Re: USB storage no-boot regression (bisected)

Greg KH
2009-04-15T01:53:30Z

On Tue, Apr 14, 2009 at 05:06:14PM -0400, Jeff Garzik wrote:
>
> Once of the x86-64 machines I use for testing runs off of two 2GB USB
> flash drives, one for Fedora 10 userland, and one for kernel repository
> + builds.
>
> It boots correctly in 2.6.27, but fails with the same symptoms in
> 2.6.28, 2.6.29 and 2.6.30-rc1:
>
> 1) The kernel boots
> 2) After time passes, kernel begins executing initramfs
> userland
> 3) the kernel prints out probe messages for the USB keyboard,
> SCSI probe messages for the two USB flash drives
>
> Or IOW, the keyboard and two SCSI drives appear after initramfs begins
> booting. And this is for drivers built into the kernel (though same
> behavior with modules).
>
> This no-boot regression is 100% reproducible, and neatly bisects down to
>
> > commit 8520f38099ccfdac2147a0852f84ee7a8ee5e197
> > Author: Alan Stern <stern@rowland.harvard.edu>
> > Date: Mon Sep 22 14:44:26 2008 -0400
> >
> > USB: change hub initialization sleeps to delayed_work
> >
> > This patch (as1137) changes the hub_activate() routine, replacing the
> > power-power-up and debounce delays with delayed_work calls. The idea
> > is that on systems where the USB stack is compiled into the kernel
> > rather than built as modules, these delays will no longer block the
> > boot thread. At least 100 ms is saved for each root hub, which can
> > add up to a significant savings in total boot time.
> >
> > Arjan van de Ven was very pleased to see that this shaved 700 ms off
> > his computer's boot time. Since his total boot time is on the order
> > of two seconds, the improvement is considerable.
> >
> > Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> > Tested-by: Arjan van de Ven <arjan@infradead.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>
>
> My preliminary guess is that this made things --too-- asynchronous, and
> for some reason userland begins executing before the SCSI core
> initializes the USB storage as Linux block devices.
>
> In any case, I cannot boot because of the above commit :)

Like Arjan said, this is because we are initializing faster now, and
things are a bit more asynchronous. Use the root_delay boot option,
that's what I use for my USB-based systems, and have not had a problem
with that at all.

thanks,

greg k-h