Date: Mon, 31 Jan 2011 08:52:48 -0800 From: Julian Elischer <julian@freebsd.org> To: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> Cc: freebsd-net@freebsd.org, Eugene Grosbein <egrosbein@rdtc.ru>, Mike Tancsa <mike@sentex.net> Subject: Re: panic: bufwrite: buffer is not busy??? Message-ID: <4D46E8E0.2030300@freebsd.org> In-Reply-To: <20110131122926.C39951@maildrop.int.zabbadoz.net> 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> <20110131122926.C39951@maildrop.int.zabbadoz.net>
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On 1/31/11 4:32 AM, Bjoern A. Zeeb wrote:
> 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.
slaps head... kassert is at work....
>
>
>> *** Error code 1
>> 1 error
>> *** Error code 2
>> 1 error
>> *** Error code 2
>> 1 error
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>
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