kernel panic

[Johan Kuuse]

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"]
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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?)
(kgdb)
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