Date: Tue, 12 Aug 2008 08:42:52 +0200 From: Johan Kuuse <kuuse@redantigua.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-stable@freebsd.org Subject: Re: kernel panic Message-ID: <200808120842.52899.kuuse@redantigua.com> In-Reply-To: <200808111704.30604.jhb@freebsd.org> References: <200808110401.49953.kuuse@redantigua.com> <200808111704.30604.jhb@freebsd.org>
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On Monday 11 August 2008 23:04:30 John Baldwin wrote:
> On Sunday 10 August 2008 10:01:49 pm Johan Kuuse wrote:
> > Hi,
> >=20
> > I am a kgdb newbie, so please be patient.
> > I suspect (just based on the fact that this is the 4th time I edit text=
=20
> files on my NTFS partition through ntfs-3g, using Emacs, and getting freq=
uent=20
> I/O error messages inside Emacs, and then a kernel panic) that this is a=
=20
> ntfs-3g related problem.
> > If you ask me exactly how to reproduce it, I sorry, I can tell you exac=
tly=20
> (but see the kgdb output below).
> > Anyway, the kernel seems to panic at /usr/src/sys/kern/vfs_bio.c:1530
> >=20
> > Just a suggestion for a patch (without knowing the functionality=20
> of /usr/src/sys/kern/vfs_bio.c):
> >=20
> > The line where the kernel panics:
> > /usr/src/sys/kern/vfs_bio.c:
> > ----------------------------------
> > VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
> > ...
> > ----------------------------------
> >=20
> > Comparing to another file, which does error checking before calling=20
> VM_OBJECT_LOCK:
> > /usr/src/sys/kern/vfs_aio.c:
> > ----------------------------------
> > if (vp->v_object !=3D NULL) {
> > VM_OBJECT_LOCK(vp->v_object);
> > ...
> > ----------------------------------
> >=20
> > Perhaps the kernel panic could be avoided with the following patch?
> > /usr/src/sys/kern/vfs_bio.c (suggested patch):
> > ----------------------------------
> > if ((bp->b_bufobj !=3D NULL) && (bp->b_bufobj->bo_object !=3D NULL)) {
> > VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
> > ...
> > ----------------------------------
> >=20
> > Please let me know if you need more information.
> >=20
> > Regards,
> > Johan Kuuse
> >=20
> > -----------------------------------------------------------------------=
=2D-----------------------------------
> > kgdb kernel.debug /var/crash/vmcore.1=20
> > [GDB will not be able to debug user-mode threads: /usr/lib/libthread_db=
=2Eso:=20
> Undefined symbol "ps_pglobal_lookup"]
> > GNU gdb 6.1.1 [FreeBSD]
> > Copyright 2004 Free Software Foundation, Inc.
> > GDB is free software, covered by the GNU General Public License, and yo=
u are
> > welcome to change it and/or distribute copies of it under certain=20
> conditions.
> > Type "show copying" to see the conditions.
> > There is absolutely no warranty for GDB. Type "show warranty" for deta=
ils.
> > This GDB was configured as "i386-marcel-freebsd".
> >=20
> > Unread portion of the kernel message buffer:
> >=20
> >=20
> > Fatal trap 12: page fault while in kernel mode
> > cpuid =3D 0; apic id =3D 00
> > fault virtual address =3D 0x34
> > fault code =3D supervisor read, page not present
> > instruction pointer =3D 0x20:0xc07b6de4
> > stack pointer =3D 0x28:0xe79de7c8
> > frame pointer =3D 0x28:0xe79de7e8
> > code segment =3D base 0x0, limit 0xfffff, type 0x1b
> > =3D DPL 0, pres 1, def32 1, gran 1
> > processor eflags =3D interrupt enabled, resume, IOPL =3D 0
> > current process =3D 1214 (opera)
> > trap number =3D 12
> > panic: page fault
> > cpuid =3D 0
> > Uptime: 5h20m30s
> > Physical memory: 2035 MB
> > Dumping 218 MB: 203 187 171 155 139 123 107 91 75 59 43 27 11
> >=20
> > #0 doadump () at pcpu.h:195
> > 195 __asm __volatile("movl %%fs:0,%0" : "=3Dr" (td));
> > (kgdb) list *0xc07b6de4
> > 0xc07b6de4 is in vfs_vmio_release (/usr/src/sys/kern/vfs_bio.c:1530).
