kernel panic
Johan Kuuse
kuuse at redantigua.com
Tue Aug 12 18:23:33 UTC 2008
> On Tuesday 12 August 2008 02:42:52 am Johan Kuuse wrote:
>> On Monday 11 August 2008 23:04:30 John Baldwin wrote:
>> > On Sunday 10 August 2008 10:01:49 pm Johan Kuuse wrote:
>> > > Hi,
>> > >
>> > > 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
>> >
>> > files on my NTFS partition through ntfs-3g, using Emacs, and getting
>> > frequent I/O error messages inside Emacs, and then a kernel panic) that
>> > this is a ntfs-3g related problem.
>> >
>> > > If you ask me exactly how to reproduce it, I sorry, I can tell you
>> > > exactly
>> >
>> > (but see the kgdb output below).
>> >
>> > > Anyway, the kernel seems to panic at /usr/src/sys/kern/vfs_bio.c:1530
>> > >
>> > > Just a suggestion for a patch (without knowing the functionality
>> >
>> > of /usr/src/sys/kern/vfs_bio.c):
>> > > The line where the kernel panics:
>> > > /usr/src/sys/kern/vfs_bio.c:
>> > > ----------------------------------
>> > > VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
>> > > ...
>> > > ----------------------------------
>> > >
>> > > Comparing to another file, which does error checking before calling
>> >
>> > VM_OBJECT_LOCK:
>> > > /usr/src/sys/kern/vfs_aio.c:
>> > > ----------------------------------
>> > > if (vp->v_object != NULL) {
>> > > VM_OBJECT_LOCK(vp->v_object);
>> > > ...
>> > > ----------------------------------
>> > >
>> > > Perhaps the kernel panic could be avoided with the following patch?
>> > > /usr/src/sys/kern/vfs_bio.c (suggested patch):
>> > > ----------------------------------
>> > > if ((bp->b_bufobj != NULL) && (bp->b_bufobj->bo_object != NULL)) {
>> > > VM_OBJECT_LOCK(bp->b_bufobj->bo_object);
>> > > ...
>> > > ----------------------------------
>> > >
>> > > Please let me know if you need more information.
>> > >
>> > > Regards,
>> > > Johan Kuuse
>> > >
>> > > -----------------------------------------------------------------------
>> > >------------------------------------ kgdb kernel.debug
>> > > /var/crash/vmcore.1
>> > > [GDB will not be able to debug user-mode threads:
>> > > /usr/lib/libthread_db.so:
>> >
>> > 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
>> > > 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 "i386-marcel-freebsd".
>> > >
>> > > Unread portion of the kernel message buffer:
>> > >
>> > >
>> > > Fatal trap 12: page fault while in kernel mode
>> > > cpuid = 0; apic id = 00
>> > > fault virtual address = 0x34
>> > > fault code = supervisor read, page not present
>> > > instruction pointer = 0x20:0xc07b6de4
>> > > stack pointer = 0x28:0xe79de7c8
>> > > frame pointer = 0x28:0xe79de7e8
>> > > code segment = base 0x0, limit 0xfffff, type 0x1b
>> > > = DPL 0, pres 1, def32 1, gran 1
>> > > processor eflags = interrupt enabled, resume, IOPL = 0
>> > > current process = 1214 (opera)
>> > > trap number = 12
>> > > panic: page fault
>> > > cpuid = 0
>> > > Uptime: 5h20m30s
>> > > Physical memory: 2035 MB
>> > > Dumping 218 MB: 203 187 171 155 139 123 107 91 75 59 43 27 11
>> > >
>> > > #0 doadump () at pcpu.h:195
>> > > 195 __asm __volatile("movl %%fs:0,%0" : "=r" (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 = 0; i < bp->b_npages; i++) {
>> > > 1533 m = bp->b_pages[i];
>> > > 1534 bp->b_pages[i] = NULL;
>> > > (kgdb) bt
>> > > #0 doadump () at pcpu.h:195
>> > > #1 0xc0754457 in boot (howto=260) at
>> > > /usr/src/sys/kern/kern_shutdown.c:409 #2 0xc0754719 in panic
>> > > (fmt=Variable "fmt" is not available.
