linux-kernel - Re: [PATCH] USB: fix deadlock in HCD code

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Message-ID: <Pine.LNX.4.64.0805211524130.6718@jikos.suse.cz>
Date:	Wed, 21 May 2008 15:27:50 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Greg KH <greg@...ah.com>, linux-usb@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>, lchiquitto@...ell.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: fix deadlock in HCD code

On Wed, 21 May 2008, Oliver Neukum wrote:

> > hcd_urb_list_lock is used for synchronization between IRQ and non-IRQ 
> > contexts, so the non-IRQ context has to disable IRQs in order to prevent 
> > deadlocking with IRQ context.
> Which non-irq context is that?

One example -- assume usb_submit_urb() called from non-IRQ context. Then

usb_hcd_submit_urb() -> rh_urb_enqueue() -> rh_queue_status() -> 
usb_hcd_link_urb_to_ep().

-- 
Jiri Kosina
SUSE Labs
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