Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934692AbcJQXrj (ORCPT ); Mon, 17 Oct 2016 19:47:39 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:35753 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934292AbcJQXr2 (ORCPT ); Mon, 17 Oct 2016 19:47:28 -0400 Subject: Re: [PATCH 18/28] drm: avoid uninitialized timestamp use in wait_vblank To: Arnd Bergmann , David Airlie References: <20161017220342.1627073-1-arnd@arndb.de> <20161017221355.1861551-6-arnd@arndb.de> Cc: Linus Torvalds , linux-kernel@vger.kernel.org, Rob Clark , Daniel Vetter , Dave Airlie , =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , Alex Deucher , Gustavo Padovan , Matthew Auld , dri-devel@lists.freedesktop.org From: Mario Kleiner Message-ID: <374ecb85-dfff-ecc4-99ee-dba5ccbc169f@gmail.com> Date: Tue, 18 Oct 2016 01:47:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <20161017221355.1861551-6-arnd@arndb.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1771 Lines: 48 On 10/18/2016 12:13 AM, Arnd Bergmann wrote: > gcc warns about the timestamp in drm_wait_vblank being possibly > used without an initialization: > > drivers/gpu/drm/drm_irq.c: In function 'drm_crtc_send_vblank_event': > drivers/gpu/drm/drm_irq.c:992:24: error: 'now.tv_usec' may be used uninitialized in this function [-Werror=maybe-uninitialized] > drivers/gpu/drm/drm_irq.c:1069:17: note: 'now.tv_usec' was declared here > drivers/gpu/drm/drm_irq.c:991:23: error: 'now.tv_sec' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > This can happen if drm_vblank_count_and_time() returns 0 in its > error path. To sanitize the error case, I'm changing that function > to return a zero timestamp when it fails. > > Fixes: e6ae8687a87b ("drm: idiot-proof vblank") > Reviewed-by: David Herrmann > Cc: Rob Clark > Cc: Daniel Vetter > Signed-off-by: Arnd Bergmann > --- > First submitted in January 2016, second submission in February, > the patch is still required. > > drivers/gpu/drm/drm_irq.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c > index b969a64..48a6167 100644 > --- a/drivers/gpu/drm/drm_irq.c > +++ b/drivers/gpu/drm/drm_irq.c > @@ -952,8 +952,10 @@ static u32 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe, > u32 vblank_count; > unsigned int seq; > > - if (WARN_ON(pipe >= dev->num_crtcs)) > + if (WARN_ON(pipe >= dev->num_crtcs)) { > + *vblanktime = (struct timeval) { 0 }; > return 0; > + } > > do { > seq = read_seqbegin(&vblank->seqlock); > Looks good to me. Reviewed-by: Mario Kleiner -mario