linux-kernel - Re: [PATCH] usb ehci_iaa

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Date:	Wed, 2 Apr 2008 12:48:36 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Mark Lord <lkml@....ca>
cc:	David Brownell <david-b@...bell.net>, <pavel@...e.cz>,
	<oliver@...kum.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <jikos@...e.cz>, <gregkh@...e.de>,
	<akpm@...ux-foundation.org>
Subject: Re: [PATCH] usb ehci_iaa_watchdog fix

On Wed, 2 Apr 2008, Mark Lord wrote:

> Yup, that does indeed cure it.
> Here's a patch, in case you didn't already generate one:
> 
> Signed-off-by: Mark Lord <mlord@...ox.com>
> 
> --- rc8/drivers/usb/host/ehci-hcd.c	2008-03-11 11:18:40.000000000 -0400
> +++ linux/drivers/usb/host/ehci-hcd.c	2008-04-02 12:16:40.000000000 -0400
> @@ -289,9 +289,7 @@
>  	 * (a) SMP races against real IAA firing and retriggering, and
>  	 * (b) clean HC shutdown, when IAA watchdog was pending.
>  	 */
> -	if (ehci->reclaim
> -			&& !timer_pending(&ehci->iaa_watchdog)
> -			&& HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
> +	if (ehci->reclaim && !timer_pending(&ehci->iaa_watchdog)) {
>  		u32 cmd, status;
>  
>  		/* If we get here, IAA is *REALLY* late.  It's barely

Okay, I'm puzzled.  How could this make any difference?  
ehci_bus_suspend() calls end_unlink_async() anyway, whenever reclaim is 
set.

Is the real problem that it does so before calling ehci_work() instead 
of after calling ehci_halt()?

Mark, if you want to experiment some more, try reverting your patch 
above and moving:

	if (ehci->reclaim)
		end_unlink_async(ehci);

in ehci-hub.c:ehci_bus_suspend() to just after the line saying:

	hcd->state = HC_STATE_SUSPENDED;

Alan Stern

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