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Thu, 02 Oct 2025 20:23:27 -0700 (PDT) Received: from cmpatel-home.hsd1.or.comcast.net ([2601:1c0:5780:9200:326a:8939:a05c:b9d5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-78b0206e81fsm3460145b3a.70.2025.10.02.20.23.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Oct 2025 20:23:26 -0700 (PDT) From: Chintan Patel To: maarten.lankhorst@linux.intel.com, maxime.ripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, syzbot+147ba789658184f0ce04@syzkaller.appspotmail.com, Chintan Patel Subject: [PATCH v3] drm/vblank: downgrade vblank wait timeout from WARN to error Date: Thu, 2 Oct 2025 20:23:03 -0700 Message-ID: <20251003032303.16518-1-chintanlike@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable When wait_event_timeout() in drm_wait_one_vblank() times out, the current WARN can cause unnecessary kernel panics in environments with panic_on_warn set (e.g. CI, fuzzing). These timeouts can happen under heavy scheduling pressure or in rare cases of delayed vblank handling, and are not always a kernel bug. Replace the WARN with drm_err() messages that report the timeout without crashing the system. Developers can still enable drm.debug to diagnose genuine problems. Reported-by: syzbot+147ba789658184f0ce04@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D147ba789658184f0ce04 Tested-by: syzbot+147ba789658184f0ce04@syzkaller.appspotmail.com Signed-off-by: Chintan Patel v2: - Drop unnecessary in-code comment (suggested by Thomas Zimmermann) - Remove else branch, only log timeout case v3: - Use drm_err() instead of drm_dbg_kms() (suggested by Ville Syrj=C3=A4l= =C3=A4) - Remove unnecessary curr =3D drm_vblank_count() (suggested by Thomas Zimm= ermann) - Fix commit message wording (=E2=80=9Cinvalid userspace calls=E2=80=9D = =E2=86=92 =E2=80=9Cdelayed vblank handling=E2=80=9D) Acked-by: Thomas Zimmermann --- drivers/gpu/drm/drm_vblank.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 46f59883183d..0664aea1b924 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1305,7 +1305,8 @@ void drm_wait_one_vblank(struct drm_device *dev, unsi= gned int pipe) last !=3D drm_vblank_count(dev, pipe), msecs_to_jiffies(100)); =20 - drm_WARN(dev, ret =3D=3D 0, "vblank wait timed out on crtc %i\n", pipe); + if (!ret) + drm_err(dev, "vblank wait timed out on crtc %i\n", pipe); =20 drm_vblank_put(dev, pipe); } --=20 2.43.0