Re: panic: vm_object_madvise: page 0xfffffe0413c58630 is fictiti


On 27.11.2012 19:27, Alan Cox wrote:
> On 11/27/2012 12:08, Andre Oppermann wrote:
>> On 27.11.2012 17:42, Alan Cox wrote:
>>> On 11/27/2012 09:06, Konstantin Belousov wrote:
>>>> On Tue, Nov 27, 2012 at 12:26:44PM +0100, Andre Oppermann wrote:
>>>>> FreeBSD bbb.ccc 10.0-CURRENT FreeBSD 10.0-CURRENT #0:
>>>>> Fri Nov 23 17:00:40 CET 2012
>>>>> aaa@bbb.ccc:/usr/obj/usr/src/head/sys/GENERIC  amd64
>>>>>
>>>>> #0  doadump (textdump=3D-2014022336) at pcpu.h:229
>>>>> #1  0xffffffff8033e2d2 in db_fncall (dummy1=3D<value optimized out>,
>>>>> dummy2=3D<value optimized out>,
>>>>>        dummy3=3D<value optimized out>, dummy4=3D<value optimized out>)
>>>>>        at /usr/src/head/sys/ddb/db_command.c:578
>>>>> #2  0xffffffff8033e074 in db_command (last_cmdp=3D<value optimized ou=
t>,
>>>>>        cmd_table=3D<value optimized out>, dopager=3D1) at
>>>>> /usr/src/head/sys/ddb/db_command.c:449
>>>>> #3  0xffffffff8033dd62 in db_command_loop () at
>>>>> /usr/src/head/sys/ddb/db_command.c:502
>>>>> #4  0xffffffff80340690 in db_trap (type=3D<value optimized out>, code=
=3D0)
>>>>>        at /usr/src/head/sys/ddb/db_main.c:231
>>>>> #5  0xffffffff808b375e in kdb_trap (type=3D3, code=3D0, tf=3D<value
>>>>> optimized
>>>>> out>)
>>>>>        at /usr/src/head/sys/kern/subr_kdb.c:654
>>>>> #6  0xffffffff80bfc71a in trap (frame=3D0xffffff8487f478a0)
>>>>>        at /usr/src/head/sys/amd64/amd64/trap.c:579
>>>>> #7  0xffffffff80be65b2 in calltrap () at /tmp/exception-3nQ6Cf.s:179
>>>>> #8  0xffffffff808b2f5e in kdb_enter (why=3D0xffffffff80e5e23b "panic",
>>>>> msg=3D<value optimized out>)
>>>>>        at cpufunc.h:63
>>>>> #9  0xffffffff8088086f in panic (fmt=3D<value optimized out>)
>>>>>        at /usr/src/head/sys/kern/kern_shutdown.c:628
>>>>> #10 0xffffffff80adea4a in vm_object_madvise (object=3D<value
>>>>> optimized out>,
>>>>>        pindex=3D<value optimized out>, end=3D8952, advise=3D<value
>>>>> optimized out>)
>>>>>        at /usr/src/head/sys/vm/vm_object.c:1101
>>>>> #11 0xffffffff80ad759a in vm_map_madvise (map=3D0xfffffe0018260188,
>>>>> start=3D<value optimized out>,
>>>>>        end=3D<value optimized out>, behav=3D5) at
>>>>> /usr/src/head/sys/vm/vm_map.c:2140
>>>>> #12 0xffffffff80adbd8d in sys_madvise (td=3D<value optimized out>,
>>>>> uap=3D<value optimized out>)
>>>>>        at /usr/src/head/sys/vm/vm_mmap.c:752
>>>>> #13 0xffffffff80bfd3a5 in amd64_syscall (td=3D0xfffffe0018230000,
>>>>> traced=3D0) at subr_syscall.c:135
>>>>> #14 0xffffffff80be689b in Xfast_syscall () at
>>>>> /tmp/exception-3nQ6Cf.s:329
>>>>> #15 0x00000000016f3bfa in ?? ()
>>>> I think this is an omission in the check for the object types. BTW,
>>>> this
>>>> pattern already repeats in several places, I thought about adding
