From mboxrd@z Thu Jan  1 00:00:00 1970
From: Greg KH <greg@kroah.com>
Date: Fri, 15 Oct 2004 22:12:44 +0000
Subject: Re: strange delays in vc class
Message-Id: <20041015221244.GA27482@kroah.com>
List-Id: <linux-hotplug.vger.kernel.org>
References: <20041015000446.GA2796@vrfy.org>
In-Reply-To: <20041015000446.GA2796@vrfy.org>
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To: linux-hotplug@vger.kernel.org

On Fri, Oct 15, 2004 at 09:18:26PM +0200, Kay Sievers wrote:
> On Fri, Oct 15, 2004 at 11:59:35AM -0700, Greg KH wrote:
> > On Fri, Oct 15, 2004 at 08:48:39PM +0200, Kay Sievers wrote:
> > > On Fri, Oct 15, 2004 at 11:34:33AM -0700, Greg KH wrote:
> > > > On Fri, Oct 15, 2004 at 02:23:53AM +0200, Kay Sievers wrote:
> > > > > On Fri, Oct 15, 2004 at 02:04:46AM +0200, Kay Sievers wrote:
> > > > > > I've some debug output from a patched wait_for_sysfs. But no id=
ea,
> > > > > > what's going wrong here:
> > > > >=20
> > > > > Ok, there is a pattern. Seems pretty strange to get _two_ hotplug=
 events
> > > > > for the same device. Only the second event will create the "dev" =
file we're
> > > > > looking for. So the first event will spin until the second arrive=
s with the file.
> > > >=20
> > > > Is this with the -mm tree?  or a "clean" 2.6.9-rc4 kernel?
> > >=20
> > > It happens with a 2.6.8 kernel.
> >=20
> > Ugh.  In looking at the kernel code, I don't see how it could be doing
> > this.  But the console startup code is a strange beast...
>=20
> I'm getting closer:
> This is the sequence I get on bootup:
>=20
>   SUBSYSTEM=3Dnet
>   DEVPATH=3D/class/net/sit0
>   SEQNUM&0
>   ACTION=ADd
>=20
>   SUBSYSTEM=3Dvc
>   DEVPATH=3D/class/vc/vcs4
>   SEQNUM&1
>   ACTION=ADd
>=20
>   SUBSYSTEM=3Dvc
>   DEVPATH=3D/class/vc/vcsa4
>   SEQNUM&2
>   ACTION=ADd
>=20
>   SUBSYSTEM=3Dvc
>   DEVPATH=3D/class/vc/vcs4
>   SEQNUM&3
>   ACTION=3Dremove
>=20
>   SUBSYSTEM=3Dvc
>   DEVPATH=3D/class/vc/vcsa4
>   SEQNUM&4
>   ACTION=3Dremove
>=20
>   SUBSYSTEM=3Dvc
>   DEVPATH=3D/class/vc/vcs4
>   SEQNUM&5
>   ACTION=ADd
>=20
>   SUBSYSTEM=3Dvc
>   DEVPATH=3D/class/vc/vcsa4
>   SEQNUM&6
>   ACTION=ADd
>=20
> According to the kernel code the vc is created on open() and destroyed
> on close() which causes hotplug events.  Seems like the bootup opens and
> closes a vc two times for every device.
> The close will remove the "dev" file and the wait_for_sysfs from the
> add-hotplug will spin and fail or at best will recover with the next
> hotplug-add. The "remove" event beats the "add"! We have the same event
> serializing problem here, we solved with udevd for udev.

Heh, no fun.

Ok, I fixed this by watching for the directory to go away from under us.
In my booting I couldn't duplicate these messages anymore...

thanks,

greg k-h


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