From 2be2a197ff6c3a659ab9285e1d88cbdc609ac6de Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 29 Feb 2024 15:23:36 +0100 Subject: [PATCH] sched/idle: Conditionally handle tick broadcast in default_idle_call() The x86 architecture has an idle routine for AMD CPUs which are affected by erratum 400. On the affected CPUs the local APIC timer stops in the C1E halt state. It therefore requires tick broadcasting. The invocation of tick_broadcast_enter()/exit() from this function violates the RCU constraints because it can end up in lockdep or tracing, which rightfully triggers a warning. tick_broadcast_enter()/exit() must be invoked before ct_cpuidle_enter() and after ct_cpuidle_exit() in default_idle_call(). Add a static branch conditional invocation of tick_broadcast_enter()/exit() into this function to allow X86 to replace the AMD specific idle code. It's guarded by a config switch which will be selected by x86. Otherwise it's a NOOP. Reported-by: Borislav Petkov Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20240229142248.266708822@linutronix.de --- include/linux/cpu.h | 2 ++ include/linux/tick.h | 3 +++ kernel/sched/idle.c | 21 +++++++++++++++++++++ kernel/time/Kconfig | 5 +++++ 4 files changed, 31 insertions(+) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index dcb89c9871640..715017d4432b5 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -196,6 +196,8 @@ void arch_cpu_idle(void); void arch_cpu_idle_prepare(void); void arch_cpu_idle_enter(void); void arch_cpu_idle_exit(void); +void arch_tick_broadcast_enter(void); +void arch_tick_broadcast_exit(void); void __noreturn arch_cpu_idle_dead(void); #ifdef CONFIG_ARCH_HAS_CPU_FINALIZE_INIT diff --git a/include/linux/tick.h b/include/linux/tick.h index 716d17f31c453..e134f286df8aa 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -12,6 +12,7 @@ #include #include #include +#include #ifdef CONFIG_GENERIC_CLOCKEVENTS extern void __init tick_init(void); @@ -63,6 +64,8 @@ enum tick_broadcast_state { TICK_BROADCAST_ENTER, }; +extern struct static_key_false arch_needs_tick_broadcast; + #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST extern void tick_broadcast_control(enum tick_broadcast_mode mode); #else diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 31231925f1ece..31ad811532957 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -81,6 +81,25 @@ void __weak arch_cpu_idle(void) cpu_idle_force_poll = 1; } +#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST_IDLE +DEFINE_STATIC_KEY_FALSE(arch_needs_tick_broadcast); + +static inline void cond_tick_broadcast_enter(void) +{ + if (static_branch_unlikely(&arch_needs_tick_broadcast)) + tick_broadcast_enter(); +} + +static inline void cond_tick_broadcast_exit(void) +{ + if (static_branch_unlikely(&arch_needs_tick_broadcast)) + tick_broadcast_exit(); +} +#else +static inline void cond_tick_broadcast_enter(void) { } +static inline void cond_tick_broadcast_exit(void) { } +#endif + /** * default_idle_call - Default CPU idle routine. * @@ -90,6 +109,7 @@ void __cpuidle default_idle_call(void) { instrumentation_begin(); if (!current_clr_polling_and_test()) { + cond_tick_broadcast_enter(); trace_cpu_idle(1, smp_processor_id()); stop_critical_timings(); @@ -99,6 +119,7 @@ void __cpuidle default_idle_call(void) start_critical_timings(); trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id()); + cond_tick_broadcast_exit(); } local_irq_enable(); instrumentation_end(); diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index bae8f11070bef..fc3b1a06c9816 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -39,6 +39,11 @@ config GENERIC_CLOCKEVENTS_BROADCAST bool depends on GENERIC_CLOCKEVENTS +# Handle broadcast in default_idle_call() +config GENERIC_CLOCKEVENTS_BROADCAST_IDLE + bool + depends on GENERIC_CLOCKEVENTS_BROADCAST + # Automatically adjust the min. reprogramming time for # clock event device config GENERIC_CLOCKEVENTS_MIN_ADJUST