From 099d1c290e2ebc3b798961a6c177c3aef5f0b789 Mon Sep 17 00:00:00 2001 From: David Herrmann Date: Wed, 29 Jan 2014 10:21:36 +0100 Subject: drm: provide device-refcount Lets not trick ourselves into thinking "drm_device" objects are not ref-counted. That's just utterly stupid. We manage "drm_minor" objects on each drm-device and each minor can have an unlimited number of open handles. Each of these handles has the drm_minor (and thus the drm_device) as private-data in the file-handle. Therefore, we may not destroy "drm_device" until all these handles are closed. It is *not* possible to reset all these pointers atomically and restrict access to them, and this is *not* how this is done! Instead, we use ref-counts to make sure the object is valid and not freed. Note that we currently use "dev->open_count" for that, which is *exactly* the same as a reference-count, just open coded. So this patch doesn't change any semantics on DRM devices (well, this patch just introduces the ref-count, anyway. Follow-up patches will replace open_count by it). Also note that generic VFS revoke support could allow us to drop this ref-count again. We could then just synchronously disable any fops->xy() calls. However, this is not the case, yet, and no such patches are in sight (and I seriously question the idea of dropping the ref-cnt again). Signed-off-by: David Herrmann --- include/drm/drmP.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/drm/drmP.h b/include/drm/drmP.h index 2c322564ca7d..4e53f1607355 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -43,6 +43,7 @@ #include #endif /* __alpha__ */ #include +#include #include #include #include @@ -1102,6 +1103,7 @@ struct drm_device { /** \name Lifetime Management */ /*@{ */ + struct kref ref; /**< Object ref-count */ struct device *dev; /**< Device structure of bus-device */ struct drm_driver *driver; /**< DRM driver managing the device */ void *dev_private; /**< DRM driver private data */ @@ -1666,7 +1668,8 @@ static __inline__ void drm_core_dropmap(struct drm_local_map *map) struct drm_device *drm_dev_alloc(struct drm_driver *driver, struct device *parent); -void drm_dev_free(struct drm_device *dev); +void drm_dev_ref(struct drm_device *dev); +void drm_dev_unref(struct drm_device *dev); int drm_dev_register(struct drm_device *dev, unsigned long flags); void drm_dev_unregister(struct drm_device *dev); /*@}*/ -- cgit v1.2.3