linux-kernel - Re: Wireless IBSS on Linux-2.6.34 broken by commit 3bbb9ec946428b96657126768f65487a48dd090c

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Message-ID: <alpine.LFD.2.00.1005252034430.2948@localhost.localdomain>
Date:	Tue, 25 May 2010 20:37:40 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Jeff Chua <jeff.chua.linux@...il.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	"johnstul@...ibm.com" <johnstul@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Intel Linux Wireless <ilw@...ux.intel.com>,
	"John W. Linville" <linville@...driver.com>,
	Frans Pop <elendil@...net.nl>,
	"Chatre, Reinette" <reinette.chatre@...el.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Wireless IBSS on Linux-2.6.34 broken by commit
 3bbb9ec946428b96657126768f65487a48dd090c

On Mon, 24 May 2010, Linus Torvalds wrote:
> 
> On Mon, 24 May 2010, Jeff Chua wrote:
> > 
> > -	expires_limit = expires + timer->slack;
> > +	expires_limit = expires;
> > 
> > -	if (timer->slack < 0) /* auto slack: use 0.4% */
> > +	if (timer->slack > -1)
> > +		expires_limit = expires + timer->slack;
> > +	else if (time_after(expires, jiffies)) /* auto slack: use 0.4% */
> >  		expires_limit = expires + (expires - jiffies)/256;
> 
> Please don't reload 'jiffies' twice. It's volatile, and the compiler will 
> do a crap job of it. 

Grr, it's even worse. If jiffies increment between the time_after()
check and (expires - jiffies) we might run into the same problem as
before. Sigh, did not notice when I picked it up. ENOTENOUGHCOFFEE.
 
> Also, '0' is a normal number, but '-1' is a rather odd value. Please just 
> test for non-negative by doing ">= 0" rather than "> -1"

Will fix, thanks,

     tglx
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