linux-kernel - Re: ohci : strange looking use of round_jiffies

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Message-ID: <a340dd0e0803261106v67bbecdaie8a3f52b47e2c84a@mail.gmail.com>
Date:	Wed, 26 Mar 2008 14:06:49 -0400
From:	"Mike Nuss" <mikenuss@...il.com>
To:	"Richard Kennedy" <richard@....demon.co.uk>
Cc:	"Alan Stern" <stern@...land.harvard.edu>,
	dbrownell@...rs.sourceforge.net,
	linux-usb <linux-usb@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: ohci : strange looking use of round_jiffies_relative. possible bug ?

On Wed, Mar 26, 2008 at 11:46 AM, Richard Kennedy
<richard@....demon.co.uk> wrote:
>
>  On Wed, 2008-03-26 at 11:37 -0400, Alan Stern wrote:
>  > On Wed, 26 Mar 2008, Richard Kennedy wrote:
>  >
>  > > I was looking at the uses of round_jiffies and noticed that the ohci
>  > > unlink_watchdog_func() calls
>  > > mod_timer(&ohci->unlink_watchdog, round_jiffies_relative(HZ));
>  > >
>  > > Which looks a bit strange as it will set the timer to 0 <= t < HZ.
>  > > Reading the comments I think that is really is expecting to setup timer
>  > > to (now + 1s)
>  > >
>  > > mod_timer(&ohci->unlink_watchdog, round_jiffies(jiffies + HZ));
>  > >
>  > > If this is not true then perhaps it needs a comment to explain what it
>  > > _is_ trying to do, because it's got me baffled ;)

Yes, my intent there was a roughly 1 second delay. You're correct, it's wrong.

>  > I'd say it's a bug.  Or rather a pair of bugs, since that mod_timer()
>  > call appears in two places.

Yup.

Mike
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