Perf counter support: check if busy

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lttng-context-perf-counters.c b/lttng-context-perf-counters.c
index 005c651039e045fb6cb34142b5f8eb355497b515..2f131d61e32f2cdbd4f7b152b478f7c60e3be6c2 100644 (file)
--- a/lttng-context-perf-counters.c
+++ b/lttng-context-perf-counters.c
@@ -37,8 +37,12 @@ void perf_counter_record(struct lttng_ctx_field *field,
 
        event = field->u.perf_counter->e[ctx->cpu];
        if (likely(event)) {
-               event->pmu->read(event);
-               value = local64_read(&event->count);
+               if (unlikely(event->state == PERF_EVENT_STATE_ERROR)) {
+                       value = 0;
+               } else {
+                       event->pmu->read(event);
+                       value = local64_read(&event->count);
+               }
        } else {
                /*
                 * Perf chooses not to be clever and not to support enabling a
@@ -114,6 +118,10 @@ int __cpuinit lttng_perf_counter_cpu_hp_callback(struct notifier_block *nb,
                                cpu, NULL, overflow_callback);
                if (!pevent || IS_ERR(pevent))
                        return NOTIFY_BAD;
+               if (pevent->state == PERF_EVENT_STATE_ERROR) {
+                       perf_event_release_kernel(pevent);
+                       return NOTIFY_BAD;
+               }
                barrier();      /* Create perf counter before setting event */
                events[cpu] = pevent;
                break;
@@ -200,6 +208,10 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
                        ret = -EINVAL;
                        goto counter_error;
                }
+               if (events[cpu]->state == PERF_EVENT_STATE_ERROR) {
+                       ret = -EBUSY;
+                       goto counter_busy;
+               }
        }
        put_online_cpus();
 
@@ -221,6 +233,7 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
        wrapper_vmalloc_sync_all();
        return 0;
 
+counter_busy:
 counter_error:
        for_each_online_cpu(cpu) {
                if (events[cpu] && !IS_ERR(events[cpu]))