Tests: race between consumer pause and trace start/stop

This fixes two problems with the current test.

1. Starting the tracing before pausing the consumption can result
in an arbitrary number of buffer usage conditions being sent to
the client as the buffers can be filled and emptied a number of
times.

2. Resuming the consumption before stopping tracing can, in a
similar way as '1', result in an arbitrary number of notifications
being sent to the client.

Note that the non-blocking stop is used since the blocking
variant would wait for pending data to be flushed forever since
the consumption is paused. Hence, we stop the tracing, resume
the consumption, and wait for the buffers to be flushed explicitly
using the lttng_data_pending() call. No sleeps are performed in
that loop since those could hide races triggered by this test.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/tests/regression/tools/notification/notification.c b/tests/regression/tools/notification/notification.c
index 6c52bed01d864f8f40e574cd266dd0e5648584f8..de8734603fd309ba8d42db1cffac97015b5cd3e9 100644 (file)
--- a/tests/regression/tools/notification/notification.c
+++ b/tests/regression/tools/notification/notification.c
@@ -374,6 +374,17 @@ end:
        lttng_action_destroy(action);
 }
 
+static
+void wait_data_pending(const char *session_name)
+{
+       int ret;
+
+       do {
+               ret = lttng_data_pending(session_name);
+               assert(ret >= 0);
+       } while (ret != 0);
+}
+
 void test_notification_channel(const char *session_name, const char *channel_name, const enum lttng_domain_type domain_type, const char **argv)
 {
        int ret = 0;
@@ -575,8 +586,8 @@ void test_notification_channel(const char *session_name, const char *channel_nam
        ok(nc_status == LTTNG_NOTIFICATION_CHANNEL_STATUS_ALREADY_SUBSCRIBED, "Subscribe to a condition for which subscription was already done");
 
        /* Wait for notification to happen */
-       lttng_start_tracing(session_name);
        stop_consumer(argv);
+       lttng_start_tracing(session_name);
 
        /* Wait for high notification */
        nc_status = lttng_notification_channel_get_next_notification(notification_channel, &notification);
@@ -588,8 +599,9 @@ void test_notification_channel(const char *session_name, const char *channel_nam
        notification = NULL;
 
        suspend_application();
+       lttng_stop_tracing_no_wait(session_name);
        resume_consumer(argv);
-       lttng_stop_tracing(session_name);
+       wait_data_pending(session_name);
 
        /*
         * Test that communication still work even if there is notification
@@ -611,9 +623,9 @@ void test_notification_channel(const char *session_name, const char *channel_nam
        notification = NULL;
 
        /* Stop consumer to force a high notification */
+       stop_consumer(argv);
        resume_application();
        lttng_start_tracing(session_name);
-       stop_consumer(argv);
 
        nc_status = lttng_notification_channel_get_next_notification(notification_channel, &notification);
        ok(nc_status == LTTNG_NOTIFICATION_CHANNEL_STATUS_OK && notification &&
@@ -623,9 +635,9 @@ void test_notification_channel(const char *session_name, const char *channel_nam
        notification = NULL;
 
        suspend_application();
-       /* Resume consumer to allow event consumption */
+       lttng_stop_tracing_no_wait(session_name);
        resume_consumer(argv);
-       lttng_stop_tracing(session_name);
+       wait_data_pending(session_name);
 
        nc_status = lttng_notification_channel_get_next_notification(notification_channel, &notification);
        ok(nc_status == LTTNG_NOTIFICATION_CHANNEL_STATUS_OK && notification &&
@@ -634,10 +646,10 @@ void test_notification_channel(const char *session_name, const char *channel_nam
        lttng_notification_destroy(notification);
        notification = NULL;
 
+       stop_consumer(argv);
        resume_application();
        /* Stop consumer to force a high notification */
        lttng_start_tracing(session_name);
-       stop_consumer(argv);
 
        nc_status = lttng_notification_channel_get_next_notification(notification_channel, &notification);
        ok(nc_status == LTTNG_NOTIFICATION_CHANNEL_STATUS_OK && notification &&
@@ -647,8 +659,10 @@ void test_notification_channel(const char *session_name, const char *channel_nam
        notification = NULL;
 
        /* Resume consumer to allow event consumption */
+       suspend_application();
+       lttng_stop_tracing_no_wait(session_name);
        resume_consumer(argv);
-       lttng_stop_tracing(session_name);
+       wait_data_pending(session_name);
 
        nc_status = lttng_notification_channel_unsubscribe(notification_channel, low_condition);
        ok(nc_status == LTTNG_NOTIFICATION_CHANNEL_STATUS_OK, "Unsubscribe low condition with pending notification");