>>>> either
>>>> new pager method, like boolean_t vm_pager_is_pageable(), or just a flag
>>>> fields to the struct vm_pager to classify the vm objects.
>>>
>>>
>>> A fictitious page should always have a non-zero wire count.  In fact, it
>>> should always be one and never change.  (See vm_page_unwire().)  In
>>> vm_object_madvise(), there is a check against the page's wire count that
>>> precedes the KASSERT().  This check should prevent the KASSERT() from
>>> being reached for the various device-backed object types.  So, something
>>> else has gone wrong here, or rather something has gone wrong elsewhere
>>> that caused the KASSERT() failure here.
>>>
>>> Andre, can we see the contents of the offending struct vm_page and also
>>> the struct vm_object to which the offending page belongs to?  Also, are
>>> you running a kernel with any experimental zero-copy send support?
>>
>> No experimental zero-copy support, or anything else, just a stock
>> GENERIC kernel.
>>
>> (kgdb) frame 11
>> #11 0xffffffff80ad759a in vm_map_madvise (map=3D0xfffffe0018260188,
>> start=3D<value optimized out>,
>>      end=3D<value optimized out>, behav=3D5) at
>> /usr/src/head/sys/vm/vm_map.c:2140
>> 2140
>> vm_object_madvise(current->object.vm_object, pstart,
>> (kgdb) p *map
>> $1 =3D {header =3D {prev =3D 0xfffffe025631c438, next =3D 0xfffffe0248f1=
19d8,
>> left =3D 0x0, right =3D 0x0,
>>      start =3D 4096, end =3D 140737488355328, avail_ssize =3D 0, adj_fre=
e =3D
>> 0, max_free =3D 0, object =3D {
>>        vm_object =3D 0x0, sub_map =3D 0x0}, offset =3D 0, eflags =3D 0,
>> protection =3D 0 '\0',
>>      max_protection =3D 0 '\0', inheritance =3D 0 '\0', read_ahead =3D 0
>> '\0', wired_count =3D 0,
>>      next_read =3D 0, cred =3D 0x0}, lock =3D {lock_object =3D {
>>        lo_name =3D 0xffffffff80e66905 "vm map (user)", lo_flags =3D
>> 36896768, lo_data =3D 0,
>>        lo_witness =3D 0xffffff80006c9700}, sx_lock =3D 17}, system_mtx =
=3D
>> {lock_object =3D {
>>        lo_name =3D 0xffffffff80e668d7 "vm map (system)", lo_flags =3D
>> 21168128, lo_data =3D 0,
>>        lo_witness =3D 0xffffff80006c9500}, mtx_lock =3D 4}, nentries =3D=
 32,
>> size =3D 64647168,
>>    timestamp =3D 52, needs_wakeup =3D 0 '\0', system_map =3D 0 '\0', fla=
gs =3D
>> 0 '\0',
>>    root =3D 0xfffffe02560a6258, pmap =3D 0xfffffe00182602b8, busy =3D 0}
>> (kgdb) p* map->pmap
>> $6 =3D {pm_mtx =3D {lock_object =3D {lo_name =3D 0xffffffff80e66934 "pma=
p",
>> lo_flags =3D 21168128,
>>        lo_data =3D 0, lo_witness =3D 0xffffff80006c9900}, mtx_lock =3D 4=
},
>> pm_pml4 =3D 0xfffffe0256458000,
>>    pm_pvchunk =3D {tqh_first =3D 0xfffffe0256142000, tqh_last =3D
>> 0xfffffe025644c008}, pm_active =3D {
>>      __bits =3D {1}}, pm_stats =3D {resident_count =3D 12683, wired_coun=
