RFC: 405LP sleep

Hollis Blanchard hollis at austin.ibm.com
Sat Dec 21 10:31:14 EST 2002

On Thu, 2002-12-19 at 15:36, Todd Poynor wrote:
> Suggest more unique names for these globals.

Well, how about making them static? :)

> +       jiffies += rtc_secs_elapsed * HZ;
> If jiffies is jumped forward then can kernel events (such as those
> waiting on a kernel timer) be missed?

I certainly *hope* the check is >= rather than == ... :)

> Whether or not timer queues et al
> are processed on wakeup, not sure if it's harmful to update the "kernel
> time" when the kernel has done nothing during the sleep interval, maybe
> causing various timeouts.  Has this been tried with applications like X
> running and verified not to kill apps on wakeup?

I have not run anything interesting like X, no.

> Matt Locke and I have been discussing whether it's best to update wall
> clock time but leave jiffies alone, since "kernel time" did not advance
> during the sleep interval.  It's a little worrisome: the kernel advances
> time by 10ms for its own operations, but wallclock time (xtime and RTC)
> jumps forward 10 minutes.  We've tried this a little bit on a TI OMAP
> and haven't seen anything die so far, but I imagine there'll be some
> application that isn't happy about the situation no matter what choice
> is made.

Before posting I had tried commenting out the jiffies update and it
seemed to run ok both ways. I decided to leave it in though to preserve
the reality of time passing as much as possible.
arch/arm/mach-sa1100/pm.c seems to only update xtime.tv_sec. I'm hoping
Someone Who Knows will comment one way or the other here...

The updated patch, with many cleanups and one important bugfix, has been
posted to http://penguinppc.org/~hollis/405LP-sleep.diff. Aside from the
remaining get_pteptr problem, I think the code is ready to be checked
in. If anyone disagrees please let me know. :)

PowerPC Linux
IBM Linux Technology Center

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