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: [email protected] Closes: https://syzkaller.appspot.com/bug?extid=147ba789658184f0ce04 Tested-by: [email protected] Signed-off-by: Chintan Patel <[email protected]> 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 Syrjälä) - Remove unnecessary curr = drm_vblank_count() (suggested by Thomas Zimmermann) - Fix commit message wording (“invalid userspace calls” → “delayed vblank handling”) --- 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, unsigned int pipe) last != drm_vblank_count(dev, pipe), msecs_to_jiffies(100)); - drm_WARN(dev, ret == 0, "vblank wait timed out on crtc %i\n", pipe); + if (!ret) + drm_err(dev, "vblank wait timed out on crtc %i\n", pipe); drm_vblank_put(dev, pipe); } -- 2.43.0
