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Date: Wed, 29 May 2013 16:01:50 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Bart Van Assche <bart.vanassche@...il.com> Cc: 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>, Joe Perches <joe@...ches.com> Subject: Re: [PATCH] timer: Fix jiffies wrap behavior of round_jiffies*() On Tue, 21 May 2013 20:43:50 +0200 Bart Van Assche <bart.vanassche@...il.com> wrote: > Make sure that the round_jiffies*() functions return a time that is > in the future when the jiffies counter is about to wrap. Actually "when the jiffies counter has recently wrapped". I assume this was found by inspection? > @@ -149,9 +149,7 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu, > /* now that we have rounded, subtract the extra skew again */ > j -= cpu * 3; > - if (j <= jiffies) /* rounding ate our timeout entirely; */ This used to be a very common bug - we've weeded out many instances but I'm sure more still remain. We could perhaps have a checkpatch rule which looks for comparisons against jiffes (and any other time-measuring variables we can detect) and tells people to use time_after() and friends, or time_is_*_jiffies(). > - return original; > - return j; > + return time_is_after_jiffies(j) ? j : original; > } Your email client mangles patches, btw. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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