> > 1525 vfs_vmio_release(struct buf *bp)
> > 1526 {
> > 1527 int i;
> > 1528 vm_page_t m;
> > 1529
> > 1530 VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
> > 1531 vm_page_lock_queues();
> > 1532 for (i =3D 0; i < bp->b_npages; i++) {
> > 1533 m =3D bp->b_pages[i];
> > 1534 bp->b_pages[i] =3D NULL;
> > (kgdb) bt
> > #0 doadump () at pcpu.h:195
> > #1 0xc0754457 in boot (howto=3D260) at /usr/src/sys/kern/kern_shutdown=
=2Ec:409
> > #2 0xc0754719 in panic (fmt=3DVariable "fmt" is not available.
> > ) at /usr/src/sys/kern/kern_shutdown.c:563
> > #3 0xc0a4905c in trap_fatal (frame=3D0xe79de788, eva=3D52)=20
> at /usr/src/sys/i386/i386/trap.c:899
> > #4 0xc0a492e0 in trap_pfault (frame=3D0xe79de788, usermode=3D0, eva=3D=
52)=20
> at /usr/src/sys/i386/i386/trap.c:812
> > #5 0xc0a49c8c in trap (frame=3D0xe79de788)=20
> at /usr/src/sys/i386/i386/trap.c:490
> > #6 0xc0a2fc0b in calltrap () at /usr/src/sys/i386/i386/exception.s:139
> > #7 0xc07b6de4 in vfs_vmio_release (bp=3D0xd927e33c)=20
> at /usr/src/sys/kern/vfs_bio.c:1530
> > #8 0xc07b8a81 in getnewbuf (slpflag=3D0, slptimeo=3D0, size=3DVariable=
"size" is=20
> not available.
> > ) at /usr/src/sys/kern/vfs_bio.c:1847
> > #9 0xc07ba118 in getblk (vp=3D0xc8891bb0, blkno=3D0, size=3D2048, slpf=
lag=3D0,=20
> slptimeo=3D0, flags=3DVariable "flags" is not available.
> > ) at /usr/src/sys/kern/vfs_bio.c:2602
> > #10 0xc0932815 in ffs_balloc_ufs2 (vp=3D0xc8891bb0,=20
> startoffset=3DVariable "startoffset" is not available.
> > ) at /usr/src/sys/ufs/ffs/ffs_balloc.c:699
> > #11 0xc0952a85 in ffs_write (ap=3D0xe79debc4)=20
> at /usr/src/sys/ufs/ffs/ffs_vnops.c:720
> > #12 0xc0a5efc6 in VOP_WRITE_APV (vop=3D0xc0b93c60, a=3D0xe79debc4) at=20
> vnode_if.c:691
> > #13 0xc07dbf37 in vn_write (fp=3D0xc85f3168, uio=3D0xe79dec60,=20
> active_cred=3D0xc61c6300, flags=3D0, td=3D0xc583fc60) at vnode_if.h:373
> > #14 0xc07875e7 in dofilewrite (td=3D0xc583fc60, fd=3D17, fp=3D0xc85f316=
8,=20
> auio=3D0xe79dec60, offset=3D-1, flags=3D0) at file.h:254
> > #15 0xc07878c8 in kern_writev (td=3D0xc583fc60, fd=3D17, auio=3D0xe79de=
c60)=20
> at /usr/src/sys/kern/sys_generic.c:401
> > #16 0xc078793f in write (td=3D0xc583fc60, uap=3D0xe79decfc)=20
> at /usr/src/sys/kern/sys_generic.c:317
> > #17 0xc0a49635 in syscall (frame=3D0xe79ded38)=20
> at /usr/src/sys/i386/i386/trap.c:1035
> > #18 0xc0a2fc70 in Xint0x80_syscall ()=20
> at /usr/src/sys/i386/i386/exception.s:196
> > #19 0x00000033 in ?? ()
> > Previous frame inner to this frame (corrupt stack?)
>=20
> FYI, you got the panic in ffs/ufs, not fuse. I've seen this at work on 6=
=2Ex=20
> with NFS with no clues on what causes it. You can start by going to fram=
e 7=20
> and doing 'p *bp'.
