Re: panic: mutex Giant owned at nfs_syscalls.c:556

On 21/02/2008, Kris Kennaway <kris_at_freebsd.org> wrote:
> pluknet wrote:
>  > I got this assertion while attempting to remove file on nfs mounted
>  > ffs filesystem.
>  > NFS client on 7.0-PRERELEASE and NFS server on 8-CURRENT.
>  >
>  > FreeBSD 7.0-PRERELEASE #1: Wed Feb  6 18:09:18 MSK 2008
>  > FreeBSD 8.0-CURRENT #9: Fri Feb 15 14:31:07 MSK 2008
>  >
>  > Unread portion of the kernel message buffer:
>  > panic: mutex Giant owned at
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:556
>  > KDB: enter: panic
>  > exclusive sleep mutex nfsd_mtx r = 0 (0xc41d1660) locked _at_
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:501
>  > exclusive sleep mutex Giant r = 0 (0xc07e6410) locked _at_
>  > /usr/src/sys/kern/vfs_lookup.c:663
>  > ...
>  > #9  0xc053959d in panic (fmt=0xc076181d "mutex %s owned at %s:%d")
>  >     at /usr/src/sys/kern/kern_shutdown.c:555
>  > #10 0xc052adf7 in _mtx_assert (m=0xc07e6410, what=0,
>  >     file=0xc41cb7b2
>  > "/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c",
>  > line=556) at /usr/src/sys/kern/kern_mutex.c:652
>  > #11 0xc41c9e82 in nfssvc (td=0xc2e68000, uap=0xd600dcfc)
>  >     at /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:556
>  > #12 0xc0727903 in syscall (frame=0xd600dd38)
>  >     at /usr/src/sys/i386/i386/trap.c:1034
>  > #13 0xc0711630 in Xint0x80_syscall () at /usr/src/sys/i386/i386/exception.s:203
>  > ---Type <return> to continue, or q <return> to quit---
>  > #14 0x00000033 in ?? ()
>  >
>  > Looks somewhat strange because nfs_syscalls.c:556 is not in nfssvc(),
>  > it's in nfssvc_nfsd().
>  > Kernel and world synchronized on 8-CUR though.
>  >
>
>
> This has been reported a couple of times before but you are the first to
>  provide the WITNESS data, which was necessary to proceed.  Thanks :)
>
>  So there are two questions:
>
>  1) Why is Giant being acquired at all?  vfs_lookup.c:663 is a
>  VFS_LOCK_GIANT indicating that you are doing a lookup on a non-mpsafe
>  filesystem.  What filesystems are being exported by the server?
>  Previously people claimed not to be exporting any filesystems that
>  should be marked !mpsafe, which was a puzzle.
>

I'm sorry for confusing you. :/ Actually 1 msdosfs filesystem is being exported.
BTW panic occurred on UP kernel.

>  2) Missed VFS_UNLOCK_GIANT somewhere, or broken assert.  The above trace
>  should be enough to diagnose though.
>

I will try to reproduce and investigate this (in a week).

>
>  Kris
>

wbr,
pluknet