linux-kernel - Re: [PATCH] timer: Fix jiffies wrap behavior of round

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Message-ID: <1369871306.22004.126.camel@joe-AO722>
Date:	Wed, 29 May 2013 16:48:26 -0700
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Bart Van Assche <bart.vanassche@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] timer: Fix jiffies wrap behavior of round_jiffies*()

On Wed, 2013-05-29 at 16:38 -0700, Andrew Morton wrote:
> On Wed, 29 May 2013 16:17:47 -0700 Joe Perches <joe@...ches.com> wrote:
> 
> > >   We could perhaps have a checkpatch rule
> > > which looks for comparisons against jiffes (and any other
> > > time-measuring variables we can detect)
> > 
> > other variables like?
> 
> Grepping for time_after finds a bunch.  There's no real pattern to it though.

Yup, that's the problem.
Thought I'd ask what I was missing though.

No variable really stands out as testable other
than jiffies.

I added this to my local queue and I'll send it later.

# check for comparisons of jiffies
		if ($line =~ /\bif\s*\((\s*jiffies\s*[\<\>]|.*[\<\>]=?\s*jiffies\b)/) {
			WARN("JIFFIES_COMPARISON",
			     "Comparing jiffies is almost always wrong; prefer time_after, time_before and friends\n" . $herecurr);
		}


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