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([2601:1c0:5780:9200:8c84:3987:751e:970b]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7e29f2ed000sm486536b3a.1.2025.12.03.19.44.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Dec 2025 19:44:50 -0800 (PST) Message-ID: <67663eda-dce6-48e7-ad54-572bbce8b944@gmail.com> Date: Wed, 3 Dec 2025 19:44:49 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] drm/vblank: Increase timeout in drm_wait_one_vblank() To: Thomas Zimmermann , maarten.lankhorst@linux.intel.com, maxime.ripard@kernel.org, airlied@gmail.com, simona@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, syzbot+147ba789658184f0ce04@syzkaller.appspotmail.com References: <20251028034337.6341-1-chintanlike@gmail.com> <2dae83e3-6fee-4e66-964e-c7baf46eecd8@suse.de> Content-Language: en-US From: Chintan Patel In-Reply-To: <2dae83e3-6fee-4e66-964e-c7baf46eecd8@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Thomas, On 10/28/25 10:14, Thomas Zimmermann wrote: > > > Am 28.10.25 um 04:43 schrieb Chintan Patel: >> Currently, wait_event_timeout() in drm_wait_one_vblank() uses a 100ms >> timeout. Under heavy scheduling pressure or rare delayed vblank >> handling, this can trigger WARNs unnecessarily. >> >> Increase the timeout to 1000ms to reduce spurious WARNs, while still >> catching genuine issues. > > Thanks a lot. > >> >> Reported-by: syzbot+147ba789658184f0ce04@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=147ba789658184f0ce04 >> Tested-by: syzbot+147ba789658184f0ce04@syzkaller.appspotmail.com >> Signed-off-by: Chintan Patel > > Reviewed-by: Thomas Zimmermann Gentle ping on this patch. Please let me know if there are any issues with the patch, or if it requires any changes or further testing. >> >> v2: >>   - Dropped unnecessary in-code comment (suggested by Thomas Zimmermann) >>   - Removed else branch, only log timeout case >> >> v3: >>   - Replaced drm_dbg_kms()/manual logging with drm_err() (suggested by >> Ville Syrjälä) >>   - Removed unnecessary curr = drm_vblank_count() (suggested by Thomas >> Zimmermann) >>   - Fixed commit message wording ("invalid userspace calls" → "delayed >> vblank handling") >> >> v4: >>   - Keep the original drm_WARN() to catch genuine kernel issues >>   - Increased timeout from 100ms → 1000ms to reduce spurious WARNs >> (suggested by Thomas Zimmermann) >> --- >>   drivers/gpu/drm/drm_vblank.c | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c >> index 46f59883183d..f779103b261b 100644 >> --- a/drivers/gpu/drm/drm_vblank.c >> +++ b/drivers/gpu/drm/drm_vblank.c >> @@ -1303,7 +1303,7 @@ void drm_wait_one_vblank(struct drm_device *dev, >> unsigned int pipe) >>       ret = wait_event_timeout(vblank->queue, >>                    last != drm_vblank_count(dev, pipe), >> -                 msecs_to_jiffies(100)); >> +                 msecs_to_jiffies(1000)); >>       drm_WARN(dev, ret == 0, "vblank wait timed out on crtc %i\n", >> pipe); >