panic: mutex Giant owned at nfs_syscalls.c:556

pluknet pluknet at gmail.com
Mon Mar 3 02:41:36 UTC 2008


On 20/02/2008, pluknet <pluknet at gmail.com> wrote:
[snip]
>  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 @
>  /usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:501
>  exclusive sleep mutex Giant r = 0 (0xc07e6410) locked @
>  /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 ?? ()

[Some new info probably not related to the thread.]
Today I got two new panics while performing /etc/rc.d/nfsd stop:

System call nfssvc returning with the following locks held:
exclusive sleep mutex Giant r = 2 (0xc07e6410) locked @
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c:1106
panic: witness_warn
...
#9  0xc053959d in panic (fmt=0xc076791b "witness_warn")
    at /usr/src/sys/kern/kern_shutdown.c:555
#10 0xc056ff99 in witness_warn (flags=2, lock=0x0,
    fmt=0xc0789975 "System call %s returning")
    at /usr/src/sys/kern/subr_witness.c:1396
#11 0xc0727a56 in syscall (frame=0xd5f9ed38)
    at /usr/src/sys/i386/i386/trap.c:1083
#12 0xc0711630 in Xint0x80_syscall () at /usr/src/sys/i386/i386/exception.s:203
#13 0x00000033 in ?? ()

The second is different only in place where Giant is acquired.
System call nfssvc returning with the following locks held:
exclusive sleep mutex Giant r = 0 (0xc07e6410) locked @
/usr/src/sys/kern/vfs_lookup.c:663
panic: witness_warn


On 21/02/2008, Kris Kennaway <kris at freebsd.org> wrote:
>  Hopefully it should be a straightforward fix to track down which code
>  path is missing the VFS_UNLOCK_GIANT() to reach the above stack trace,
>  or to reproduce.

I've marked VFS_[UN]LOCK_GIANT() in nfs_(serv|srvsubs).c with
appropriate printf()'s:
$ rm 123vfslocked lock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c, 1106
vfslocked unlock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 253

vfslocked lock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_srvsubs.c, 1106
vfslocked unlock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 253
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
vfslocked unlock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 648
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
vfslocked unlock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 648
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
vfslocked unlock in
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_serv.c, 2234
panic: mutex Giant owned at
/usr/src/sys/modules/nfsserver/../../nfsserver/nfs_syscalls.c:556

So, Giant is acquired in nfs_srvsubs.c:1106 and is not released in
nfs_serv.c:648
Btw, I cannot reproduce it with module compiled via
cd /sys/modules/nfsserver; make all && make install

On 23/02/2008, Kostik Belousov <kostikbel at gmail.com> wrote:
> Assert itself only catches the missed Giant unlock somewhere during
>  the execution of an nfs requtest.
>  Unfortunately, it seems that the error is in nfsserver that missed
>  Giant unlock (most likely, on some error path). Helpful would be
>  the tcpdump raw trace file of the communication between nfs server and
>  client immediately before the panic.

Here it is (with -xvvn). [I can reproduce the panic only when I try to
delete a file on nfs.]

