Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast_enter() failures

From: Sudeep Holla
Date: Mon May 11 2015 - 11:13:47 EST

On 10/05/15 00:15, Rafael J. Wysocki wrote:
On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote:
On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote:
On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote:
Hi Rafael,

On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote:


+ /* Take note of the planned idle state. */
+ idle_set_state(smp_processor_id(), target_state);

And I wouldn't do this either.

The behavior here is pretty much as though the driver demoted the state chosen
by the governor and we don't call idle_set_state() again in those cases.

Why is this wrong?

It is not "wrong", but incomplete, because demotions done by the cpuidle driver
should also be taken into account in the same way.

But I'm seeing that the recent patch of mine that made cpuidle_enter_state()
call default_idle_call() was a mistake, because it might confuse find_idlest_cpu()
significantly as to what state the CPU is in. I'll drop that one for now.

OK, done.

So after I've dropped it I think we need to do three things:
(1) Move the idle_set_state() calls to cpuidle_enter_state().
(2) Make cpuidle_enter_state() call default_idle_call() again, but this time
do that *before* it has called idle_set_state() for target_state.
(3) Introduce demotion as per my last patch.

Let me cut patches for that.

Done as per the above and the patches follow in replies to this messge.

All on top of the current linux-next branch of the linux-pm.git tree.

Tested on ARM Vexpress platforms with one of the CPU in broadcast mode
and also with broadcast timer. So, you can add:

Tested-by: Sudeep Holla <sudeep.holla@xxxxxxx>

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