On Thu, 14 May 2026 11:34:52 -0700 Chia-I Wu <[email protected]> wrote:
> On Wed, May 13, 2026 at 10:24 AM Boris Brezillon > <[email protected]> wrote: > > > > Define a conditional drm_dev_access guard to automate the > > drm_dev_{enter,exit}() sequence. > > > > Signed-off-by: Boris Brezillon <[email protected]> > > --- > > include/drm/drm_drv.h | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h > > index 42fc085f986d..79d1958f93e4 100644 > > --- a/include/drm/drm_drv.h > > +++ b/include/drm/drm_drv.h > > @@ -490,6 +490,15 @@ void drm_dev_unplug(struct drm_device *dev); > > int drm_dev_wedged_event(struct drm_device *dev, unsigned long method, > > struct drm_wedge_task_info *info); > > > > +/* > > + * Only the conditional drm_dev_access guard is valid. The drm_dev one is > > + * here so we can extend it with a conditional variant. > > + */ > > +DEFINE_LOCK_GUARD_1(drm_dev, struct drm_device, > > + { WARN_ON("Use cond guards"); _T->idx = -1; }, > > + drm_dev_exit(_T->idx), int idx); > If this is ever mis-used, drm_dev_exit(-1) seems to cause OOB access. > Is BUG more appropriate than WARN_ON? I actually had if (_T->idx >= 0) drm_dev_exit(_T->idx), at some point, and I ditched it thinking the WARN_ON_ONCE() in srcu_read_unlock() would cover for that. I can add it back, of course. I'd be fine with a BUG_ON() too, but every time I tried to add one I've been encouraged to handle the unexpected case instead. Ideally, we would have a DEFINE_LOCK_GUARD_COND() variant that, instead of expanding a non-conditional one, would define the whole thing so that the non-conditional variant is never exposed. > > > +DEFINE_LOCK_GUARD_1_COND(drm_dev, _access, drm_dev_enter(_T->lock, > > &_T->idx)); > > + > > /** > > * drm_dev_is_unplugged - is a DRM device unplugged > > * @dev: DRM device > > > > -- > > 2.54.0 > >