>> > > ) at /usr/src/sys/kern/kern_shutdown.c:563
>> > > #3 0xc0a4905c in trap_fatal (frame=0xe79de788, eva=52)
>> >
>> > at /usr/src/sys/i386/i386/trap.c:899
>> >
>> > > #4 0xc0a492e0 in trap_pfault (frame=0xe79de788, usermode=0, eva=52)
>> >
>> > at /usr/src/sys/i386/i386/trap.c:812
>> >
>> > > #5 0xc0a49c8c in trap (frame=0xe79de788)
>> >
>> > 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=0xd927e33c)
>> >
>> > at /usr/src/sys/kern/vfs_bio.c:1530
>> >
>> > > #8 0xc07b8a81 in getnewbuf (slpflag=0, slptimeo=0, size=Variable
>> > > "size" is
>> >
>> > not available.
>> >
>> > > ) at /usr/src/sys/kern/vfs_bio.c:1847
>> > > #9 0xc07ba118 in getblk (vp=0xc8891bb0, blkno=0, size=2048, slpflag=0,
>> >
>> > slptimeo=0, flags=Variable "flags" is not available.
>> >
>> > > ) at /usr/src/sys/kern/vfs_bio.c:2602
>> > > #10 0xc0932815 in ffs_balloc_ufs2 (vp=0xc8891bb0,
>> >
>> > startoffset=Variable "startoffset" is not available.
>> >
>> > > ) at /usr/src/sys/ufs/ffs/ffs_balloc.c:699
>> > > #11 0xc0952a85 in ffs_write (ap=0xe79debc4)
>> >
>> > at /usr/src/sys/ufs/ffs/ffs_vnops.c:720
>> >
>> > > #12 0xc0a5efc6 in VOP_WRITE_APV (vop=0xc0b93c60, a=0xe79debc4) at
>> >
>> > vnode_if.c:691
>> >
>> > > #13 0xc07dbf37 in vn_write (fp=0xc85f3168, uio=0xe79dec60,
>> >
>> > active_cred=0xc61c6300, flags=0, td=0xc583fc60) at vnode_if.h:373
>> >
>> > > #14 0xc07875e7 in dofilewrite (td=0xc583fc60, fd=17, fp=0xc85f3168,
>> >
>> > auio=0xe79dec60, offset=-1, flags=0) at file.h:254
>> >
>> > > #15 0xc07878c8 in kern_writev (td=0xc583fc60, fd=17, auio=0xe79dec60)
>> >
>> > at /usr/src/sys/kern/sys_generic.c:401
>> >
>> > > #16 0xc078793f in write (td=0xc583fc60, uap=0xe79decfc)
>> >
>> > at /usr/src/sys/kern/sys_generic.c:317
>> >
>> > > #17 0xc0a49635 in syscall (frame=0xe79ded38)
>> >
>> > at /usr/src/sys/i386/i386/trap.c:1035
>> >
>> > > #18 0xc0a2fc70 in Xint0x80_syscall ()
>> >
>> > at /usr/src/sys/i386/i386/exception.s:196
>> >
>> > > #19 0x00000033 in ?? ()
>> > > Previous frame inner to this frame (corrupt stack?)
>> >
>> > FYI, you got the panic in ffs/ufs, not fuse. I've seen this at work on
>> > 6.x with NFS with no clues on what causes it. You can start by going to
>> > frame 7 and doing 'p *bp'.
>>
>> 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
>> when the kernel crashed. (This is indicated above: current process
>> = 1214 (opera))
>>
>> But what is most interesting is that b_bufobj = 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 trying to access it. How should I proceed? Should I post this as a
>> possible bug somewhere else, to another list?
>
> Unfortunately, it is a worse problem that b_bufobj is NULL. That means there
> is a bug elsewhere. I'll look at this some more.
>
> Hmm, can you reproduce this at all? If so, can you try the patch below.
> Hopefully it panics here which might help:
>
> Index: vfs_subr.c
> ===================================================================
> --- vfs_subr.c (revision 181629)
> +++ vfs_subr.c (working copy)
> @@ -1546,6 +1546,9 @@
> CTR3(KTR_BUF, "brelvp(%p) vp %p flags %X", bp, bp->b_vp, bp->b_flags);
> KASSERT(bp->b_vp != NULL, ("brelvp: NULL"));
>
> + if (bp->flags & B_VMIO)
> + panic("brelvp of B_VMIO buffer");
> +
> /*
> * Delete from old vnode list, if on one.
> */
>
> --
> John Baldwin
>
Sorry, at the moment I don't know how to reproduce the crash.
I mentioned ntfs-ng/fuse as I got the impression that they caused a heavy load
on my box, but in the end, it was Opera which caused the crash (also causing a
heavy load, however).
What I can do is to apply your patch and play around with CPU-consuming apps to
try if I can reproduce the crash during heavy load.
Currently I'm running 7.-0-RELEASE.
Do you recommend me to upgrade to STABLE before applying the patch?
Regards,
Johan Kuuse
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