From: "Petr Vandrovec" <VANDROVE@vc.cvut.cz>
To: Tim Schmielau <tim@physik3.uni-rostock.de>
Cc: <linux-kernel@vger.kernel.org>, J Sloan <jjs@lexus.com>,
adilger@turbolabs.com
Subject: Re: [Patch] Re: Nasty suprise with uptime
Date: Thu, 1 Nov 2001 09:02:44 MET-1 [thread overview]
Message-ID: <7EA9080566E@vcnet.vc.cvut.cz> (raw)
On 1 Nov 01 at 1:52, Tim Schmielau wrote:
> + static unsigned long jiffies_hi = 0;
> + static unsigned long jiffies_last = INITIAL_JIFFIES;
> + unsigned long jiffies_tmp;
> +
> + jiffies_tmp = jiffies; /* avoid races */
> + if (jiffies_tmp < jiffies_last) /* We have a wrap */
> + jiffies_hi++;
> + jiffies_last = jiffies_tmp;
There is very small race - if two processes will call get_jiffies64()
at same time, they can both happen to test jiffies_tmp < jiffies_last
with old jiffies_last - incrementing jiffies_hi twice :-( This race
window is only few microseconds every 497 days, but if we want
correct kernel...
Best regards,
Petr Vandrovec
vandrove@vc.cvut.cz
next reply other threads:[~2001-11-01 8:03 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-11-01 9:02 Petr Vandrovec [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-10-31 22:11 [Patch] Re: Nasty suprise with uptime Petr Vandrovec
2001-10-31 21:45 ` Andreas Dilger
2001-10-31 22:58 ` Tim Schmielau
2001-10-31 23:56 ` Andreas Dilger
2001-11-01 0:23 ` Tim Schmielau
2001-11-01 0:52 ` Tim Schmielau
2001-11-01 11:21 ` george anzinger
2001-11-01 11:40 ` Tim Schmielau
2001-11-02 0:28 ` Tim Schmielau
2001-11-02 1:23 ` Andreas Dilger
2001-11-02 9:10 ` Miquel van Smoorenburg
2001-11-02 17:18 ` Tim Schmielau
2001-11-02 18:48 ` Andreas Dilger
2001-11-01 16:35 ` vda
2001-11-01 15:34 ` Richard B. Johnson
2001-11-01 17:02 ` Benjamin LaHaise
2001-11-01 18:03 ` Richard B. Johnson
2001-11-01 18:34 ` Benjamin LaHaise
2001-11-02 14:46 ` vda
2001-11-01 17:29 ` george anzinger
[not found] <01103121070200.01262@nemo>
2001-10-31 19:26 ` Tim Schmielau
2001-10-31 19:52 ` Richard B. Johnson
2001-10-31 20:00 ` J Sloan
2001-10-31 20:20 ` Charles Cazabon
2001-10-31 20:33 ` Kurt Roeckx
2001-10-31 20:47 ` Tim Schmielau
2001-10-31 21:07 ` Andreas Dilger
2001-10-31 21:11 ` Richard B. Johnson
2001-11-01 16:09 ` vda
2001-10-31 11:35 Tim Schmielau
2001-10-31 15:39 ` vda
2001-10-31 14:31 ` Richard B. Johnson
2001-10-31 18:16 ` Tim Schmielau
2001-10-31 18:35 ` Tim Schmielau
2001-10-31 18:59 ` Andreas Dilger
2001-10-31 18:40 ` Andreas Dilger
2001-10-31 18:58 ` Gerhard Mack
2001-10-31 19:14 ` Richard B. Johnson
2001-10-31 20:11 ` Gerhard Mack
2001-10-31 20:39 ` Richard B. Johnson
2001-10-31 20:52 ` Andreas Dilger
2001-10-31 21:05 ` Tim Schmielau
2001-10-31 21:39 ` Andreas Dilger
2001-10-31 21:17 ` Richard B. Johnson
2001-11-01 7:45 ` Ville Herva
2001-10-31 19:06 ` george anzinger
2001-10-31 22:54 ` george anzinger
2001-11-04 18:31 ` Ton Hospel
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