Fix exit being slowed by disk util stat time

Add a cv/lock to handle exit of the disk util thread. This is a
lot cleaner than the adhoc method that was used before, and it
means that we can signal the exit immediately instead of waiting
for DISKUTIL_MSEC to pass.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/backend.c b/backend.c
index 3016e98..8303dc6 100644
--- a/backend.c
+++ b/backend.c
@@ -57,6 +57,9 @@
 
 static pthread_t disk_util_thread;
 static struct fio_mutex *disk_thread_mutex;
+static pthread_cond_t du_cond;
+static pthread_mutex_t du_lock;
+
 static struct fio_mutex *startup_mutex;
 static struct flist_head *cgroup_list;
 static char *cgroup_mnt;
@@ -1970,16 +1973,20 @@
 	update_io_ticks();
 }
 
-void wait_for_disk_thread_exit(void)
+static void wait_for_disk_thread_exit(void)
 {
-	fio_mutex_down(disk_thread_mutex);
+	void *ret;
+
+	disk_util_start_exit();
+	pthread_cond_signal(&du_cond);
+	pthread_join(disk_util_thread, &ret);
 }
 
 static void free_disk_util(void)
 {
-	disk_util_start_exit();
-	wait_for_disk_thread_exit();
 	disk_util_prune_entries();
+
+	pthread_cond_destroy(&du_cond);
 }
 
 static void *disk_thread_main(void *data)
@@ -1988,17 +1995,32 @@
 
 	fio_mutex_up(startup_mutex);
 
-	while (threads && !ret) {
-		usleep(DISK_UTIL_MSEC * 1000);
-		if (!threads)
+	while (!ret) {
+		uint64_t sec = DISK_UTIL_MSEC / 1000;
+		uint64_t nsec = (DISK_UTIL_MSEC % 1000) * 1000000;
+		struct timespec ts;
+		struct timeval tv;
+
+		gettimeofday(&tv, NULL);
+		ts.tv_sec = tv.tv_sec + sec;
+		ts.tv_nsec = (tv.tv_usec * 1000) + nsec;
+		if (ts.tv_nsec > 1000000000ULL) {
+			ts.tv_nsec -= 1000000000ULL;
+			ts.tv_sec++;
+		}
+
+		ret = pthread_cond_timedwait(&du_cond, &du_lock, &ts);
+		if (ret != ETIMEDOUT) {
+			printf("disk thread should exit %d\n", ret);
 			break;
+		}
+
 		ret = update_io_ticks();
 
 		if (!is_backend)
 			print_thread_status();
 	}
 
-	fio_mutex_up(disk_thread_mutex);
 	return NULL;
 }
 
@@ -2010,6 +2032,9 @@
 
 	disk_thread_mutex = fio_mutex_init(FIO_MUTEX_LOCKED);
 
+	pthread_cond_init(&du_cond, NULL);
+	pthread_mutex_init(&du_lock, NULL);
+
 	ret = pthread_create(&disk_util_thread, NULL, disk_thread_main, NULL);
 	if (ret) {
 		fio_mutex_remove(disk_thread_mutex);
@@ -2017,13 +2042,6 @@
 		return 1;
 	}
 
-	ret = pthread_detach(disk_util_thread);
-	if (ret) {
-		fio_mutex_remove(disk_thread_mutex);
-		log_err("Can't detatch disk util thread: %s\n", strerror(ret));
-		return 1;
-	}
-
 	dprint(FD_MUTEX, "wait on startup_mutex\n");
 	fio_mutex_down(startup_mutex);
 	dprint(FD_MUTEX, "done waiting on startup_mutex\n");
@@ -2067,6 +2085,8 @@
 
 	run_threads();
 
+	wait_for_disk_thread_exit();
+
 	if (!fio_abort) {
 		__show_run_stats();
 		if (write_bw_log) {
diff --git a/diskutil.h b/diskutil.h
index d86e4ec..f621113 100644
--- a/diskutil.h
+++ b/diskutil.h
@@ -100,8 +100,6 @@
 
 extern struct flist_head disk_list;
 
-extern void wait_for_disk_thread_exit(void);
-
 /*
  * disk util stuff
  */