Re: udev taking a long time during startup

[Kay Sievers <kay.sievers@vrfy.org>]

On Wed, 2006-08-02 at 22:04 -0700, Piet Delaney wrote:
> On Wed, 2006-08-02 at 10:57 +0200, Kay Sievers wrote:
> > On Tue, 2006-08-01 at 00:16 -0700, Piet Delaney wrote:
> > > We were wondering why there is a 60 second delay on our systems
> > > from the time that the kernel releases memory and the file system 
> > > is checked.
> > > 
> > > I dropped into kgdb during this period and found that an init
> > > script, S10udev in our case, was sleeping in sys_nanosleep()
> > > or sys_wait4(). Looks like thread/process S10udev forks udevstart
> > > which forks udev which appears to be sleeping or waiting every time
> > > I check in on it; Seems terribly wasteful.
> > > 
> > > udev seems to be a utility for hotplug and configured
> > > with /etc/udev/udev.conf. Since we have no hot plug devices
> > > I wonder if it really has to be called on every startup. On
> > > solaris the device nodes are only re-established if you boot
> > > with a -r option.
> > > 
> > > I never see any children of udev, so I wonder why it's
> > > calling wait4() and nanosleep() so often.
> > 
> > You may check with your distro, that sounds like a broken setup. And
> > please ask further questions on: linux-hotplug-devel@lists.sourceforge.net
> 
> Yep, look like LFS linux-hotplug Developers Lists might be a good idea.
> 
> Looks like we must be using a LFS version prior to 6.1.1, as
> we are using udev 030. I tried the latest 096 and installed it
> in /usr/local. Was getting a bit tied on upgrading the config
> and rule files to the new "=" convention for KERNEL and just installed
> 030 in /usr/local so I could use the existing config and rules for now.
> 
> Booted fine with new udev utils from src with debug going
> to /var/log/messages. As expected I saw a lot of nanosleeps,
> a few for what appeared to be more than 10 iterations of 10 msec.
> 
> Since succeeding cases seemed to pass within 2 or 3 iterations of 
> 10 msec I tried decreasing the loops (for us) to 5 iterations of 5 
> msec. So far I don't see a problem or a substantial improvement; 
> at least not with the tracing enabled.
> 
> We are using the 2.6.12 thru 2.6.15 kernels and are based on the stable
> linux from scratch (LFS) pre 6.1.1 distro; I think it's 6.1; we
> shouldn't be running on such an old distro (support gets hard).
> 
>         http://www.linuxfromscratch.org/
> 
> in the future I guess we will migrate to the development LFS distro
> which is currently useing udev-096 and linux 2.6.16.27.
>                 
> 
> Tonight I tried udev 096 to /usr/local/ and installed the 
> LFS udev-config-6.2.tar rules.
> 
> Syslog is showing some confusion with an exising daemon running:
> ----------------------------------------------------------------
> Aug  2 20:38:53 localhost udevsend[1794]: starting udevd daemon
> Aug  2 20:38:53 localhost udevd[1796]: udev_config_init:
> UDEV_CONFIG_FILE='/usr/local/etc/udev/udev.conf'
> Aug  2 20:38:53 localhost udevd[1796]: udev_config_init:
> udev_root='/dev'
> Aug  2 20:38:53 localhost udevd[1796]: udev_config_init:
> udev_rules='/usr/local/etc/udev/rules.d'
> Aug  2 20:38:53 localhost udevd[1796]: udev_config_init: udev_log=7
> Aug  2 20:38:53 localhost udevd[1796]: main: version 096
> Aug  2 20:38:53 localhost udevd[1796]: init_udevd_socket: bind failed:
> Address already in use

Ugh, disable /proc/sys/kernel/hotplug and get rid of udevsend? All that
old stuff can't, and never worked reliably and should be disabled.

Kay


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