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SubjectRe: Scheduler broken? sdhci issues with scheduling

* Simon Huggins <huggie@earth.li> wrote:

> Hi Ingo,
>
> (please cc me again)
>
> On Fri, Feb 29, 2008 at 02:34:33PM +0100, Ingo Molnar wrote:
> > * Simon Huggins <huggie@earth.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.
>
> > -------------->
> > ---
> > drivers/mmc/core/core.h | 7 +------
> > 1 file changed, 1 insertion(+), 6 deletions(-)
>
> > Index: linux/drivers/mmc/core/core.h
> > ===================================================================
> > --- linux.orig/drivers/mmc/core/core.h
> > +++ linux/drivers/mmc/core/core.h
> > @@ -36,12 +36,7 @@ void mmc_set_timing(struct mmc_host *hos
>
> > static inline void mmc_delay(unsigned int ms)
> > {
> > - if (ms < 1000 / HZ) {
> > - cond_resched();
> > - mdelay(ms);
> > - } else {
> > - msleep(ms);
> > - }
> > + mdelay(ms);
> > }
>
> > void mmc_rescan(struct work_struct *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??

Ingo


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