selftests/user_events: Ensure auto cleanup works as expected

User events now auto cleanup upon the last reference put. Update
ftrace_test to ensure this works as expected. Ensure EBUSY delays
while event is being deleted do not cause transient failures by
waiting and re-attempting.

Link: https://lkml.kernel.org/r/20230614163336.5797-5-beaub@linux.microsoft.com

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/testing/selftests/user_events/ftrace_test.c

@@ -102,30 +102,56 @@ static int get_print_fmt(char *buffer, int len)
 	return -1;
 }
 
+static bool wait_for_delete(void)
+{
+	int i;
+
+	for (i = 0; i < 1000; ++i) {
+		int fd = open(enable_file, O_RDONLY);
+
+		if (fd == -1)
+			return true;
+
+		close(fd);
+		usleep(1000);
+	}
+
+	return false;
+}
+
 static int clear(int *check)
 {
 	struct user_unreg unreg = {0};
+	int fd;
 
 	unreg.size = sizeof(unreg);
 	unreg.disable_bit = 31;
 	unreg.disable_addr = (__u64)check;
 
-	int fd = open(data_file, O_RDWR);
+	fd = open(data_file, O_RDWR);
 
 	if (fd == -1)
 		return -1;
 
 	if (ioctl(fd, DIAG_IOCSUNREG, &unreg) == -1)
 		if (errno != ENOENT)
-			return -1;
-
-	if (ioctl(fd, DIAG_IOCSDEL, "__test_event") == -1)
-		if (errno != ENOENT)
-			return -1;
+			goto fail;
+
+	if (ioctl(fd, DIAG_IOCSDEL, "__test_event") == -1) {
+		if (errno == EBUSY) {
+			if (!wait_for_delete())
+				goto fail;
+		} else if (errno != ENOENT)
+			goto fail;
+	}
 
 	close(fd);
 
 	return 0;
+fail:
+	close(fd);
+
+	return -1;
 }
 
 static int check_print_fmt(const char *event, const char *expected, int *check)
@@ -155,16 +181,17 @@ static int check_print_fmt(const char *event, const char *expected, int *check)
 	/* Register should work */
 	ret = ioctl(fd, DIAG_IOCSREG, &reg);
 
-	close(fd);
-
 	if (ret != 0) {
+		close(fd);
 		printf("Reg failed in fmt\n");
 		return ret;
 	}
 
 	/* Ensure correct print_fmt */
 	ret = get_print_fmt(print_fmt, sizeof(print_fmt));
 
+	close(fd);
+
 	if (ret != 0)
 		return ret;
 
@@ -256,10 +283,10 @@ TEST_F(user, register_events) {
 	unreg.disable_bit = 30;
 	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSUNREG, &unreg));
 
-	/* Delete should work only after close and unregister */
+	/* Delete should have been auto-done after close and unregister */
 	close(self->data_fd);
-	self->data_fd = open(data_file, O_RDWR);
-	ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSDEL, "__test_event"));
+
+	ASSERT_EQ(true, wait_for_delete());
 }
 
 TEST_F(user, write_events) {