From 3b8c8b35de3a1a8a24169d144189b6a4db82ce10 Mon Sep 17 00:00:00 2001
From: Vladimir Kondratyev <wulf@FreeBSD.org>
Date: Wed, 22 Apr 2020 01:38:14 +0300
Subject: [PATCH] evdev: Allow open() handler to be interrupted by a signal

It is possible that the client list lock is taken by other process for too
long due to e.g. IO timeouts. Allow user to terminate open() in this case.

Reviewed by:	markj (as part of D27865)
---
 sys/dev/evdev/cdev.c          | 11 ++++++-----
 sys/dev/evdev/evdev_private.h |  9 +++++++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/sys/dev/evdev/cdev.c b/sys/dev/evdev/cdev.c
index c4550362ebce..ec60a12dbf2d 100644
--- a/sys/dev/evdev/cdev.c
+++ b/sys/dev/evdev/cdev.c
@@ -126,19 +126,20 @@ evdev_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
 	mtx_init(&client->ec_buffer_mtx, "evclient", "evdev", MTX_DEF);
 	knlist_init_mtx(&client->ec_selp.si_note, &client->ec_buffer_mtx);
 
+	ret = EVDEV_LIST_LOCK_SIG(evdev);
+	if (ret != 0)
+		goto out;
 	/* Avoid race with evdev_unregister */
-	EVDEV_LIST_LOCK(evdev);
 	if (dev->si_drv1 == NULL)
 		ret = ENODEV;
 	else
 		ret = evdev_register_client(evdev, client);
-
-	if (ret != 0)
-		evdev_revoke_client(client);
 	EVDEV_LIST_UNLOCK(evdev);
-
+out:
 	if (ret == 0)
 		ret = devfs_set_cdevpriv(client, evdev_dtor);
+	else
+		client->ec_revoked = true;
 
 	if (ret != 0) {
 		debugf(client, "cannot register evdev client");
diff --git a/sys/dev/evdev/evdev_private.h b/sys/dev/evdev/evdev_private.h
index 66a059c763bc..19636823b804 100644
--- a/sys/dev/evdev/evdev_private.h
+++ b/sys/dev/evdev/evdev_private.h
@@ -206,6 +206,15 @@ struct evdev_dev
 	else								\
 		sx_assert(&(evdev)->ev_list_lock, MA_OWNED);		\
 } while (0)
+static inline int
+EVDEV_LIST_LOCK_SIG(struct evdev_dev *evdev)
+{
+	if (evdev->ev_lock_type == EV_LOCK_MTX) {
+		EVDEV_LOCK(evdev);
+		return (0);
+	}
+	return (sx_xlock_sig(&evdev->ev_list_lock));
+}
 
 struct evdev_client
 {