Date: Mon, 15 May 2000 23:00:33 +0900 (JST) From: matsunaw@ja2.so-net.ne.jp To: FreeBSD-gnats-submit@freebsd.org Subject: kern/18572: /var/run as mount_mfs w/ soft-updates Message-ID: <200005151400.XAA00613@tsuneko.local>
next in thread | raw e-mail | index | archive | help
>Number: 18572
>Category: kern
>Synopsis: /var/run as mount_mfs w/ soft-updates
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Mon May 15 11:20:00 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator: Hitoshi Matsunawa
>Release: FreeBSD 4.0-RELEASE i386
>Organization:
none
>Environment:
[HW]
CPU: Pentium II/Pentium II Xeon/Celeron (400.91-MHz 686-class CPU)
real memory = 134152192 (131008K bytes)
ad0: 9671MB <IBM-DTTA-351010> [19650/16/63] at ata0-master using UDMA33
[Running daemons]
0 ?? DLs 0:00.00 (swapper)
1 ?? ILs 0:00.01 /sbin/init --
2 ?? DL 0:00.01 (pagedaemon)
3 ?? DL 0:00.00 (vmdaemon)
4 ?? DL 0:00.01 (bufdaemon)
5 ?? DL 0:00.35 (syncer)
27 ?? ILs 0:00.01 mfs -s 8192 /dev/ad0s3b /var/run (mount_mfs)
29 ?? ILs 0:00.02 mfs -s 65536 /dev/ad0s3b /tmp (mount_mfs)
35 ?? Is 0:00.00 adjkerntz -i
81 ?? Ss 0:00.05 syslogd
84 ?? Is 0:00.07 named -q
105 ?? Is 0:00.01 inetd -lwW
107 ?? Is 0:00.03 cron
125 ?? I<s 0:00.00 apmd
[Mounted file systems]
/dev/ad0s2a on / (ufs, local,...)
/dev/ad0s2e on /var (ufs, local, soft-updates,...)
/dev/ad0s3f on /var/data (ufs, local, soft-updates,...)
mfs:27 on /var/run (mfs, asynchronous, local)
mfs:29 on /tmp (mfs, asynchronous, local)
/dev/ad0s2f on /usr (ufs, local, soft-updates,...)
/dev/ad0s3h on /usr/local/src (ufs, local, soft-updates,...)
>Description:
If ``halt''-ed immediately after creating some number of dirty buffer
(may required spread across several file systems), system will fail to
shutdown.
w/ ``sysctl -w debug.busyprt=1'', following messages reported on console:
---->
vflush: busy vnode: 0xc8770e00: type VREG, usecount 1, writecount 0, refcount 1, flag (VOBJBUF)
tag VT_UFS, ino 4, on dev MFS0(253,0)
[in non-deadlock-ed case, two more busy vnode (type of VSOCK) are reported]
message to wait for ``bufdaemon''
message to wait for ``syncer''
syncing disks... 2 2 2 2 2 2 ....
1. dev:MFS0, flags: 00100000 blkno: 48, lblkno: 48
2. dev:MFS0, flags: 01020024 blkno: 64, lblkno: 64
<----
This seems to be caused by ``rundown'' race between mfs process and
other daemons who use "/var/run", and resulted in deadlock. kernel
DDB shows named waiting on "biord" while mfs/syslogd on "inode".
If soft-updates is disabled, no problems occur (in my case). But
soft-updates may only makes the problem easy to happen.
I tried several way to figure out what's going on and/or find out a
work-around:
(1) in mfs_start() (of src/ufs/mfs/mfs_vfops.c), ignoring signals except
SIGKILL.
(2) in mfs_start(), exucutes dounmount() in other execution vehicle
(using kthread_create()).
(3) in biowait() (of src/kern/vfs_bio.c), add a time-out parameter on
tsleep()-call and return EINTER if timed-out.
all of above seems solve the problem for me, but:
(1) user visible changes.
(2) kthread_create() seems not appropriate for this kind purpose.
(3) tried just for curiosity and to support kernel DDB's idea of "who's
waiting on where".
There may be more choices and trade-offs.
>How-To-Repeat:
It's depend on timing. In my case:
% cd $INDEX_of_NAMAZU_as_WEB_SEARCH_ENGINE
% rm *
% sync; sync; sync
% su
# cd /usr/src/sys/compile/$IDENT
# mv kernel /kernel.00
% mknmz -a ~/src/linux-2.3.51/Documentation/
% super halt
where, LANG=ja_JP.EUC, perl (mknmz is written in perl) used is bundled
one.
>Fix:
I only found a few work around (described in [>Description:]).
I think fundamental problem is that once mfs process enters into
dounmount(), mfs i/o won't be served for other processes (other than
mfs process itself). I couldn't find how it's related w/
soft-updates. It's may all about timing but may not.
>Release-Note:
>Audit-Trail:
>Unformatted:
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-bugs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200005151400.XAA00613>