netdev - Re: [PATCH v2] usbnet: enable more aggressive autosuspend

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Message-ID: <Pine.LNX.4.44L0.0810241008060.13114-100000@iolanthe.rowland.org>
Date:	Fri, 24 Oct 2008 10:12:22 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Per Hallsmark <per.hallsmark@...ata.se>
cc:	USB list <linux-usb@...r.kernel.org>, <netdev@...r.kernel.org>,
	David Brownell <david-b@...bell.net>
Subject: Re: [PATCH v2] usbnet: enable more aggressive autosuspend

On Fri, 24 Oct 2008, Per Hallsmark wrote:

> Alan Stern wrote:
> > On Thu, 23 Oct 2008, Per Hallsmark wrote:
> >
> >   
> >> Enable more aggressive autosuspend in usbnet.
> >> Some commenting and cleanups done.
> >> Signed-off-by: Per Hallsmark <per@...lsmark.se>
> >>     
> >
> > I've been considering submitting the patch below.  It would help your 
> > work; you could remove all the "waker" stuff.
> >   

> So, if I understand the patch correctly, the waker's in cdc-acm, cdc-wdm 
> and usbnet
> could then be removed and a change to use *_async() should be done?

That's right.  There are a few races you have to worry about (maybe
they're already taken into account -- I'm not familiar with these
drivers):

	What happens if a new URB has to be submitted at about the
	same time as an autosuspend occurs?

	What happens if you call one of the *_async() routines at the
	same time as some other CPU updates intf->pm_usage_count?

> I work with a module that have usb interfaces driven by above three 
> drivers so it
> could be a good testing case I guess.
> Generic solutions are the best so if this approach would work then of 
> course a
> change should be made I think. I have no time to test it in near time 
> though,
> perhaps later next week.

Okay, let me know how it turns out.

Alan Stern

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