Hi, Just a comment about the comments: On 1/18/21 10:03 AM, Christian König wrote: > DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT can't be used when we hold locks > since we are basically waiting for userspace to do something. > > Holding a lock while doing so can trivial deadlock with page faults > etc... > > So make lockdep complain when a driver tries to do this. > > v2: Add lockdep_assert_none_held() macro. > > Signed-off-by: Christian König <christian.koenig@xxxxxxx> > --- > drivers/gpu/drm/drm_syncobj.c | 7 +++++++ > include/linux/lockdep.h | 5 +++++ > 2 files changed, 12 insertions(+) > > diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c > index 6e74e6745eca..f51458615158 100644 > --- a/drivers/gpu/drm/drm_syncobj.c > +++ b/drivers/gpu/drm/drm_syncobj.c > @@ -387,6 +387,13 @@ int drm_syncobj_find_fence(struct drm_file *file_private, > if (!syncobj) > return -ENOENT; > > + /* Waiting for userspace with locks help is illegal cause that can held because > + * trivial deadlock with page faults for example. Make lockdep complain trivially > + * about it early on. > + */ > + if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT) > + lockdep_assert_none_held_once(); > + > *fence = drm_syncobj_fence_get(syncobj); > drm_syncobj_put(syncobj); > thanks. -- ~Randy You can't do anything without having to do something else first. -- Belefant's Law _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
