linux-kernel - Re: Scheduler broken? sdhci issues with scheduling

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Message-ID: <20080301124203.GL24533@paranoidfreak.co.uk>
Date:	Sat, 1 Mar 2008 12:42:04 +0000
From:	Simon Huggins <huggie@...th.li>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Pierre Ossman <drzeus@...eus.cx>
Subject: Re: Scheduler broken? sdhci issues with scheduling

(please cc me)

On Fri, Feb 29, 2008 at 09:39:14PM +0100, Ingo Molnar wrote:
> * Simon Huggins <huggie@...th.li> wrote:
> > On Fri, Feb 29, 2008 at 02:34:33PM +0100, Ingo Molnar wrote:
> > > * Simon Huggins <huggie@...th.li> wrote:
> > > > [ Please Cc me on replies ]
> > > > I had a bug with sdhci which Pierre Ossman looked at for me.
> > > > In the end essentially the fix was to use HZ=1000 and nothing else. 
> > > > Pierre seemed to think that this was a bug in the scheduler.
> > > does the patch below help, even if you keep HZ=100? This doesnt look 
> > > like a scheduler issue, it's more of a timer/timing issue. Different HZ 
> > > means different msleep() results - and the mmc code does a loop of small 
> > > msleep delays.
> > Thanks for looking at it.
> > I did tests with 2.6.24.3 with HZ=1000 and HZ=100 and as expected the
> > latter didn't work.
[..]
> > That doesn't work.  I did a test with HZ=100 and this patch.  I've 
> > attached the log as patch1-log.

> > Anything else I can try?
> so neither precise, nor imprecise timings help??

I don't know.  I don't really understand the patches I applied I'm
afraid; I'm just reporting the results.

I've cc'd Pierre Ossman so he might have a look from the sdhci point of
view.

Pierre, the thread starts here:
http://lkml.org/lkml/2008/2/29/118

Simon.

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