03:07:59.342714 IP (tos 0x0, ttl 128, id 39253, offset 0, flags
[none], proto UDP (17), length 136) 192.168.200.185.1968921799 >
192.168.200.137.2049: 108 access [|nfs]
        0x0000:  4500 0088 9955 0000 8011 8e7b c0a8 c8b9
        0x0010:  c0a8 c889 03f8 0801 0074 3c9e 755b 5cc7
        0x0020:  0000 0000 0000 0002 0001 86a3 0000 0003
        0x0030:  0000 0004 0000 0001 0000 0020 0000 0000
        0x0040:  0000 0000 0000 03e9 0000 03e9 0000 0003
        0x0050:  0000
03:07:59.343818 IP (tos 0x0, ttl 128, id 30823, offset 0, flags
[none], proto UDP (17), length 148) 192.168.200.137.2049 >
192.168.200.185.1968921799: reply ok 120 access attr: REG 755 ids
1001/0 [|nfs]
        0x0000:  4500 0094 7867 0000 8011 af5d c0a8 c889
        0x0010:  c0a8 c8b9 0801 03f8 0080 1bda 755b 5cc7
        0x0020:  0000 0001 0000 0000 0000 0000 0000 0000
        0x0030:  0000 0000 0000 0000 0000 0001 0000 0001
        0x0040:  0000 01ed 0000 0001 0000 03e9 0000 0000
        0x0050:  0000
03:07:59.344297 IP (tos 0x0, ttl 128, id 20293, offset 0, flags
[none], proto UDP (17), length 140) 192.168.200.185.1968921800 >
192.168.200.137.2049: 112 lookup [|nfs]
        0x0000:  4500 008c 4f45 0000 8011 d887 c0a8 c8b9
        0x0010:  c0a8 c889 03f8 0801 0078 58a1 755b 5cc8
        0x0020:  0000 0000 0000 0002 0001 86a3 0000 0003
        0x0030:  0000 0003 0000 0001 0000 0020 0000 0000
        0x0040:  0000 0000 0000 03e9 0000 03e9 0000 0003
        0x0050:  0000
03:07:59.344782 IP (tos 0x0, ttl 128, id 64063, offset 0, flags
[none], proto UDP (17), length 264) 192.168.200.137.2049 >
192.168.200.185.1968921800: reply ok 236 lookup [|nfs]
        0x0000:  4500 0108 fa3f 0000 8011 2d11 c0a8 c889
        0x0010:  c0a8 c8b9 0801 03f8 00f4 feb1 755b 5cc8
        0x0020:  0000 0001 0000 0000 0000 0000 0000 0000
        0x0030:  0000 0000 0000 0000 0000 001c 5100 0000
        0x0040:  0400 0000 0c00 0000 4dc9 1000 8001 0000
        0x0050:  0000
03:07:59.345530 IP (tos 0x0, ttl 128, id 32619, offset 0, flags
[none], proto UDP (17), length 140) 192.168.200.185.1968921801 >
192.168.200.137.2049: 112 lookup [|nfs]
        0x0000:  4500 008c 7f6b 0000 8011 a861 c0a8 c8b9
        0x0010:  c0a8 c889 03f8 0801 0078 58a0 755b 5cc9
        0x0020:  0000 0000 0000 0002 0001 86a3 0000 0003
        0x0030:  0000 0003 0000 0001 0000 0020 0000 0000
        0x0040:  0000 0000 0000 03e9 0000 03e9 0000 0003
        0x0050:  0000
03:07:59.346752 IP (tos 0x0, ttl 128, id 50548, offset 0, flags
[none], proto UDP (17), length 264) 192.168.200.137.2049 >
192.168.200.185.1968921801: reply ok 236 lookup [|nfs]
        0x0000:  4500 0108 c574 0000 8011 61dc c0a8 c889
        0x0010:  c0a8 c8b9 0801 03f8 00f4 feb0 755b 5cc9
        0x0020:  0000 0001 0000 0000 0000 0000 0000 0000
        0x0030:  0000 0000 0000 0000 0000 001c 5100 0000
        0x0040:  0400 0000 0c00 0000 4dc9 1000 8001 0000
        0x0050:  0000
03:07:59.347265 IP (tos 0x0, ttl 128, id 52799, offset 0, flags
[none], proto UDP (17), length 140) 192.168.200.185.1968921802 >
192.168.200.137.2049: 112 remove [|nfs]
        0x0000:  4500 008c ce3f 0000 8011 598d c0a8 c8b9
        0x0010:  c0a8 c889 03f8 0801 0078 5896 755b 5cca
        0x0020:  0000 0000 0000 0002 0001 86a3 0000 0003
        0x0030:  0000 000c 0000 0001 0000 0020 0000 0000
        0x0040:  0000 0000 0000 03e9 0000 03e9 0000 0003
        0x0050:  0000
03:07:59.348654 IP (tos 0x0, ttl 128, id 55143, offset 0, flags
[none], proto UDP (17), length 172) 192.168.200.137.2049 >
192.168.200.185.1968921802: reply ok 144 remove PRE: [|nfs]
        0x0000:  4500 00ac d767 0000 8011 5045 c0a8 c889
        0x0010:  c0a8 c8b9 0801 03f8 0098 1757 755b 5cca
        0x0020:  0000 0001 0000 0000 0000 0000 0000 0000
        0x0030:  0000 0000 0000 0000 0000 0001 0000 0000
        0x0040:  0000 4000 4099 2bf4 0000 0000 4099 2bf4
        0x0050:  0000

wbr,
pluknet


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