Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753292Ab0KVKFi (ORCPT ); Mon, 22 Nov 2010 05:05:38 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:54545 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752750Ab0KVKFh (ORCPT ); Mon, 22 Nov 2010 05:05:37 -0500 Date: Mon, 22 Nov 2010 11:05:32 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Richard Purdie Cc: akpm , linux-kernel@vger.kernel.org, kernel@pengutronix.de, stable@kernel.org Subject: Re: [PATCH] backlight: grab ops_lock before testing bd->ops Message-ID: <20101122100532.GA4693@pengutronix.de> References: <1290418989-27653-1-git-send-email-u.kleine-koenig@pengutronix.de> <1290419947.1272.16677.camel@rex> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1290419947.1272.16677.camel@rex> User-Agent: Mutt/1.5.18 (2008-05-17) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:215:17ff:fe12:23b0 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2447 Lines: 69 Hello, On Mon, Nov 22, 2010 at 09:59:07AM +0000, Richard Purdie wrote: > On Mon, 2010-11-22 at 10:43 +0100, Uwe Kleine-K?nig wrote: > > According to the comment describing ops_lock in the definition of > > struct backlight_device and when comparing with other functions in > > backlight.c the mutex must be hold when checking ops to be non-NULL. > > > > Signed-off-by: Uwe Kleine-K?nig > > Acked-by: Richard Purdie The problem was introduced by c835ee7f4154992e6cf0674d7ee136f5d36247a4 (that is in 2.6.29-rc1). Is this relevant for stable? Best regards Uwe > > --- > > drivers/video/backlight/backlight.c | 12 ++++++------ > > 1 files changed, 6 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c > > index e207810..0870329 100644 > > --- a/drivers/video/backlight/backlight.c > > +++ b/drivers/video/backlight/backlight.c > > @@ -197,12 +197,12 @@ static int backlight_suspend(struct device *dev, pm_message_t state) > > { > > struct backlight_device *bd = to_backlight_device(dev); > > > > - if (bd->ops->options & BL_CORE_SUSPENDRESUME) { > > - mutex_lock(&bd->ops_lock); > > + mutex_lock(&bd->ops_lock); > > + if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) { > > bd->props.state |= BL_CORE_SUSPENDED; > > backlight_update_status(bd); > > - mutex_unlock(&bd->ops_lock); > > } > > + mutex_unlock(&bd->ops_lock); > > > > return 0; > > } > > @@ -211,12 +211,12 @@ static int backlight_resume(struct device *dev) > > { > > struct backlight_device *bd = to_backlight_device(dev); > > > > - if (bd->ops->options & BL_CORE_SUSPENDRESUME) { > > - mutex_lock(&bd->ops_lock); > > + mutex_lock(&bd->ops_lock); > > + if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) { > > bd->props.state &= ~BL_CORE_SUSPENDED; > > backlight_update_status(bd); > > - mutex_unlock(&bd->ops_lock); > > } > > + mutex_unlock(&bd->ops_lock); > > > > return 0; > > } > > > -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/