[lttng-dev] [PATCH lttng-tools] Fix: add missing UST perf counter support check

[Mathieu Desnoyers]

Report whether performance counters are supported by UST on the
architecture as soon as the user try to enable a perf counter context.

Fixes #851

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
---
 src/bin/lttng-sessiond/trace-ust.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/bin/lttng-sessiond/trace-ust.c b/src/bin/lttng-sessiond/trace-ust.c
index a3e25aa..4f06f1b 100644
--- a/src/bin/lttng-sessiond/trace-ust.c
+++ b/src/bin/lttng-sessiond/trace-ust.c
@@ -470,7 +470,12 @@ int trace_ust_context_type_event_to_ust(enum lttng_event_context_type type)
 		utype = LTTNG_UST_CONTEXT_IP;
 		break;
 	case LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER:
-		utype = LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER;
+		if (!ustctl_has_perf_counters()) {
+			utype = -1;
+			WARN("Perf counters not implemented in UST");
+		} else {
+			utype = LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER;
+		}
 		break;
 	default:
 		ERR("Invalid UST context");
-- 
2.1.1