t =3D 0},
>>    pm_root =3D 0xfffffe041289e040}
>> (kgdb) p* map->root
>> $7 =3D {prev =3D 0xfffffe0018ed0708, next =3D 0xfffffe02560a6870, left =
=3D
>> 0xfffffe0018ed0708,
>>    right =3D 0xfffffe02560a6870, start =3D 34393292800, end =3D 34431041=
536,
>> avail_ssize =3D 0,
>>    adj_free =3D 140703057047552, max_free =3D 140703057047552, object =
=3D {
>>      vm_object =3D 0xfffffe0256484570, sub_map =3D 0xfffffe0256484570},
>> offset =3D 1810432, eflags =3D 0,
>>    protection =3D 3 '\003', max_protection =3D 7 '\a', inheritance =3D 1
>> '\001', read_ahead =3D 15 '\017',
>>    wired_count =3D 0, next_read =3D 0, cred =3D 0x0}
>>
>> (kgdb) p *current
>> $2 =3D {prev =3D 0xfffffe025631c438, next =3D 0xfffffe0248f119d8, left =
=3D
>> 0x0, right =3D 0x0, start =3D 4096,
>>    end =3D 140737488355328, avail_ssize =3D 0, adj_free =3D 0, max_free =
=3D 0,
>> object =3D {vm_object =3D 0x0,
>>      sub_map =3D 0x0}, offset =3D 0, eflags =3D 0, protection =3D 0 '\0',
>> max_protection =3D 0 '\0',
>>    inheritance =3D 0 '\0', read_ahead =3D 0 '\0', wired_count =3D 0,
>> next_read =3D 0, cred =3D 0x0}
>>
>> (kgdb) p *entry
>> $3 =3D {prev =3D 0xfffffe0018ed0708, next =3D 0xfffffe02560a6870, left =
=3D
>> 0xfffffe0018ed0708,
>>    right =3D 0xfffffe02560a6870, start =3D 34393292800, end =3D 34431041=
536,
>> avail_ssize =3D 0,
>>    adj_free =3D 140703057047552, max_free =3D 140703057047552, object =
=3D {
>>      vm_object =3D 0xfffffe0256484570, sub_map =3D 0xfffffe0256484570},
>> offset =3D 1810432, eflags =3D 0,
>>    protection =3D 3 '\003', max_protection =3D 7 '\a', inheritance =3D 1
>> '\001', read_ahead =3D 15 '\017',
>>    wired_count =3D 0, next_read =3D 0, cred =3D 0x0}
>
>
> The following tells us that this is an OBJT_DEFAULT (i.e., anonymous)
> memory object.  Such objects should never contain fictitious pages.  Can
> you please print the contents of the offending struct vm_page using the
> address from the panic message?

(kgdb) p (struct vm_page)*0xfffffe0413c58630
$12 =3D {pageq =3D {tqe_next =3D 0xfffffe04127fbcc8, tqe_prev =3D 0xfffffe0=
412658358}, listq =3D {
     tqe_next =3D 0xfffffe0413c586a8, tqe_prev =3D 0xfffffe0413c585c8}, lef=
t =3D 0xfffffe0413c585b8,
   right =3D 0xfffffe0413c586a8, object =3D 0xfffffe0256484570, pindex =3D =
8868, phys_addr =3D 10744668160,
   md =3D {pv_list =3D {tqh_first =3D 0xfffffe025654d9a0, tqh_last =3D 0xfe=
025654d9a8}, pat_mode =3D 6},
   queue =3D 1 '\001', segind =3D 4 '\004', hold_count =3D 0, order =3D 13 =
'\r', pool =3D 0 '\0', cow =3D 0,
   wire_count =3D 0, aflags =3D 1 '\001', oflags =3D 0 '\0', flags =3D 6553=
5, act_count =3D 5 '\005',
   busy =3D 0 '\0', valid =3D 255 '=FF', dirty =3D 0 '\0'}

-- =

Andre

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