diff options
| -rw-r--r-- | include/linux/perf_event.h | 6 | ||||
| -rw-r--r-- | kernel/events/core.c | 49 |
2 files changed, 44 insertions, 11 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 3915661..f5c5a3f 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -906,7 +906,7 @@ perf_sw_event_sched(u32 event_id, u64 nr, u64 addr) } } -extern struct static_key_deferred perf_sched_events; +extern struct static_key_false perf_sched_events; static __always_inline bool perf_sw_migrate_enabled(void) @@ -925,7 +925,7 @@ static inline void perf_event_task_migrate(struct task_struct *task) static inline void perf_event_task_sched_in(struct task_struct *prev, struct task_struct *task) { - if (static_key_false(&perf_sched_events.key)) + if (static_branch_unlikely(&perf_sched_events)) __perf_event_task_sched_in(prev, task); if (perf_sw_migrate_enabled() && task->sched_migrated) { @@ -942,7 +942,7 @@ static inline void perf_event_task_sched_out(struct task_struct *prev, { perf_sw_event_sched(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 0); - if (static_key_false(&perf_sched_events.key)) + if (static_branch_unlikely(&perf_sched_events)) __perf_event_task_sched_out(prev, next); } diff --git a/kernel/events/core.c b/kernel/events/core.c index 92d6999..ea064ca 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -321,7 +321,13 @@ enum event_type_t { * perf_sched_events : >0 events exist * perf_cgroup_events: >0 per-cpu cgroup events exist on this cpu */ -struct static_key_deferred perf_sched_events __read_mostly; + +static void perf_sched_delayed(struct work_struct *work); +DEFINE_STATIC_KEY_FALSE(perf_sched_events); +static DECLARE_DELAYED_WORK(perf_sched_work, perf_sched_delayed); +static DEFINE_MUTEX(perf_sched_mutex); +static atomic_t perf_sched_count; + static DEFINE_PER_CPU(atomic_t, perf_cgroup_events); static DEFINE_PER_CPU(int, perf_sched_cb_usages); @@ -3536,12 +3542,22 @@ static void unaccount_event(struct perf_event *event) if (has_branch_stack(event)) dec = true; - if (dec) - static_key_slow_dec_deferred(&perf_sched_events); + if (dec) { + if (!atomic_add_unless(&perf_sched_count, -1, 1)) + schedule_delayed_work(&perf_sched_work, HZ); + } unaccount_event_cpu(event, event->cpu); } +static void perf_sched_delayed(struct work_struct *work) +{ + mutex_lock(&perf_sched_mutex); + if (atomic_dec_and_test(&perf_sched_count)) + static_branch_disable(&perf_sched_events); + mutex_unlock(&perf_sched_mutex); +} + /* * The following implement mutual exclusion of events on "exclusive" pmus * (PERF_PMU_CAP_EXCLUSIVE). Such pmus can only have one event scheduled @@ -7780,8 +7796,28 @@ static void account_event(struct perf_event *event) if (is_cgroup_event(event)) inc = true; - if (inc) - static_key_slow_inc(&perf_sched_events.key); + if (inc) { + if (atomic_inc_not_zero(&perf_sched_count)) + goto enabled; + + mutex_lock(&perf_sched_mutex); + if (!atomic_read(&perf_sched_count)) { + static_branch_enable(&perf_sched_events); + /* + * Guarantee that all CPUs observe they key change and + * call the perf scheduling hooks before proceeding to + * install events that need them. + */ + synchronize_sched(); + } + /* + * Now that we have waited for the sync_sched(), allow further + * increments to by-pass the mutex. + */ + atomic_inc(&perf_sched_count); + mutex_unlock(&perf_sched_mutex); + } +enabled: account_event_cpu(event, event->cpu); } @@ -9344,9 +9380,6 @@ void __init perf_event_init(void) ret = init_hw_breakpoint(); WARN(ret, "hw_breakpoint initialization failed with: %d", ret); - /* do not patch jump label more than once per second */ - jump_label_rate_limit(&perf_sched_events, HZ); - /* * Build time assertion that we keep the data_head at the intended * location. IOW, validation we got the __reserved[] size right. |