test: create a lock file to avoid parallel udev reloads during device add

litest_add_device and litest_delete_device trigger a udev rule reload. This
messes with some test devices and when we run multiple tests in parallel we
get weird errors like "keyboard $BLAH failed the touchpad sanity test".

Still not 100% reliable to run tests in parallel, but it's vastly improved
now.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>

2 files changed, 66 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 8c14efe6..3e973d42 100644
--- a/configure.ac
+++ b/configure.ac
@@ -194,6 +194,9 @@ if test "x$build_tests" = "xyes"; then
 		AC_DEFINE_UNQUOTED(HAVE_ADDR2LINE, 1, [addr2line found])
 		AC_DEFINE_UNQUOTED(ADDR2LINE, ["$ADDR2LINE"], [Path to addr2line])
 	fi
+
+	AC_DEFINE(LITEST_UDEV_LOCKFILE, ["/tmp/litest-udev.lock"],
+		  [Lock file used to restrict udev reloads during tests])
 fi
 AM_CONDITIONAL(HAVE_LIBUNWIND, [test "x$HAVE_LIBUNWIND" = xyes])
 
diff --git a/test/litest.c b/test/litest.c
index 9b4feed6..1250b3f3 100644
--- a/test/litest.c
+++ b/test/litest.c
@@ -1164,6 +1164,58 @@ litest_restore_log_handler(struct libinput *libinput)
 	libinput_log_set_handler(libinput, litest_log_handler);
 }
 
+static inline int
+create_udev_lock_file(void)
+{
+	int lfd;
+
+	/* Running the multiple tests in parallel usually trips over udev
+	 * not being  up-to-date. We change the udev rules for every device
+	 * created, sometimes this means we end up getting the wrong udev
+	 * device, or having wrong properties applied.
+	 *
+	 * litests use the path interface and there is a window between
+	 * creating the device (which triggers udev reloads) and adding the
+	 * device to the libinput context where another udev reload may
+	 * upset things.
+	 *
+	 * To avoid this, create a lockfile on device add and device delete
+	 * to make sure that we have exclusive access to udev while
+	 * the udev rules are reloaded.
+	 */
+	do {
+		lfd = open(LITEST_UDEV_LOCKFILE, O_CREAT|O_EXCL, O_RDWR);
+
+		if (lfd == -1) {
+			struct stat st;
+			time_t now = time(NULL);
+
+			litest_assert_int_eq(errno, EEXIST);
+			msleep(10);
+
+			/* If the lock file is older than 10s, it's a
+			   leftover from some aborted test */
+			if (stat(LITEST_UDEV_LOCKFILE, &st) != -1) {
+				if (st.st_mtime < now - 10) {
+					fprintf(stderr,
+						"Removing stale lock file %s.\n",
+						LITEST_UDEV_LOCKFILE);
+					unlink(LITEST_UDEV_LOCKFILE);
+				}
+			}
+		}
+	} while (lfd < 0);
+
+	return lfd;
+}
+
+static inline void
+delete_udev_lock_file(int lfd)
+{
+	close(lfd);
+	unlink(LITEST_UDEV_LOCKFILE);
+}
+
 struct litest_device *
 litest_add_device_with_overrides(struct libinput *libinput,
 				 enum litest_device_type which,
@@ -1177,6 +1229,8 @@ litest_add_device_with_overrides(struct libinput *libinput,
 	int rc;
 	const char *path;
 
+	int lfd = create_udev_lock_file();
+
 	d = litest_create(which,
 			  name_override,
 			  id_override,
@@ -1202,6 +1256,9 @@ litest_add_device_with_overrides(struct libinput *libinput,
 		d->interface->min[ABS_Y] = libevdev_get_abs_minimum(d->evdev, ABS_Y);
 		d->interface->max[ABS_Y] = libevdev_get_abs_maximum(d->evdev, ABS_Y);
 	}
+
+	delete_udev_lock_file(lfd);
+
 	return d;
 }
 
@@ -1258,9 +1315,13 @@ litest_handle_events(struct litest_device *d)
 void
 litest_delete_device(struct litest_device *d)
 {
+	int lfd;
+
 	if (!d)
 		return;
 
+	lfd = create_udev_lock_file();
+
 	if (d->udev_rule_file) {
 		unlink(d->udev_rule_file);
 		free(d->udev_rule_file);
@@ -1278,6 +1339,8 @@ litest_delete_device(struct litest_device *d)
 	free(d->private);
 	memset(d,0, sizeof(*d));
 	free(d);
+
+	delete_udev_lock_file(lfd);
 }
 
 void