Date: Wed, 15 Apr 2009 07:30:01 -0700
From: Arjan van de Ven <arjan@infradead.org>
To: Mark Lord <lkml@rtr.ca>
Cc: Greg KH <greg@kroah.com>, Jeff Garzik <jeff@garzik.org>,
       Linux USB kernel mailing list <linux-usb@vger.kernel.org>,
       Alan Stern <stern@rowland.harvard.edu>,
       LKML <linux-kernel@vger.kernel.org>, "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: USB storage no-boot regression (bisected)
Message-ID: <20090415073001.503b0361@infradead.org>
In-Reply-To: <49E5EE41.3090505@rtr.ca>
References: <49E4FAC6.1030400@garzik.org>
	<20090415014930.GA29413@kroah.com>
	<49E5480F.10501@garzik.org>
	<20090415050947.GB3462@kroah.com>
	<49E5EE41.3090505@rtr.ca>
Organization: Intel
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On Wed, 15 Apr 2009 10:25:05 -0400
Mark Lord <lkml@rtr.ca> wrote:

> Greg KH wrote:
> > ..
> > The issue is that you were just lucky that your machine worked
> > properly previously.  My boxes with the same type of setup didn't,
> > so I quickly realized what the root delay boot option was for.  You
> > need to just do the same thing here, there's nothing else we can do.
> ..
> 
> Bad excuse.
> 
> SATA drives also take variable amounts of time to "show up" at boot.
> Perhaps Jeff should customize libata for your and Arjan's exact
> setups, just to help with understanding the point here.  :)

the difference is that with sata you know when you are done and have all
possible drives. No so much much with USB. So with SATA we can, and do,
wait for the scan to complete at the right point in the boot.

> 
> The speed ups are fine (and welcome), but we really now need
> Arjan to follow-up with a patch to have the kernel *by default*
> wait a little longer for the rootfs to show up.
> 
> Not forever, just a few seconds to compensate for the regression.

seconds!!!!!
The whole kernel boots in half a second!

for this case, which is unfortunately not detectable by the kernel,
there is the rootwait option.

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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