linux-kernel - Re: [PATCH] Moving spinlock to struct usb

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Message-ID: <9f29ca150801272020t2ced46b6ka8e7890dfbe1e1a8@mail.gmail.com>
Date:	Mon, 28 Jan 2008 09:50:36 +0530
From:	"Romit Dasgupta" <romlinux@...il.com>
To:	"David Brownell" <david-b@...bell.net>
Cc:	greg@...ah.com, stern@...land.harvard.edu,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Moving spinlock to struct usb_hcd

Hi,
                 Should I go ahead and submit the patch with the usual
"signed-off" thingie? Or is it totally useless patch that is going to
be ignored?

Thanks,
-Romit


On Jan 26, 2008 9:06 PM, Romit Dasgupta <romlinux@...il.com> wrote:
> >
> >
> > Looking at how this lock is used, contention doesn't look likely
> > to be an issue.  It's never held for long ...
> yes in the general case but in usb_hcd_flush_endpoint routine it seems
> to be held for longer than other routines. I agree that
> usb_hcd_flush_endpoint is an infrequently called routine. Normal
> systems dont have too many HCs. My computer shows 1 EHCI and 3 OHCIs
> so I guess when I connect high speed devices there are less chances of
> contention. With more HC this lock might be contended for.
> Nevertheless, the right place for the lock seems to be inside usb_hcd.
> What do you think?
>
> >
> >
> > Do you have any proof that contention is an actual problem?
> > Because otherwise I see no benefit to such a change.
> >
>
> I will try to see what I can find with /proc/lock_stat.
>
> Thanks,
> -Romit
>
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