On Fri, Oct 2, 2020 at 2:31 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote:
>
> Hi,
>
> On Fri, Oct 02, 2020 at 09:56:20AM +0200, Daniel Vetter wrote:
> > Crank up the warning a notch and point at the right set of locking
> > functions for atomic drivers.
> >
> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > Cc: Maxime Ripard <mripard@xxxxxxxxxx>
> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > Cc: David Airlie <airlied@xxxxxxxx>
> > Cc: Daniel Vetter <daniel@xxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_atomic.c | 10 +++++-----
> > 1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index aac9122f1da2..b2d20eb6c807 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1642,11 +1642,11 @@ static void __drm_state_dump(struct drm_device *dev, struct drm_printer *p,
> > * to dmesg in case of error irq's. (Hint, you probably want to
> > * ratelimit this!)
> > *
> > - * The caller must drm_modeset_lock_all(), or if this is called
> > - * from error irq handler, it should not be enabled by default.
> > - * (Ie. if you are debugging errors you might not care that this
> > - * is racey. But calling this without all modeset locks held is
> > - * not inherently safe.)
> > + * The caller must wrap this drm_modeset_lock_all_ctx() and
> > + * drm_modeset_drop_locks(). If this is called from error irq handler, it should
> > + * not be enabled by default - if you are debugging errors you might
> > + * not care that this is racey, but calling this without all modeset locks held
> > + * is inherently unsafe.
> > */
> > void drm_state_dump(struct drm_device *dev, struct drm_printer *p)
> > {
>
> For the comment itself:
> Acked-by: Maxime Ripard <mripard@xxxxxxxxxx>
Thanks for taking a look, will merge.
> But maybe we should add some lockdep assertion to make sure we can catch
> someone actually doing this?
I think it has some use for ad-hoc debugging in random places, or
maybe as a an opt-in "tains your kernel" debug option. And then you
really don't want your useful debug output burried in a few pages of
lockdep splat first :-)
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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