Re: [RFC][PATCH] sched_clock_cpu()

From: Ingo Molnar
Date: Sun May 04 2008 - 05:00:55 EST



* David Miller <davem@xxxxxxxxxxxxx> wrote:

> > that wont work very well when sched_clock() is called from within
> > CONFIG_LOCK_STAT instrumentation. Does the patch below solve the
> > boot problems for you?
>
> Also, no platform can set HAVE_STABLE_CLOCK until we instantiate it in
> a Kconfig somewhere. I've choosen to do it in kernel/Kconfig.hz and
> here are the sparc/sparc64 bits as well, I've booted this up with
> Peter's patch on my 64-cpu niagara2 box and done some basic testing.

applied, thanks David.

right now this topic looks good in review and in testing but it is
stalled on a bug: in overnight testing it triggered an ftrace self-test
hang that i bisected down to that patch. While that doesnt affect
mainline it's something that shows that the new sched_clock() code is
not as widely usable as the old code - have to investigate that some
more.

> It would be nice if a powerpc person could test the trivial powerpc
> Kconfig patch.
>
> Possibly this should be HAVE_UNSTABLE_CLOCK, then only one platform
> needs to set it :-)

heh, indeed :)

Initially i thought that it's better to first be safe, but this really
will only affect x86 in practice, so ... i think we'll switch around the
flag, turning this into a no-effort thing for everything but x86.

Ingo
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