panic: bufwrite: buffer is not busy???

[Julian Elischer]

On 1/30/11 10:31 PM, Eugene Grosbein wrote:
> On 15.01.2011 01:37, John Baldwin wrote:
>> On Friday, January 14, 2011 1:44:19 pm Eugene Grosbein wrote:
>>> On 14.01.2011 18:46, Mike Tancsa wrote:
>>>
>>>>> I'm using mpd 5.5 on three PPPoE routers, each servicing about 300 PPPoE
>>>>> concurrent sessions. Routers are based on Intel SR1630GP hardware platforms and
>>>>> runs FreeBSD 7.3-RELEASE.
>>>>>
>>>>> I'm experiencing stability issues related to Netgraph. None of above routers can
>>>>> survive more than 20-30 days of uptime under typical load. There are different
>>>>> flavors of kernel panics, but all are somehow related to netgraph. Typical
>>>>> backtraces follow
>>>> I also have stability issues on RELENG_8.
>>>>
>>>> http://www.freebsd.org/cgi/query-pr.cgi?pr=153497
>>> And for one of my servers (8.2-PRERELEASE/amd64 with 4GB RAM) I just cannot obtain crashdump,
>>> it cannot finish to write it. For example, it happened an hour ago:
>>>
>>> Fatal trap 12: page fault while in kernel mode
>>> cpuid = 2; apic id = 04
>>> fault virtual address   = 0x200000040
>>> fault code              = supervisor read data, page not present
>>> instruction pointer     = 0x20:0xffffffff803cc979
>> Assuming your kernel is built with debug symbols (which is the default), one
>> thing you can do to aid in debugging is this:
>>
>> gdb /boot/kernel/kernel
>> (gdb) l *0xffffffff803cc979
>>
>> Where the 0xfff<blah>  bit is the part of the 'instruction pointer' value
>> above after the colon (:) and then send the output of that in your e-mail to
>> the list.  This allows us to the source line at which the fault occurred.
>>
> Yesterday I've got another kernel panic of this kind with RELENG_8 updated 20 January
> and it still could not finish writing of crashdump:
>
> Fatal trap 12: page fault while in kernel mode
> cpuid = 1; apic id = 02
> fault virtual address   = 0x200000030
> fault code              = supervisor read data, page not present
> instruction pointer     = 0x20:0xffffffff803c1315
> stack pointer           = 0x28:0xffffff8000130780
> frame pointer           = 0x28:0xffffff80001307a0
> code segment            = base 0x0, limit 0xfffff, type 0x1b
>                          = DPL 0, pres 1, long 1, def32 0, gran 1
> processor eflags        = interrupt enabled, resume, IOPL = 0
> current process         = 12 (irq259: em1:rx 0)
> trap number             = 12
> panic: page fault
> cpuid = 1
> Uptime: 19h41m8s
> Dumping 4087 MB (3 chunks)
>    chunk 0: 1MB (150 pages) ... ok
>    chunk 1: 3575MB (915088 pages) 3559 3543panic: bufwrite: buffer is not busy???
> cpuid = 1
> Uptime: 19h41m9s
> Automatic reboot in 15 seconds - press a key on the console to abort
>
> This time I have all debug symbols handy:
>
>
> # 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:

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);


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