Date: Mon, 31 Jan 2011 12:32:15 +0000 (UTC) From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: Eugene Grosbein <egrosbein@rdtc.ru> Cc: freebsd-net@freebsd.org, Mike Tancsa <mike@sentex.net> Subject: Re: panic: bufwrite: buffer is not busy??? Message-ID: <20110131122926.C39951@maildrop.int.zabbadoz.net> In-Reply-To: <4D4685A0.6040400@rdtc.ru> References: <4D3011DB.9050900@frasunek.com> <4D30458D.30007@sentex.net> <4D309983.70709@rdtc.ru> <201101141437.55421.jhb@freebsd.org> <4D46575A.802@rdtc.ru> <4D4670C2.4050500@freebsd.org> <4D4685A0.6040400@rdtc.ru>
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On Mon, 31 Jan 2011, Eugene Grosbein wrote:
> On 31.01.2011 14:20, Julian Elischer wrote:
>
>>> # gdb kernel
>>> GNU gdb 6.1.1 [FreeBSD]
>>> Copyright 2004 Free Software Foundation, Inc.
>>> GDB is free software, covered by the GNU General Public License, and you are
>>> welcome to change it and/or distribute copies of it under certain conditions.
>>> Type "show copying" to see the conditions.
>>> There is absolutely no warranty for GDB. Type "show warranty" for details.
>>> This GDB was configured as "amd64-marcel-freebsd"...
>>> (gdb) l *0xffffffff803c1315
>>> 0xffffffff803c1315 is in ng_address_hook (/home/src/sys/netgraph/ng_base.c:3504).
>>> 3499 * Quick sanity check..
>>> 3500 * Since a hook holds a reference on it's node, once we know
>>> 3501 * that the peer is still connected (even if invalid,) we know
>>> 3502 * that the peer node is present, though maybe invalid.
>>> 3503 */
>>> 3504 if ((hook == NULL) ||
>>> 3505 NG_HOOK_NOT_VALID(hook) ||
>>> 3506 NG_HOOK_NOT_VALID(peer = NG_HOOK_PEER(hook)) ||
>>> 3507 NG_NODE_NOT_VALID(peernode = NG_PEER_NODE(hook))) {
>>> 3508 NG_FREE_ITEM(item);
>>
>>
>> replace with:
which is essentially what I had suggested in the formerly mentioned PR
already (just remove the first printf macro).
>> 3504 if ((hook == NULL) ||
>> 3505 NG_HOOK_NOT_VALID(hook) ||
>> ((peer = NG_HOOK_PEER(hook)) == NULL) ||
>> 3506 NG_HOOK_NOT_VALID(peer) ||
>> ((peernode = NG_PEER_NODE(hook)) == NULL) ||
>> 3507 NG_NODE_NOT_VALID(peernode)) {
>> if (peer)
>> kassert((peernode != NULL), ("peer node NULL wile peer hook exists"));
>> 3508 NG_FREE_ITEM(item);
>>
The problem is that it will not help to fix the race; if you go
up in the same file you'll find another similar one of these checks
with a scary rev 1.1. (I think) comment (that you, Julian, should know
very well;-)
The solution that this needs is: proper locking.
> It does not compile:
>
> /home/src/sys/netgraph/ng_base.c: In function 'ng_address_hook':
> /home/src/sys/netgraph/ng_base.c:3511: warning: implicit declaration of function 'kassert'
> /home/src/sys/netgraph/ng_base.c:3511: warning: nested extern declaration of 'kassert'
yeah KASSERT is upper case.
> *** Error code 1
> 1 error
> *** Error code 2
> 1 error
> *** Error code 2
> 1 error
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--
Bjoern A. Zeeb You have to have visions!
<ks> Going to jail sucks -- <bz> All my daemons like it!
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/jails.html
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