kernel panic
John Baldwin
jhb at freebsd.org
Tue Aug 12 13:08:33 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
More information about the freebsd-stable
mailing list