From: Thomas Gleixner Actually a nice symmetric startup/teardown pair which fits properly into the state machine concept. In the long run we should be able to invoke the startup callback for the boot CPU via the state machine and get rid of the init function which invokes it on the boot CPU. Note: This comes actually before the perf hardware callbacks. In the notifier model the hardware callbacks have a higher priority than the core callback. But that's solely for CPU offline so that hardware migration of events happens before the core is notified about the outgoing CPU. With the symetric state array model we have the following ordering: UP: core -> hardware DOWN: hardware -> core Signed-off-by: Thomas Gleixner Reviewed-by: Sebastian Siewior Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rasmus Villemoes Signed-off-by: Anna-Maria Gleixner --- include/linux/cpuhotplug.h | 2 + include/linux/perf_event.h | 9 +++++++ kernel/cpu.c | 11 ++++++++ kernel/events/core.c | 56 ++++++++------------------------------------- 4 files changed, 32 insertions(+), 46 deletions(-) --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -4,6 +4,7 @@ enum cpuhp_state { CPUHP_OFFLINE, CPUHP_CREATE_THREADS, + CPUHP_PERF_PREPARE, CPUHP_NOTIFY_PREPARE, CPUHP_BRINGUP_CPU, CPUHP_AP_IDLE_DEAD, @@ -22,6 +23,7 @@ enum cpuhp_state { CPUHP_AP_ONLINE_IDLE, CPUHP_AP_SMPBOOT_THREADS, CPUHP_AP_X86_VDSO_VMA_ONLINE, + CPUHP_AP_PERF_ONLINE, CPUHP_AP_NOTIFY_ONLINE, CPUHP_AP_ONLINE_DYN, CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30, --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1354,4 +1354,13 @@ static ssize_t \ \ static struct device_attribute format_attr_##_name = __ATTR_RO(_name) +/* Performance counter hotplug functions */ +#ifdef CONFIG_PERF_EVENTS +int perf_event_init_cpu(unsigned int cpu); +int perf_event_exit_cpu(unsigned int cpu); +#else +#define perf_event_init_cpu NULL +#define perf_event_exit_cpu NULL +#endif + #endif /* _LINUX_PERF_EVENT_H */ --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1180,6 +1180,11 @@ static struct cpuhp_step cpuhp_bp_states .teardown = NULL, .cant_stop = true, }, + [CPUHP_PERF_PREPARE] = { + .name = "perf prepare", + .startup = perf_event_init_cpu, + .teardown = perf_event_exit_cpu, + }, /* * Preparatory and dead notifiers. Will be replaced once the notifiers * are converted to states. @@ -1255,6 +1260,12 @@ static struct cpuhp_step cpuhp_ap_states .startup = smpboot_unpark_threads, .teardown = NULL, }, + [CPUHP_AP_PERF_ONLINE] = { + .name = "perf online", + .startup = perf_event_init_cpu, + .teardown = perf_event_exit_cpu, + }, + /* * Online/down_prepare notifiers. Will be removed once the notifiers * are converted to states. --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10255,7 +10255,7 @@ static void __init perf_event_init_all_c } } -static void perf_event_init_cpu(int cpu) +int perf_event_init_cpu(unsigned int cpu) { struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu); @@ -10268,6 +10268,7 @@ static void perf_event_init_cpu(int cpu) rcu_assign_pointer(swhash->swevent_hlist, hlist); } mutex_unlock(&swhash->hlist_mutex); + return 0; } #if defined CONFIG_HOTPLUG_CPU || defined CONFIG_KEXEC_CORE @@ -10299,14 +10300,17 @@ static void perf_event_exit_cpu_context( } srcu_read_unlock(&pmus_srcu, idx); } +#else + +static void perf_event_exit_cpu_context(int cpu) { } + +#endif -static void perf_event_exit_cpu(int cpu) +int perf_event_exit_cpu(unsigned int cpu) { perf_event_exit_cpu_context(cpu); + return 0; } -#else -static inline void perf_event_exit_cpu(int cpu) { } -#endif static int perf_reboot(struct notifier_block *notifier, unsigned long val, void *v) @@ -10328,46 +10332,6 @@ static struct notifier_block perf_reboot .priority = INT_MIN, }; -static int -perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) -{ - unsigned int cpu = (long)hcpu; - - switch (action & ~CPU_TASKS_FROZEN) { - - case CPU_UP_PREPARE: - /* - * This must be done before the CPU comes alive, because the - * moment we can run tasks we can encounter (software) events. - * - * Specifically, someone can have inherited events on kthreadd - * or a pre-existing worker thread that gets re-bound. - */ - perf_event_init_cpu(cpu); - break; - - case CPU_DOWN_PREPARE: - /* - * This must be done before the CPU dies because after that an - * active event might want to IPI the CPU and that'll not work - * so great for dead CPUs. - * - * XXX smp_call_function_single() return -ENXIO without a warn - * so we could possibly deal with this. - * - * This is safe against new events arriving because - * sys_perf_event_open() serializes against hotplug using - * get_online_cpus(). - */ - perf_event_exit_cpu(cpu); - break; - default: - break; - } - - return NOTIFY_OK; -} - void __init perf_event_init(void) { int ret; @@ -10380,7 +10344,7 @@ void __init perf_event_init(void) perf_pmu_register(&perf_cpu_clock, NULL, -1); perf_pmu_register(&perf_task_clock, NULL, -1); perf_tp_register(); - perf_cpu_notifier(perf_cpu_notify); + perf_event_init_cpu(smp_processor_id()); register_reboot_notifier(&perf_reboot_notifier); ret = init_hw_breakpoint();