[ltt-dev] [UST PATCH 2/3] ust-consumerd: fix exit race log corruption

[Jason Wessel]

In the following scenario on an SMP system the ust-consumerd can end
up not properly closing out file handles which leads to log
corruption:
  * usttrace -m -l small_quick_app_lots_of_malloc_and_free
  * The app completes and usttrace sees and sends the SIGTERM to ust-consumerd
  * The ust-consumerd main thread will exit and the _exit() handlers
    kills off the remaining pthreads without everything getting closed out

The solution to the problem is to introduce an active_thread count for
the private ustconsumer_instance.  This counter will be zeroed out
when it is safe to completely shutdown the main thread, which will
subsequently run the _exit() handlers.

Signed-off-by: Jason Wessel <jason.wessel at windriver.com>
---
 include/ust/ustconsumer.h       |    1 +
 libustconsumer/libustconsumer.c |   10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/include/ust/ustconsumer.h b/include/ust/ustconsumer.h
index f99f8f1..cde8440 100644
--- a/include/ust/ustconsumer.h
+++ b/include/ust/ustconsumer.h
@@ -89,6 +89,7 @@ struct ustconsumer_instance {
 	char *sock_path;
 	pthread_mutex_t mutex;
 	int active_buffers;
+	int active_threads;
 };
 
 /**
diff --git a/libustconsumer/libustconsumer.c b/libustconsumer/libustconsumer.c
index 6f6d4bb..a723540 100644
--- a/libustconsumer/libustconsumer.c
+++ b/libustconsumer/libustconsumer.c
@@ -543,6 +543,10 @@ void *consumer_thread(void *arg)
 	int result;
 	sigset_t sigset;
 
+	pthread_mutex_lock(&args->instance->mutex);
+	args->instance->active_threads++;
+	pthread_mutex_unlock(&args->instance->mutex);
+
 	if(args->instance->callbacks->on_new_thread)
 		args->instance->callbacks->on_new_thread(args->instance->callbacks);
 
@@ -584,6 +588,10 @@ void *consumer_thread(void *arg)
 	if(args->instance->callbacks->on_close_thread)
 		args->instance->callbacks->on_close_thread(args->instance->callbacks);
 
+	pthread_mutex_lock(&args->instance->mutex);
+	args->instance->active_threads--;
+	pthread_mutex_unlock(&args->instance->mutex);
+
 	free((void *)args->channel);
 	free(args);
 	return NULL;
@@ -735,7 +743,7 @@ int ustconsumer_start_instance(struct ustconsumer_instance *instance)
 
 		if (instance->quit_program) {
 			pthread_mutex_lock(&instance->mutex);
-			if(instance->active_buffers == 0) {
+			if(instance->active_buffers == 0 && instance->active_threads == 0) {
 				pthread_mutex_unlock(&instance->mutex);
 				break;
 			}
-- 
1.7.1