Re: panic: vm_object_madvise: page 0xfffffe0413c58630 is fictitious

From: Andre Oppermann <andre_at_freebsd.org>
Date: Tue, 27 Nov 2012 19:43:24 +0100
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_at_bbb.ccc:/usr/obj/usr/src/head/sys/GENERIC  amd64
>>>>>
>>>>> #0  doadump (textdump=-2014022336) at pcpu.h:229
>>>>> #1  0xffffffff8033e2d2 in db_fncall (dummy1=<value optimized out>,
>>>>> dummy2=<value optimized out>,
>>>>>        dummy3=<value optimized out>, dummy4=<value optimized out>)
>>>>>        at /usr/src/head/sys/ddb/db_command.c:578
>>>>> #2  0xffffffff8033e074 in db_command (last_cmdp=<value optimized out>,
>>>>>        cmd_table=<value optimized out>, dopager=1) 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=<value optimized out>, code=0)
>>>>>        at /usr/src/head/sys/ddb/db_main.c:231
>>>>> #5  0xffffffff808b375e in kdb_trap (type=3, code=0, tf=<value
>>>>> optimized
>>>>> out>)
>>>>>        at /usr/src/head/sys/kern/subr_kdb.c:654
>>>>> #6  0xffffffff80bfc71a in trap (frame=0xffffff8487f478a0)
>>>>>        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=0xffffffff80e5e23b "panic",
>>>>> msg=<value optimized out>)
>>>>>        at cpufunc.h:63
>>>>> #9  0xffffffff8088086f in panic (fmt=<value optimized out>)
>>>>>        at /usr/src/head/sys/kern/kern_shutdown.c:628
>>>>> #10 0xffffffff80adea4a in vm_object_madvise (object=<value
>>>>> optimized out>,
>>>>>        pindex=<value optimized out>, end=8952, advise=<value
>>>>> optimized out>)
>>>>>        at /usr/src/head/sys/vm/vm_object.c:1101
>>>>> #11 0xffffffff80ad759a in vm_map_madvise (map=0xfffffe0018260188,
>>>>> start=<value optimized out>,
>>>>>        end=<value optimized out>, behav=5) at
>>>>> /usr/src/head/sys/vm/vm_map.c:2140
>>>>> #12 0xffffffff80adbd8d in sys_madvise (td=<value optimized out>,
>>>>> uap=<value optimized out>)
>>>>>        at /usr/src/head/sys/vm/vm_mmap.c:752
>>>>> #13 0xffffffff80bfd3a5 in amd64_syscall (td=0xfffffe0018230000,
>>>>> traced=0) 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=0xfffffe0018260188,
>> start=<value optimized out>,
>>      end=<value optimized out>, behav=5) at
>> /usr/src/head/sys/vm/vm_map.c:2140
>> 2140
>> vm_object_madvise(current->object.vm_object, pstart,
>> (kgdb) p *map
>> $1 = {header = {prev = 0xfffffe025631c438, next = 0xfffffe0248f119d8,
>> left = 0x0, right = 0x0,
>>      start = 4096, end = 140737488355328, avail_ssize = 0, adj_free =
>> 0, max_free = 0, object = {
>>        vm_object = 0x0, sub_map = 0x0}, offset = 0, eflags = 0,
>> protection = 0 '\0',
>>      max_protection = 0 '\0', inheritance = 0 '\0', read_ahead = 0
>> '\0', wired_count = 0,
>>      next_read = 0, cred = 0x0}, lock = {lock_object = {
>>        lo_name = 0xffffffff80e66905 "vm map (user)", lo_flags =
>> 36896768, lo_data = 0,
>>        lo_witness = 0xffffff80006c9700}, sx_lock = 17}, system_mtx =
>> {lock_object = {
>>        lo_name = 0xffffffff80e668d7 "vm map (system)", lo_flags =
