On Mon, Nov 23, 2020 at 11:26:39AM +0100, Rafael J. Wysocki wrote:
> On Fri, Nov 20, 2020 at 12:50 PM Peter Zijlstra <pet...@infradead.org> wrote:
> >
> > cpuidle->enter() callbacks should not call into tracing because RCU
> > has already been disabled. Instead of doing the broadcast thing
> > itself, simply advertise to the cpuidle core that those states stop
> > the timer.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> > ---
> > drivers/idle/intel_idle.c | 37 ++++++++++++++++++++-----------------
> > 1 file changed, 20 insertions(+), 17 deletions(-)
> >
> > --- a/drivers/idle/intel_idle.c
> > +++ b/drivers/idle/intel_idle.c
> > @@ -126,26 +126,9 @@ static __cpuidle int intel_idle(struct c
> > struct cpuidle_state *state = &drv->states[index];
> > unsigned long eax = flg2MWAIT(state->flags);
> > unsigned long ecx = 1; /* break on interrupt flag */
> > - bool tick;
> > -
> > - if (!static_cpu_has(X86_FEATURE_ARAT)) {
> > - /*
> > - * Switch over to one-shot tick broadcast if the target
> > C-state
> > - * is deeper than C1.
> > - */
> > - if ((eax >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) {
> > - tick = true;
> > - tick_broadcast_enter();
> > - } else {
> > - tick = false;
> > - }
> > - }
> >
> > mwait_idle_with_hints(eax, ecx);
> >
> > - if (!static_cpu_has(X86_FEATURE_ARAT) && tick)
> > - tick_broadcast_exit();
> > -
> > return index;
> > }
> >
> > @@ -1460,6 +1443,23 @@ static bool __init intel_idle_verify_cst
> > return true;
> > }
> >
> > +static bool __init intel_idle_state_needs_timer_stop(struct cpuidle_state
> > *state)
> > +{
> > + unsigned long eax = flg2MWAIT(state->flags);
> > +
> > + if (boot_cpu_has(X86_FEATURE_ARAT))
> > + return false;
> > +
> > + /*
> > + * Switch over to one-shot tick broadcast if the target C-state
> > + * is deeper than C1.
> > + */
> > + if ((eax >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK)
> > + return true;
> > +
> > + return false;
> > +}
> > +
> > static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv)
> > {
> > int cstate;
> > @@ -1507,6 +1507,9 @@ static void __init intel_idle_init_cstat
> > !(cpuidle_state_table[cstate].flags &
> > CPUIDLE_FLAG_ALWAYS_ENABLE)))
> > drv->states[drv->state_count].flags |=
> > CPUIDLE_FLAG_OFF;
> >
> > + if
> > (intel_idle_state_needs_timer_stop(&drv->states[drv->state_count]))
> > + drv->states[drv->state_count].flags |=
> > CPUIDLE_FLAG_TIMER_STOP;
> > +
> > drv->state_count++;
> > }
>
> This doesn't cover the ACPI case AFAICS.
aa6b43d57f99 ("ACPI: processor: Use CPUIDLE_FLAG_TIMER_STOP")
did that, no?
