Re: Hanging udev process on nfs-mounted /dev

[Frank Steiner <fsteiner-mail@bio.ifi.lmu.de>]

Kay Sievers wrote

>>boot.udev is run on boot, so it recreates the database on every start,
>>and thus, it looks like it gets corrupted again on almost every boot.
> 
> 
> Weird! Please double check that this script is really running. There is
> nothing in the boot.msg file, but I don't know if there should be some.

It is definitely running: The link is in boot.d:
noether /root# ls -la /etc/init.d/boot.d/S01boot.udev
lrwxrwxrwx    1 root     root           12 2004-09-30 08:57 /etc/init.d/boot.d/S01boot.udev -> ../boot.udev

and boot.udev contains:
case "$1" in
     start)
    if [ -x /sbin/udev -a -x /sbin/udevstart ] ; then
     echo -n "creating device nodes "
     rm -f /dev/.udev.tdb
     /sbin/udevstart

You can also see this in the strace log of the first udev process,
which is the last on the page (the lowest pid number). The first
line of this strace is
1037  execve("/sbin/utest/udevstart", ["/sbin/utest/udevstart"], [/* 174 vars */]) = 0

A general question for understanding things better: Let's assume that
the errors indeed are caused by missing nfs locking on my /dev dir.
It sounds reasonable that udev must be able to rely on propper locking
for maintaining its database, so one should not expect it to work on
a fs without locking.
Would it be reasonable to issue a warning if udev detects it's running
on a fs without locking (if this is possible to detect)? Or, if in
case of missing locks the hangs cannot be prevented, udev could even
refuse to do any work. If one gets a message from udev "No locks available.
I will not create any devices until you give  me locks" this would
definitely help people doing stupid things like mounting /dev via NFS :-)

I'm still trying to get another host hanging, so that I can login and
call gdb. I'll let you know if it happens :-)

cu,
Frank





-- 
Dipl.-Inform. Frank Steiner   Web:  http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik    Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr. 17           Phone: +49 89 2180-4049
80333 Muenchen, Germany       Fax:   +49 89 2180-99-4049
* Rekursion kann man erst verstehen, wenn man Rekursion verstanden hat. *


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