From f91fd73b8982db34560bf3fe6da9fdf9a42901a9 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 9 Jun 2011 14:38:33 -0400 Subject: [PATCH] Handle perf counter's inability to setup counters before cpu is brought online Signed-off-by: Mathieu Desnoyers --- lttng-context-perf-counters.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/lttng-context-perf-counters.c b/lttng-context-perf-counters.c index 2e194991..56e0d250 100644 --- a/lttng-context-perf-counters.c +++ b/lttng-context-perf-counters.c @@ -36,8 +36,19 @@ void perf_counter_record(struct lttng_ctx_field *field, uint64_t value; event = field->u.perf_counter.e[ctx->cpu]; - event->pmu->read(event); - value = local64_read(&event->count); + if (likely(event)) { + event->pmu->read(event); + value = local64_read(&event->count); + } else { + /* + * Perf chooses not to be clever and not to support enabling a + * perf counter before the cpu is brought up. Therefore, we need + * to support having events coming (e.g. scheduler events) + * before the counter is setup. Write an arbitrary 0 in this + * case. + */ + value = 0; + } lib_ring_buffer_align_ctx(ctx, ltt_alignof(value)); chan->ops->event_write(ctx, &value, sizeof(value)); } @@ -90,7 +101,7 @@ int __cpuinit lttng_perf_counter_cpu_hp_callback(struct notifier_block *nb, container_of(nb, struct lttng_ctx_field, u.perf_counter.nb); struct perf_event **events = field->u.perf_counter.e; struct perf_event_attr *attr = field->u.perf_counter.attr; - + struct perf_event *pevent; if (!field->u.perf_counter.hp_enable) return NOTIFY_OK; @@ -98,16 +109,21 @@ int __cpuinit lttng_perf_counter_cpu_hp_callback(struct notifier_block *nb, switch (action) { case CPU_ONLINE: case CPU_ONLINE_FROZEN: - events[cpu] = perf_event_create_kernel_counter(attr, + pevent = perf_event_create_kernel_counter(attr, cpu, NULL, overflow_callback); - if (!events[cpu]) + if (!pevent) return NOTIFY_BAD; + barrier(); /* Create perf counter before setting event */ + events[cpu] = pevent; break; case CPU_UP_CANCELED: case CPU_UP_CANCELED_FROZEN: case CPU_DEAD: case CPU_DEAD_FROZEN: - perf_event_release_kernel(events[cpu]); + pevent = events[cpu]; + events[cpu] = NULL; + barrier(); /* NULLify event before perf counter teardown */ + perf_event_release_kernel(pevent); break; } return NOTIFY_OK; -- 2.34.1