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

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Message-Id: <200805211540.25135.oliver@neukum.org>
Date:	Wed, 21 May 2008 15:40:24 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Jiri Kosina <jkosina@...e.cz>
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

Am Mittwoch 21 Mai 2008 15:27:50 schrieb Jiri Kosina:
> 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().
> 

Sorry, yes other code paths take it with enabled interrupts.
The patch is good and necessary for 2.6.26.

	Regards
		Oliver

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