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drm: refcnt drm_framebuffer (v4.1)

This simplifies drm fb lifetime, and if the crtc/plane needs to hold a ref to the fb when disabling a pipe until the next vblank, this avoids the need to make disabling an overlay synchronous. This is a problem that shows up when userspace is using a drm plane to implement a hw cursor.. making overlay disable synchronous causes a performance problem when x11 is rapidly enabling/disabling the hw cursor. But not making it synchronous opens up a race condition for crashing if userspace turns around and immediately deletes the fb. Refcnt'ing the fb makes it possible to solve this problem. v1: original v2: add drm_framebuffer_remove() which is called in all paths where fb->funcs->destroy() was directly called before. This cleans up the CRTCs/planes that the fb was attached to. You should only directly use drm_framebuffer_unreference() if you are also using drm_framebuffer_reference() to keep a ref to the fb. v3: add comment explaining the fb refcount v4: remove duplicate 'list_del(&fb->filp_head)' [airlied: v4.1: fix local rejection]

Rob Clark committed 14 years ago

Commit f7eff601 parent 33cce6e4 files · +85 −16Browse files

Showing the changes to include/drm (1 of 4 files). Show all

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include/drm/drm_crtc.h+14−0
@@ -218,6 +218,7 @@ struct drm_display_info { · 217 unmodified lines
218};218};
219 219
220struct drm_framebuffer_funcs {220struct drm_framebuffer_funcs {
221 /* note: use drm_framebuffer_remove() */
221 void (*destroy)(struct drm_framebuffer *framebuffer);222 void (*destroy)(struct drm_framebuffer *framebuffer);
222 int (*create_handle)(struct drm_framebuffer *fb,223 int (*create_handle)(struct drm_framebuffer *fb,
223 struct drm_file *file_priv,224 struct drm_file *file_priv,
@@ -242,6 +243,16 @@ struct drm_framebuffer_funcs { · 18 unmodified lines
242 243
243struct drm_framebuffer {244struct drm_framebuffer {
244 struct drm_device *dev;245 struct drm_device *dev;
246 /*
247 * Note that the fb is refcounted for the benefit of driver internals,
248 * for example some hw, disabling a CRTC/plane is asynchronous, and
249 * scanout does not actually complete until the next vblank. So some
250 * cleanup (like releasing the reference(s) on the backing GEM bo(s))
251 * should be deferred. In cases like this, the driver would like to
252 * hold a ref to the fb even though it has already been removed from
253 * userspace perspective.
254 */
255 struct kref refcount;
245 struct list_head head;256 struct list_head head;
246 struct drm_mode_object base;257 struct drm_mode_object base;
247 const struct drm_framebuffer_funcs *funcs;258 const struct drm_framebuffer_funcs *funcs;
@@ -919,6 +930,9 @@ extern void drm_framebuffer_set_object(struct drm_device *dev, · 671 unmodified lines
919extern int drm_framebuffer_init(struct drm_device *dev,930extern int drm_framebuffer_init(struct drm_device *dev,
920 struct drm_framebuffer *fb,931 struct drm_framebuffer *fb,
921 const struct drm_framebuffer_funcs *funcs);932 const struct drm_framebuffer_funcs *funcs);
933extern void drm_framebuffer_unreference(struct drm_framebuffer *fb);
934extern void drm_framebuffer_reference(struct drm_framebuffer *fb);
935extern void drm_framebuffer_remove(struct drm_framebuffer *fb);
922extern void drm_framebuffer_cleanup(struct drm_framebuffer *fb);936extern void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
923extern int drmfb_probe(struct drm_device *dev, struct drm_crtc *crtc);937extern int drmfb_probe(struct drm_device *dev, struct drm_crtc *crtc);
924extern int drmfb_remove(struct drm_device *dev, struct drm_framebuffer *fb);938extern int drmfb_remove(struct drm_device *dev, struct drm_framebuffer *fb);