X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=lttng-context-perf-counters.c;h=2f7132fbf26bf8db8aa9897fbfcee73cbc97e143;hb=a33c99273818348fe61ba5bbd08fa61382eab22b;hp=2e194991daf79f24d4bb9f255e99f7f1919cf2d5;hpb=8289661dc0d57d1fe33253b651100ccabe5945da;p=lttng-modules.git

diff --git a/lttng-context-perf-counters.c b/lttng-context-perf-counters.c
index 2e194991..2f7132fb 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 || IS_ERR(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;
@@ -154,6 +170,10 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
 		ret = -ENOMEM;
 		goto append_context_error;
 	}
+	if (lttng_find_context(*ctx, name_alloc))  {
+		ret = -EEXIST;
+		goto find_error;
+	}
 
 #ifdef CONFIG_HOTPLUG_CPU
 	field->u.perf_counter.nb.notifier_call =
@@ -166,7 +186,7 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
 	for_each_online_cpu(cpu) {
 		events[cpu] = perf_event_create_kernel_counter(attr,
 					cpu, NULL, overflow_callback);
-		if (!events[cpu]) {
+		if (!events[cpu] || IS_ERR(events[cpu])) {
 			ret = -EINVAL;
 			goto counter_error;
 		}
@@ -194,13 +214,14 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
 
 counter_error:
 	for_each_online_cpu(cpu) {
-		if (events[cpu])
+		if (events[cpu] && !IS_ERR(events[cpu]))
 			perf_event_release_kernel(events[cpu]);
 	}
 	put_online_cpus();
 #ifdef CONFIG_HOTPLUG_CPU
 	unregister_cpu_notifier(&field->u.perf_counter.nb);
 #endif
+find_error:
 	lttng_remove_context_field(ctx, field);
 append_context_error:
 	kfree(name_alloc);