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Date:      Thu, 16 May 2002 19:01:08 -0500
From:      Dave Baukus <dbaukus@chiaro.com>
To:        fs@freebsd.org
Subject:   panic("unmount: dangling vnode");
Message-ID:  <3CE44844.3050603@chiaro.com>
References:  <3CE44716.60C4AA@chiaro.com>

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I hit the following panic:
         panic("unmount: dangling vnode");
 
in vfs_syscalls.c - dounmount() with a high degree of regularity.
I am running what is essentially bsd4.0; the networking stack
has been modified, but the file system, proc, virtual memory, ... are
untouched.

I was wondering if this panic has been addressed in other releases.
The panic is related to rebooting the system while one or more processes
is/are core dumping: 

... max 60 seconds) for system process `bufdaemon' to stop...stopped
Waiting (max 60 seconds) for system process `syncer' to stop...stopped
syncing disks... 24 
done
pid 2391 (protmon), uid 0: exited on signal 11 (core dumped)
pid 2661 (soclone_mcp), uid 0: exited on signal 11 (core dumped)
spec_fsync: dirty: 0xd4997f60: type VBLK, usecount 2, writecount 0, refcount 35,
flags (VOBJBUF)
panic: unmount: dangling vnode
Debugger("panic")
Stopped at      Debugger+0x35:  movb    $0,in_Debugger.390
db> gdb
Next trap will enter GDB remote protocol mode
db> s

(kgdb) bt
#0  Debugger (msg=0xc030ff1b "panic") at ../../i386/i386/db_interface.c:321
#1  0xc017b74c in panic (fmt=0xc0315486 "unmount: dangling vnode")
    at ../../kern/kern_shutdown.c:577
#2  0xc01ac7c8 in dounmount (mp=0xc363ec00, flags=524288, p=0xd499c440)
    at ../../kern/vfs_syscalls.c:508
#3  0xc01ab202 in vfs_unmountall () at ../../kern/vfs_subr.c:2207
#4  0xc017b2ff in boot (howto=0) at ../../kern/kern_shutdown.c:292
#5  0xc017af04 in reboot (p=0xd499c440, uap=0xd5346f80)
    at ../../kern/kern_shutdown.c:148
#6  0xc02e609e in syscall (frame={tf_fs = 47, tf_es = 47, tf_ds = 47, 
      tf_edi = 1, tf_esi = 0, tf_ebp = -1077936884, tf_isp = -717983788, 
      tf_ebx = 0, tf_edx = -1077936630, tf_ecx = -143, tf_eax = 55, 
      tf_trapno = 12, tf_err = 2, tf_eip = 134515276, tf_cs = 31, 
      tf_eflags = 647, tf_esp = -1077936928, tf_ss = 47})
    at ../../i386/i386/trap.c:1073
#7  0xc02d7b36 in Xint0x80_syscall ()
#8  0x80480f9 in ?? ()

(kgdb) up 
#1  0xc017b74c in panic (fmt=0xc0315486 "unmount: dangling vnode")
    at ../../kern/kern_shutdown.c:577
577                     Debugger ("panic");
(kgdb) 
#2  0xc01ac7c8 in dounmount (mp=0xc363ec00, flags=524288, p=0xd499c440)
    at ../../kern/vfs_syscalls.c:508
508                     panic("unmount: dangling vnode");
(kgdb) p mp
$1 = (struct mount *) 0xc363ec00
(kgdb) p /x *mp
$2 = {mnt_list = {tqe_next = 0x0, tqe_prev = 0xc035f204}, mnt_op = 0xc038dea0, 
  mnt_vfc = 0xc038dee0, mnt_vnodecovered = 0x0, mnt_syncer = 0x0, 
  mnt_vnodelist = {lh_first = 0xd4996980}, mnt_lock = {lk_interlock = {
      lock_data = 0x0}, lk_flags = 0x1004400, lk_sharecount = 0x0, 
    lk_waitcount = 0x0, lk_exclusivecount = 0x1, lk_prio = 0x14, 
    lk_wmesg = 0xc0314fc2, lk_timo = 0x0, lk_lockholder = 0xdb7}, 
  mnt_flag = 0x4000, mnt_kern_flag = 0x1000000, mnt_maxsymlinklen = 0x3c, 
  mnt_stat = {f_spare2 = 0x0, f_bsize = 0x400, f_iosize = 0x2000, 
    f_blocks = 0x7b850, f_bfree = 0x64ab2, f_bavail = 0x5ac98, 
    f_files = 0x1effe, f_ffree = 0x1e9b0, f_fsid = {val = {0x3c6d2248, 
        0x6774c663}}, f_owner = 0x0, f_type = 0x2, f_flags = 0x5000, 
    f_syncwrites = 0x17, f_asyncwrites = 0x2c, f_fstypename = {0x75, 0x66, 
      0x73, 0x0 <repeats 13 times>}, f_mntonname = {0x2f, 
      0x0 <repeats 79 times>}, f_syncreads = 0xdd, f_asyncreads = 0x9, 
    f_spares1 = 0x0, f_mntfromname = {0x2f, 0x64, 0x65, 0x76, 0x2f, 0x61, 
      0x64, 0x30, 0x73, 0x31, 0x61, 0x0 <repeats 69 times>}, f_spares2 = 0x0, 
    f_spare = {0x0, 0x0}}, mnt_data = 0x0, mnt_time = 0x3cd19482, 
  mnt_iosize_max = 0x20000}


-- 
dave baukus@chiaro.com
Chiaro Networks
Richardson Texas
USA

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