Re: [PATCH 16/20] sched/idle: Use explicit broadcast oneshot control function

[Sudeep Holla]

Hi Rafael,

On 29/04/15 02:04, Rafael J. Wysocki wrote:
> On Wednesday, April 29, 2015 02:50:22 AM Rafael J. Wysocki wrote:

[...]

> > Below is the patch I came up with in the meantime.
> >
> > This moves the "switch to broadcast" timer logic into
> > cpuidle_enter_state() which allows tick_broadcast_exit() to be
> > called directly with interrupts disabled (as required), but
> > it also adds a fallback branch reflecting the 4.0 and earlier
> > behavior for idle states that enable interrupts on exit
> > from their ->enter callbacks.
> >
> > I'm not aware of any valid cases when CPUIDLE_FLAG_TIMER_STOP can be
> > set for such states, but people may try to add stuff like that in the
> > future, so it's better to catch that (hence the WARN_ON_ONCE) and do
> > our best to handle it gracefully anyway, IMO.
> >
> > The "if (entered_state == -EBUSY)" check is conservative.  It may
> > be better to do "if (entered_state < 0)" and fall back to the default
> > on all errors, but that's not what we do today (I guess the concern
> > would be "what if the state ->enter returns an error after entering
> > and exiting the idle state, in which case we may miss a wakeup event
> > if we fall back to the default").
>
> Actually, if my understanding of things is correct (the local clock event
> device cannot go away from under code executed with interrupts disabled
> on the local CPU), the simplified one below should be sufficient.

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

Regards,
Sudeep
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