Date: Tue, 7 Oct 2008 20:02:13 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Elias Oltmanns <eo@nebensachen.de>
cc: Jiri Slaby <jirislaby@gmail.com>, linux-wireless@vger.kernel.org
Subject: Re: ath5k: kernel timing screwed - due to unserialised register
 access?
In-Reply-To: <87skr8h1de.fsf@denkblock.local>
Message-ID: <alpine.LFD.2.00.0810071946460.3166@apollo> (sfid-20081007_200230_653221_9801757E)
References: <87k5cm3ee2.fsf@denkblock.local> <alpine.LFD.2.00.0810052354000.3398@apollo> <87d4id3jmr.fsf@denkblock.local> <alpine.LFD.2.00.0810061614490.3166@apollo> <87skr8h1de.fsf@denkblock.local>
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On Tue, 7 Oct 2008, Elias Oltmanns wrote:
> Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Mon, 6 Oct 2008, Elias Oltmanns wrote:
> >> Make sure that event1 is the right device. chktimer usually reports
> >> several premature timer expiries in less than a minute.
> [...]
> > Your measuring method is wrong. You really want to measure the delta
> > of the timer events in the kernel via ktime_get(), not the delta of
> > something else in userspace.
> 
> Alright, here is a stripped down version of the test case. This time,
> you only need to load the timer-test module and start up the ath5k
> interface. The glitch is triggered slightly less reliably, but I can

-ENOATH5KHARDWARE

> still easily verify that the problem is present when running 2.6.27-rc9
> on my system.

Hmm. Can you please add some real info to the printk :)

> +	if (timespec_to_ns(&diff) < TSTM_THRESH)
> +		printk(KERN_INFO "Timer expired prematurely.\n");

e.g.:

  		printk(KERN_INFO "b: %6ld.%09ld n: %6ld.09ld e: %lu j: %lu\n",
			before.tv_sec, before.tv_nsec, now.tv_sec, now.tv_nsec,
			tstm_timer.expires, jiffies);

Does this happen w/o the ath5k driver as well ?

Thanks,

	tglx