeat the crash, but no luck. The
> trace from the crashdump shows:
[...]
> Frame #11 was ng_ether_output in ddb.
>
> But while trying to repeat the crash I suddenly discovered the following
> in /var/log/messages:
>
> Jan 30 11:05:56 beagle /boot/kernel/kernel: Accessing freed node node: ID [3]: type 'ether', 0 hooks, flags 0x9, 0 refs, :
> Jan 30 11:05:56 beagle /boot/kernel/kernel: Last active @ /usr/src/sys/modules/netgraph/netgraph/../../../netgraph/ng_base.c, line 2436
> Jan 30 11:05:56 beagle /boot/kernel/kernel: problem discovered at file /usr/src/sys/modules/netgraph/ether/../../../netgraph/ng_ether.c, line 341
> Jan 30 11:05:56 beagle /boot/kernel/kernel: Accessing freed node node: ID [3]: type 'ether', 0 hooks, flags 0x9, 0 refs, :
> Jan 30 11:05:56 beagle /boot/kernel/kernel: Last active @ /usr/src/sys/modules/netgraph/ether/../../../netgraph/ng_ether.c, line 341
> Jan 30 11:05:56 beagle /boot/kernel/kernel: problem discovered at file /usr/src/sys/modules/netgraph/ether/../../../netgraph/ng_ether.c, line 344
> Jan 30 11:05:56 beagle /boot/kernel/kernel: Accessing freed node node: ID [3]: type 'ether', 0 hooks, flags 0x9, 0 refs, :
> Jan 30 11:05:56 beagle /boot/kernel/kernel: Last active @ /usr/src/sys/modules/netgraph/ether/../../../netgraph/ng_ether.c, line 344
> Jan 30 11:05:56 beagle /boot/kernel/kernel: problem discovered at file /usr/src/sys/modules/netgraph/ether/../../../netgraph/ng_ether.c, line 345
>
> That looks exactly like my problem, so I assume it is not the sscop code.
>
I think we'll find it's a problem with queueing and dequeueng packets....
I'm looking there now....
(queued packets are supposed to hold a reference to the node they are queued on,
and that reference is supposed to be released when the packet is dequeued, but I
have a suspicion that I screwed it and am releasing it twice..
Do you use NG_SEND_DATA_ONLY() in the atm node??
> harti
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__--_|\ Julian Elischer
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( OZ ) World tour 2000-2001
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