On Thu, 14 May 2026 11:34:52 -0700 Chia-I Wu olvaffe@gmail.com wrote:
On Wed, May 13, 2026 at 10:24 AM Boris Brezillon boris.brezillon@collabora.com wrote:
Define a conditional drm_dev_access guard to automate the drm_dev_{enter,exit}() sequence.
Signed-off-by: Boris Brezillon boris.brezillon@collabora.com
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