Messages in this thread Patch in this message | | | Date | Mon, 23 Nov 2020 15:35:10 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/2] intel_idle: Fix intel_idle() vs tracing |
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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> --- 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; +} + 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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