On Mon, Nov 23, 2020 at 3:35 PM Peter Zijlstra <pet...@infradead.org> wrote:
>
> On Mon, Nov 23, 2020 at 02:54:47PM +0100, Rafael J. Wysocki wrote:
>
> > intel_idle_init_cstates_acpi() needs to be updated too as it doesn't
> > pick up the flags automatically.
>
> Ooh, it has two different state init routines :-/, sorry I missed that.
> See below.
>
> > It looks like CPUIDLE_FLAG_RCU_IDLE needs to be copied too.
>
> I might need more clue again; processor_idle() needs this because it
> calls into ACPI (acpi_idle_enter_bm()) for that BM crud. I didn't find
> anything like that here.
>
>
> ---
> Subject: intel_idle: Fix intel_idle() vs tracing
> From: Peter Zijlstra <pet...@infradead.org>
> Date: Fri Nov 20 11:28:35 CET 2020
>
> 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>
Acked-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
with a very minor nit below.
> ---
> drivers/idle/intel_idle.c | 40 +++++++++++++++++++++++-----------------
> 1 file changed, 23 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;
> }
>
> @@ -1227,6 +1210,23 @@ static bool __init intel_idle_acpi_cst_e
> return false;
> }
>
> +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;
The above can be written as
return !!((eax >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK);
> +}
> +
> static void __init intel_idle_init_cstates_acpi(struct cpuidle_driver *drv)
> {
> int cstate, limit = min_t(int, CPUIDLE_STATE_MAX,
> acpi_state_table.count);
> @@ -1269,6 +1269,9 @@ static void __init intel_idle_init_cstat
> if (disabled_states_mask & BIT(cstate))
> state->flags |= CPUIDLE_FLAG_OFF;
>
> + if (intel_idle_state_needs_timer_stop(state))
> + state->flags |= CPUIDLE_FLAG_TIMER_STOP;
> +
> state->enter = intel_idle;
> state->enter_s2idle = intel_idle_s2idle;
> }
> @@ -1507,6 +1510,9 @@ 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++;
> }
>
