On Mon, 2005-11-28 at 19:02 -0800, Andrew Morton wrote:
> Steven Rostedt <[email protected]> wrote:
> >
> > This patch creates a directory in /sys/kernel called idle.
> >
>
> At no point do you appear to explain _why_ the kernel needs this feature?
Sorry about that. This originally came up when we had problems with the
AMD64 x2 in the -rt patch. It was noted that the TSCs would get very
far out of sync and cause problems. The way to solve this was to set
idle=poll. The original patch I sent was to allow the user to change to
idle=poll dynamically. This way they could switch to the poll_idle and
run there tests (requiring tsc not to drift) and then switch back to the
default idle to save on electricity.
Note: It's been stated that the tsc drift can cause problems with the
vanilla kernel too.
Ingo asked if I could make this more robust and not dependent on
idle_poll.
Maybe Ingo can give a better explanation?
>
> > ...
> > - pm_idle = pm_idle_save;
> > + int tries = 0;
> > + int ret;
> > + set_idle(NULL);
> > + do {
> > + if ((ret = unregister_idle(PM_IDLE_NAME)) == 0)
> > + break;
> > + /*
> > + * for some reason the idle function is being used.
> > + * Wait a little and then try again.
> > + */
> > + if (ret == -EINVAL) {
> > + printk(KERN_WARNING
> > + "ACPI idle function never registered?\n");
> > + break;
> > + }
> > + yield();
> > + } while (tries++ < 10);
>
> The use of yield() could be problematic - its semantics are rather
> ill-defined. Maybe msleep(1) or something?
>
> What's this loop here for anyway? Looks kludgy.
Oops! That was required by some other garbage that I had earlier. I
cleaned up the patch some more, and this is no longer required. (will
remove).
>
> > + if (tries > 10) {
> > + printk(KERN_WARNING
> > + "Unable to unresgister ACPI idle function\n");
>
> tpyo
Will fix.
>
> > + memset(&idle_kobj, 0, sizeof(idle_kobj));
>
> There are several memsets of statically allocated structures which are
> already all-zero.
>
:) I'm really paranoid! OK, I always like to do a memset even when it's
not needed. I'll purge them too.
Thanks for having a look.
-- Steve
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