Re: Scheduler broken? sdhci issues with scheduling


* Simon Huggins <huggie@xxxxxxxx> wrote:

Hi Ingo,

(please cc me again)

On Fri, Feb 29, 2008 at 02:34:33PM +0100, Ingo Molnar wrote:
* Simon Huggins <huggie@xxxxxxxx> 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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