>=20
Thanks for the hints.
See below for more debug output.
I recognize that the bp struct members b_data and b_kvabase both point to a=
chunk of memory containing the text of the Opera web page I was reading wh=
en the kernel crashed.
(This is indicated above: current process =3D 1214 (opera))
But what is most interesting is that b_bufobj =3D 0x0
Obviously, then trying to access bp->b_bufobj->bo_object will cause a crash.
So I think it would be a good idea to NULL-check the struct member before t=
rying to access it.
How should I proceed? Should I post this as a possible bug somewhere else, =
to another list?
Regards,
Johan Kuuse
(kgdb) up 7
#7 0xc07b6de4 in vfs_vmio_release (bp=3D0xd927e33c) at /usr/src/sys/kern/v=
fs_bio.c:1530
1530 VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
(kgdb) p *bp
$1 =3D {b_bufobj =3D 0x0, b_bcount =3D 4156, b_caller1 =3D 0x0,=20
b_data =3D 0xe03d9000 "TILL\201=C4MPNING\n- Formulera en fr\201=E5gest\20=
1=E4llning eller arbetsuppgift.\n- L\201=E4s texten noga och lyft ut det so=
m du anser \201=E4r ett queert l\201=E4ckage.\n Arbeta med mark\201=F6rer =
s\201=E5som genus, sexualitet och makt.\n- F"..., b_error =3D -1, b_iocmd =
=3D 2 '\002', b_ioflags =3D 0 '\0', b_iooffset =3D 0, b_resid =3D 1387, b_i=
odone =3D 0, b_blkno =3D 0, b_offset =3D 0, b_bobufs =3D {tqe_next =3D 0x0,=
tqe_prev =3D 0xc887da54}, b_left =3D 0x0,=20
b_right =3D 0x0, b_vflags =3D 0, b_freelist =3D {tqe_next =3D 0xd9363ea8,=
tqe_prev =3D 0xc0be18e8}, b_qindex =3D 0, b_flags =3D 536879648, b_xflags =
=3D 0 '\0', b_lock =3D {lk_object =3D {lo_name =3D 0xc0ada5df "bufwait",=20
lo_type =3D 0xc0ada5df "bufwait", lo_flags =3D 70844416, lo_witness_d=
ata =3D {lod_list =3D {stqe_next =3D 0x0}, lod_witness =3D 0x0}}, lk_interl=
ock =3D 0xc0bda1b8, lk_flags =3D 262144, lk_sharecount =3D 0, lk_waitcount =
=3D 0,=20
lk_exclusivecount =3D 1, lk_prio =3D 80, lk_timo =3D 0, lk_lockholder =
=3D 0xc583fc60, lk_newlock =3D 0x0}, b_bufsize =3D 4608, b_runningbufspace =
=3D 0,=20
b_kvabase =3D 0xe03d9000 "TILL\201=C4MPNING\n- Formulera en fr\201=E5gest=
\201=E4llning eller arbetsuppgift.\n- L\201=E4s texten noga och lyft ut det=
som du anser \201=E4r ett queert l\201=E4ckage.\n Arbeta med mark\201=F6r=
er s\201=E5som genus, sexualitet och makt.\n- F"..., b_kvasize =3D 65536, b=
_lblkno =3D 0, b_vp =3D 0x0, b_dirtyoff =3D 0, b_dirtyend =3D 1387, b_rcred=
=3D 0x0, b_wcred =3D 0xc61c6300, b_saveaddr =3D 0xe03d9000, b_pager =3D {p=
g_reqpage =3D 0}, b_cluster =3D {
cluster_head =3D {tqh_first =3D 0xd932fc48, tqh_last =3D 0xd9279a4c}, c=
luster_entry =3D {tqe_next =3D 0xd932fc48, tqe_prev =3D 0xd9279a4c}}, b_pag=
es =3D {0xc2b53bf8, 0xc2b72090, 0x0 <repeats 30 times>}, b_npages =3D 2, b_=
dep =3D {
lh_first =3D 0x0}, b_fsprivate1 =3D 0x0, b_fsprivate2 =3D 0x0, b_fspriv=
ate3 =3D 0x0, b_pin_count =3D 0}
(kgdb)
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