Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 23 Nov 2020 14:54:47 +0100 | Subject | Re: [PATCH 2/2] intel_idle: Fix intel_idle() vs tracing |
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On Mon, Nov 23, 2020 at 2:46 PM Peter Zijlstra <peterz@infradead.org> wrote: > > 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 <peterz@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) <peterz@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?
Nope.
intel_idle_init_cstates_acpi() needs to be updated too as it doesn't pick up the flags automatically. It looks like CPUIDLE_FLAG_RCU_IDLE needs to be copied too.
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