From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755984Ab1BKKFQ (ORCPT ); Fri, 11 Feb 2011 05:05:16 -0500 Received: from ch-smtp01.sth.basefarm.net ([80.76.149.212]:50173 "EHLO ch-smtp01.sth.basefarm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752251Ab1BKKFO (ORCPT ); Fri, 11 Feb 2011 05:05:14 -0500 From: "Henrik Rydberg" Date: Fri, 11 Feb 2011 11:04:39 +0100 To: tlambert@chromium.org Cc: dmitry.torokhov@gmail.com, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Input: fixed EVIOCGRAB iterative grab/release. Message-ID: <20110211100439.GA1938@polaris.bitmath.org> References: <1297381370-16388-1-git-send-email-tlambert@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1297381370-16388-1-git-send-email-tlambert@chromium.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Originating-IP: 83.248.192.164 X-Scan-Result: No virus found in message 1Pnpr4-0003QR-5M. X-Scan-Signature: ch-smtp01.sth.basefarm.net 1Pnpr4-0003QR-5M 26c301503a29333890a0cd3cb236633b Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Terry, > Fixed order of calls in evdev_ungrab to allow iterative use of > code which grabs and releases input event devices. > > Signed-off-by: Terry Lambert > --- > drivers/input/evdev.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c > index c8471a2..0bac8da 100644 > --- a/drivers/input/evdev.c > +++ b/drivers/input/evdev.c > @@ -160,9 +160,9 @@ static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client) > if (evdev->grab != client) > return -EINVAL; > > + input_release_device(&evdev->handle); > rcu_assign_pointer(evdev->grab, NULL); > synchronize_rcu(); > - input_release_device(&evdev->handle); I imagine the current code could lead to a race situation if there were no other locks involved. However, evdev_ungrab() is always called under evdev->mutex. As Dmitry hinted, grabbing "usually works", so perhaps you could device a tiny program which reproduces the problem? Thanks, Henrik