linux-kernel - Re: PROBLEM: CONFIG_NO_HZ could cause software timeouts

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Message-ID: <20090906052717.GC1324@ucw.cz>
Date:	Sun, 6 Sep 2009 07:27:17 +0200
From:	Pavel Machek <pavel@....cz>
To:	Norbert van Bolhuis <nvbolhuis@...valley.nl>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: PROBLEM: CONFIG_NO_HZ could cause software timeouts

On Thu 2009-09-03 12:50:12, Norbert van Bolhuis wrote:
>
> The problem occurs when e.g. drivers use time_after(jiffes, timeout).
>
> CONFIG_NO_HZ could make jiffies advance by more than 1.
> This is done by: tick_nohz_update_jiffies->tick_do_update_jiffies64->do_timer

jiffies really should be up-to-date as long as you are running
anything else than idle loop. If not, that's a bug ... and nasty one.

-- 
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