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    SubjectRe: USB storage no-boot regression (bisected)
    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


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