[PATCH v3 RESEND] HID: multitouch: Add memory barriers

From: Andri Yngvason <andri@yngvason.is>
To: Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: linux-input@vger.kernel.org, Greg KH <gregkh@linuxfoundation.org>,
	Andri Yngvason <andri@yngvason.is>,
	stable@vger.kernel.org
Subject: [PATCH v3 RESEND] HID: multitouch: Add memory barriers
Date: Wed,  7 Sep 2022 15:01:59 +0000	[thread overview]
Message-ID: <20220907150159.2285460-1-andri@yngvason.is> (raw)

This fixes broken atomic checks which cause a race between the
release-timer and processing of hid input.

I noticed that contacts were sometimes sticking, even with the "sticky
fingers" quirk enabled. This fixes that problem.

Cc: stable@vger.kernel.org
Fixes: 9609827458c3 ("HID: multitouch: optimize the sticky fingers timer")
Signed-off-by: Andri Yngvason <andri@yngvason.is>
---
 V1 -> V2: Clarified where the race is and added Fixes tag as suggested
           by Greg KH
 V2 -> V3: Fix formatting of "Fixes" tag

 drivers/hid/hid-multitouch.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 2e72922e36f5..91a4d3fc30e0 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1186,7 +1186,7 @@ static void mt_touch_report(struct hid_device *hid,
 	int contact_count = -1;
 
 	/* sticky fingers release in progress, abort */
-	if (test_and_set_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
+	if (test_and_set_bit_lock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
 		return;
 
 	scantime = *app->scantime;
@@ -1267,7 +1267,7 @@ static void mt_touch_report(struct hid_device *hid,
 			del_timer(&td->release_timer);
 	}
 
-	clear_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
+	clear_bit_unlock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
 }
 
 static int mt_touch_input_configured(struct hid_device *hdev,
@@ -1699,11 +1699,11 @@ static void mt_expired_timeout(struct timer_list *t)
 	 * An input report came in just before we release the sticky fingers,
 	 * it will take care of the sticky fingers.
 	 */
-	if (test_and_set_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
+	if (test_and_set_bit_lock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags))
 		return;
 	if (test_bit(MT_IO_FLAGS_PENDING_SLOTS, &td->mt_io_flags))
 		mt_release_contacts(hdev);
-	clear_bit(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
+	clear_bit_unlock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
 }
 
 static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
-- 
2.37.2

