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

On 03/03/2008, Kostik Belousov <kostikbel_at_gmail.com> wrote:
> On Mon, Mar 03, 2008 at 09:27:15PM +0300, pluknet wrote:
>  > On 03/03/2008, Kostik Belousov <kostikbel_at_gmail.com> wrote:
>  > [snip]
>  > >  To summarize, I need both the tcpdump and kernel/witness messages from
>  > >  the panic.
>  > >
>  >
>  > I'm sorry. Here it is.
>  > http://pluknet.nm.ru/dev/tcpdump-nfsserver-full.raw
>  >
>  > The messages (same as unread msgbuf in initial posting, hand-scribed):
>  > panic: mutex Giant owned at
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:556
>  > KDB: enter: panic
>  > [thread pid 601 tid 100055 ]
>  > Stopped at kdb_enter+0x3a: movl $0,kdb_why
>  > db> show locks
>  > exclusive sleep mutex nfsd_mtx r = 0 (0xc2e0af40) 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
>  >
>  > >  Nevertheless, the patch below might help with the panic during
>  > >  the unlinking (not tested).
>  > >
>  > >  diff --git a/sys/nfsserver/nfs_serv.c b/sys/nfsserver/nfs_serv.c
>  > >  index 446651d..87e1aaa 100644
>  > >  --- a/sys/nfsserver/nfs_serv.c
>  > >  +++ b/sys/nfsserver/nfs_serv.c
>  > >  _at__at_ -2146,7 +2146,7 _at__at_ nfsrv_remove(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
>  > >         nfsfh_t nfh;
>  > >         fhandle_t *fhp;
>  > >         struct mount *mp = NULL;
>  > >  -       int vfslocked;
>  > >  +       int vfslocked, vfslocked1;
>  > >
>  > >         nfsdbprintf(("%s %d\n", __FILE__, __LINE__));
>  > >         ndclear(&nd);
>  > >  _at__at_ -2168,7 +2168,11 _at__at_ nfsrv_remove(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
>  > >         nd.ni_cnd.cn_flags = LOCKPARENT | LOCKLEAF | MPSAFE;
>  > >         error = nfs_namei(&nd, fhp, len, slp, nam, &md, &dpos,
>  > >                 &dirp, v3,  &dirfor, &dirfor_ret, td, FALSE);
>  > >  -       vfslocked = NDHASGIANT(&nd);
>  > >  +       vfslocked1 = NDHASGIANT(&nd);
>  > >  +       if (vfslocked && vfslocked1)
>  > >  +               VFS_UNLOCK_GIANT(vfslocked1);
>  > >  +       if (vfslocked || vfslocked1)
>  > >  +               vfslocked = 1;
>  > >         if (dirp && !v3) {
>  > >                 vrele(dirp);
>  > >                 dirp = NULL;
>  > >
>  > >
>  >
>  > Now the last lock triplex looks like:
>  > vfslocked lock in
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 2161
>  > vfslocked lock in
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c, 1106
>  > vfslocked lock in
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c, 673
>  > vfslocked unlock in
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c, 916
>  > vfslocked1 unlock in
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 2173
>  > ^^^
>  > vfslocked unlock in
>  > /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 2238
>  >
>  > And no panic. Thanks.
>
>
> Could you, please, clarify. As I read you mail, the patch fixed at least
>  one of your panic. Are there any other situations where nfs server over
>  non-MPSAFE fs panics for you ? It is possible that what you reported
>  before actually contains several different reasons for Giant leak.

Of course.
That another situation is while performing /etc/rc.d/nfsd stop
> System call nfssvc returning with the following locks held:
> exclusive sleep mutex Giant r = 2 (0xc07e6410) locked _at_
> /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c:1106
> panic: witness_warn

I got no panic with this patch:
# /etc/rc.d/nfsd stop
Stopping nfsd.
kill: 1737: No such process
kill: 1738: No such process
kill: 1739: No such process
kill: 1740: No such process
#

wbr,
pluknet