linux-kernel - Re: [PATCH RFC] USB: Add HCD fastboot

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Message-ID: <Pine.LNX.4.44L0.0808061508430.12900-100000@iolanthe.rowland.org>
Date:	Wed, 6 Aug 2008 15:11:08 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Simon Arlott <simon@...e.lp0.eu>
cc:	Rene Herman <rene.herman@...access.nl>,
	Arjan van de Ven <arjan@...radead.org>,
	<linux-kernel@...r.kernel.org>, <mingo@...e.hu>,
	Daniel Walker <dwalker@...sta.com>,
	USB list <linux-usb@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [PATCH RFC] USB: Add HCD fastboot

On Wed, 6 Aug 2008, Simon Arlott wrote:

> On 31/07/08 20:16, Alan Stern wrote:
> >> > It's not entirely clear why usblp is blocking at all.  Probably because
> >> > it is waiting on the device semaphores for devices that are currently
> >> > being probed -- the driver core won't allow two threads to probe the
> >> > same device concurrently.
> >> 
> >> Ok - so there could be some big improvements to be had by making the hcd 
> >> init happen as early as possible and the device initcalls later?
> > 
> > Maybe.  Perhaps a better approach would be to make the device driver 
> > initcalls before there are any devices for their probe routines to 
> > block on.
> 
> What about this?
> 
> The Makefiles become a bit messy, but by moving things around I get the 
> desired effect without splitting their initcalls.

Wouldn't it be much simpler, and less objectionable, to do what I
suggested earlier?  That is, add a 5-second delay at the start of
hub_thread() in drivers/usb/core/hub.c.  No messing with Makefiles, no
changes to the initcall scheduling.

Alan Stern

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