panic: System call lstat returning with 1 locks held

[Scot Hetzel]

On 1/30/08, Attilio Rao <attilio at freebsd.org> wrote:
> 2008/1/30, Yar Tikhiy <yar at comp.chem.msu.su>:
> > On Tue, Jan 29, 2008 at 11:11:13PM +0100, Attilio Rao wrote:
> > >
> > > I'm committing my WITNESS patch now to perforce so that other people
> > > can hopefully stress-test it before to be committed.
> >
> > Do you think that that patch is applicable in my case?  I.e., shall
> > I use it to get more debug info on my panics?
> >
> > If so, where is the patched file in the depot?
>
> Sorry but I had to delay the operation so far.
> In the end, a suitable patch is located here:
> http://www.freebsd.org/~attilio/witness_lockmgr.diff
>
> I tried it and it alredy reported 4 LORs just when booting the kernel :)
> So I would expect reasonably LOR cascades with this patch.
>
> If you all 3 (Scot, Yar and Doug) could try and test it I would
> appreciate a lot.
>
Reading back to Doug's and Yar's messages regarding the NTFS
filesystem, I noticed that I am also mounting NTFS filesystems at boot
time.  I disabled the mounting of the NTFS filesystems.  When 'cd
/usr/ports ; find . -print' or '/usr/local/etc/cvsup/update.sh' is
run, the panic doesn't occur.

But when I mount the NTFS filesystem, and rerun the above commands,
they cause the lstat panic.  Even though these commands are not
touching the NTFS filesystems.

Also mounting/unmounting a NTFS filesystem will cause a panic.

I applied the above patch to sources that were checked out about 2 hrs
ago.  Rebuilt/installed kernel and rebooted.

If I don't mount a NTFS filesystem then the kernel doesn't panic when
the above commands are run.

But when the NTFS filesystem is mounted, the following lock order
reversal occurs:

lock order reversal:
 1st 0xffffff0023285288 pseudofs (pseudofs) @ kern/vfs_subr.c:2061
 2nd 0xffffff00232f2ca0 vfslock (vfslock) @ kern/vfs_subr.c:364
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
witness_checkorder() at witness_checkorder+0x606
_lockmgr() at _lockmgr+0x4cb
vfs_busy() at vfs_busy+0xdf
vfs_donmount() at vfs_donmount+0x9aa
nmount() at nmount+0xa4
syscall() at syscall+0x1ce
Xfast_syscall() at Xfast_syscall+0xab
--- syscall (378, FreeBSD ELF64, nmount), rip = 0x80079a57c, rsp = 0x7fffffffe8
28, rbp = 0x65a9d0 ---
lock order reversal:
 1st 0xffffff002347f668 ntfs (ntfs) @ kern/vfs_subr.c:2061
 2nd 0xffffff00232f2650 vfslock (vfslock) @ kern/vfs_subr.c:364
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
witness_checkorder() at witness_checkorder+0x606
_lockmgr() at _lockmgr+0x4cb
vfs_busy() at vfs_busy+0xdf
vfs_donmount() at vfs_donmount+0x9aa
nmount() at nmount+0xa4
syscall() at syscall+0x1ce
Xfast_syscall() at Xfast_syscall+0xab
--- syscall (378, FreeBSD ELF64, nmount), rip = 0x80079a57c, rsp = 0x7fffffffe8
28, rbp = 0x65ad80 ---

Instead of getting the lstat panic, I am now getting the following
panic when /usr/local/etc/cvsup/update.sh ran:

Fatal trap 9: general protection fault while in kernel mode
cpuid = 0; apic id = 00
instruction pointer     = 0x8:0xffffffff80301051
stack pointer           = 0x10:0xffffffffd6bb0100
frame pointer           = 0x10:0xffffffffd6bb0190
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = resume, IOPL = 0
current process         = 1243 (cvsup)
panic: Assertion !mtx_owned(&w_mtx) failed at ../../../kern/subr_witness.c:959
cpuid = 0
Uptime: 11m14s
Physical memory: 2031 MB
Dumping 325 MB: 310 294 278 262 246 230 214 198 182 166 150 134 118 102 86 70 54
 38 22 6

#0  doadump () at pcpu.h:194
194             __asm __volatile("movq %%gs:0,%0" : "=r" (td));

Scot