>> 21168128, lo_data = 0,
>>        lo_witness = 0xffffff80006c9500}, mtx_lock = 4}, nentries = 32,
>> size = 64647168,
>>    timestamp = 52, needs_wakeup = 0 '\0', system_map = 0 '\0', flags =
>> 0 '\0',
>>    root = 0xfffffe02560a6258, pmap = 0xfffffe00182602b8, busy = 0}
>> (kgdb) p* map->pmap
>> $6 = {pm_mtx = {lock_object = {lo_name = 0xffffffff80e66934 "pmap",
>> lo_flags = 21168128,
>>        lo_data = 0, lo_witness = 0xffffff80006c9900}, mtx_lock = 4},
>> pm_pml4 = 0xfffffe0256458000,
>>    pm_pvchunk = {tqh_first = 0xfffffe0256142000, tqh_last =
>> 0xfffffe025644c008}, pm_active = {
>>      __bits = {1}}, pm_stats = {resident_count = 12683, wired_count = 0},
>>    pm_root = 0xfffffe041289e040}
>> (kgdb) p* map->root
>> $7 = {prev = 0xfffffe0018ed0708, next = 0xfffffe02560a6870, left =
>> 0xfffffe0018ed0708,
>>    right = 0xfffffe02560a6870, start = 34393292800, end = 34431041536,
>> avail_ssize = 0,
>>    adj_free = 140703057047552, max_free = 140703057047552, object = {
>>      vm_object = 0xfffffe0256484570, sub_map = 0xfffffe0256484570},
>> offset = 1810432, eflags = 0,
>>    protection = 3 '\003', max_protection = 7 '\a', inheritance = 1
>> '\001', read_ahead = 15 '\017',
>>    wired_count = 0, next_read = 0, cred = 0x0}
>>
>> (kgdb) p *current
>> $2 = {prev = 0xfffffe025631c438, next = 0xfffffe0248f119d8, left =
>> 0x0, right = 0x0, start = 4096,
>>    end = 140737488355328, avail_ssize = 0, adj_free = 0, max_free = 0,
>> object = {vm_object = 0x0,
>>      sub_map = 0x0}, offset = 0, eflags = 0, protection = 0 '\0',
>> max_protection = 0 '\0',
>>    inheritance = 0 '\0', read_ahead = 0 '\0', wired_count = 0,
>> next_read = 0, cred = 0x0}
>>
>> (kgdb) p *entry
>> $3 = {prev = 0xfffffe0018ed0708, next = 0xfffffe02560a6870, left =
>> 0xfffffe0018ed0708,
>>    right = 0xfffffe02560a6870, start = 34393292800, end = 34431041536,
>> avail_ssize = 0,
>>    adj_free = 140703057047552, max_free = 140703057047552, object = {
>>      vm_object = 0xfffffe0256484570, sub_map = 0xfffffe0256484570},
>> offset = 1810432, eflags = 0,
>>    protection = 3 '\003', max_protection = 7 '\a', inheritance = 1
>> '\001', read_ahead = 15 '\017',
>>    wired_count = 0, next_read = 0, cred = 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 = {pageq = {tqe_next = 0xfffffe04127fbcc8, tqe_prev = 0xfffffe0412658358}, listq = {
     tqe_next = 0xfffffe0413c586a8, tqe_prev = 0xfffffe0413c585c8}, left = 0xfffffe0413c585b8,
   right = 0xfffffe0413c586a8, object = 0xfffffe0256484570, pindex = 8868, phys_addr = 10744668160,
   md = {pv_list = {tqh_first = 0xfffffe025654d9a0, tqh_last = 0xfe025654d9a8}, pat_mode = 6},
   queue = 1 '\001', segind = 4 '\004', hold_count = 0, order = 13 '\r', pool = 0 '\0', cow = 0,
   wire_count = 0, aflags = 1 '\001', oflags = 0 '\0', flags = 65535, act_count = 5 '\005',
   busy = 0 '\0', valid = 255 'ÿ', dirty = 0 '\0'}

-- 
Andre
Received on Tue Nov 27 2012 - 17:41:56 UTC

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