Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 23 Nov 2020 15:54:43 +0100 | Subject | Re: [PATCH 2/2] intel_idle: Fix intel_idle() vs tracing |
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On Mon, Nov 23, 2020 at 3:35 PM Peter Zijlstra <peterz@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 <peterz@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) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@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++; > } >
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