On 09/12/2013 10:30 PM, Thomas Gleixner wrote:

On Thu, 12 Sep 2013, Soren Brinkmann wrote:

quoted

From: Stephen Boyd <redacted>

On most ARM systems the per-cpu clockevents are truly per-cpu in
the sense that they can't be controlled on any other CPU besides
the CPU that they interrupt. If one of these clockevents were to
become a broadcast source we will run into a lot of trouble
because the broadcast source is enabled on the first CPU to go
into deep idle (if that CPU suffers from FEAT_C3_STOP) and that
could be a different CPU than what the clockevent is interrupting
(or even worse the CPU that the clockevent interrupts could be
offline).

Theoretically it's possible to support per-cpu clockevents as the
broadcast source but so far we haven't needed this and supporting
it is rather complicated. Let's just deny the possibility for now
until this becomes a reality (let's hope it never does!).

Well, we can't do it this way. There are globally accessible clock
event devices which deliver only to cpu0. So the mask check might be
causing failure here.

Just add a feature flag CLOCK_EVT_FEAT_PERCPU to the clock event
device and check for it.

It sounds probably more understandable than dealing with the cpumasks.

I am wondering if this is semantically opposed to
http://lwn.net/Articles/566270/ ?

[PATCH V3 0/6] cpuidle/ppc: Enable broadcast support for deep idle states

  -- Daniel

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