linux-kernel - Re: [PATCH 0/5] V2 usb console improvements series

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Message-ID: <Pine.LNX.4.44L0.1003171027501.1734-100000@iolanthe.rowland.org>
Date:	Wed, 17 Mar 2010 10:30:52 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Jason Wessel <jason.wessel@...driver.com>
cc:	gregkh@...e.de, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] V2 usb console improvements series

On Tue, 16 Mar 2010, Jason Wessel wrote:

> Part of having the console stable requires that usb sysrq handler get
> executed in a tasklet.  The hcd device lock is always held while the
> driver call backs are executed.  The means you cannot get the sysrq
> printk's out to the usb console device after the in_flight urb queue
> is filled.

Either I don't understand this comment properly or else it is simply
wrong.  HCDs do not continue to hold their locks when handing completed
URBs back to drivers.  The giveback call occurs with interrupts
disabled, but no locks are held.

Does this mean one of the patches in your series can be simplified?

Alan Stern

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