On Thu, 02 Oct 2025, Chintan Patel <chintanl...@gmail.com> wrote: > 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.
No need to resend for this, can be fixed while applying, but the last sentence is no longer meaningful with drm_err(). BR, Jani. > > Reported-by: syzbot+147ba789658184f0c...@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=147ba789658184f0ce04 > Tested-by: syzbot+147ba789658184f0c...@syzkaller.appspotmail.com > Signed-off-by: Chintan Patel <chintanl...@gmail.com> > > 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); > } -- Jani Nikula, Intel
