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drm: refcnt drm_framebuffer (v4.1)

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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]

Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Rob Clark 2012-09-05 21:48:38 +00:00 committed by Dave Airlie
parent 33cce6e980
commit f7eff60ea0
4 changed files with 85 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
drivers/gpu/drm/drm_crtc.c
View File

@ -294,6 +294,8 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb,
{
int ret;
kref_init(&fb->refcount);
ret = drm_mode_object_get(dev, &fb->base, DRM_MODE_OBJECT_FB);
if (ret)
return ret;
@ -307,6 +309,38 @@ int drm_framebuffer_init(struct drm_device *dev, struct drm_framebuffer *fb,
}
EXPORT_SYMBOL(drm_framebuffer_init);
static void drm_framebuffer_free(struct kref *kref)
{
struct drm_framebuffer *fb =
container_of(kref, struct drm_framebuffer, refcount);
fb->funcs->destroy(fb);
}
/**
* drm_framebuffer_unreference - unref a framebuffer
*
* LOCKING:
* Caller must hold mode config lock.
*/
void drm_framebuffer_unreference(struct drm_framebuffer *fb)
{
struct drm_device *dev = fb->dev;
DRM_DEBUG("FB ID: %d\n", fb->base.id);
WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
kref_put(&fb->refcount, drm_framebuffer_free);
}
EXPORT_SYMBOL(drm_framebuffer_unreference);
/**
* drm_framebuffer_reference - incr the fb refcnt
*/
void drm_framebuffer_reference(struct drm_framebuffer *fb)
{
DRM_DEBUG("FB ID: %d\n", fb->base.id);
kref_get(&fb->refcount);
}
EXPORT_SYMBOL(drm_framebuffer_reference);
/**
* drm_framebuffer_cleanup - remove a framebuffer object
* @fb: framebuffer to remove
@ -318,6 +352,32 @@ EXPORT_SYMBOL(drm_framebuffer_init);
* it, setting it to NULL.
*/
void drm_framebuffer_cleanup(struct drm_framebuffer *fb)
{
struct drm_device *dev = fb->dev;
/*
* This could be moved to drm_framebuffer_remove(), but for
* debugging is nice to keep around the list of fb's that are
* no longer associated w/ a drm_file but are not unreferenced
* yet. (i915 and omapdrm have debugfs files which will show
* this.)
*/
drm_mode_object_put(dev, &fb->base);
list_del(&fb->head);
dev->mode_config.num_fb--;
}
EXPORT_SYMBOL(drm_framebuffer_cleanup);
/**
* drm_framebuffer_remove - remove and unreference a framebuffer object
* @fb: framebuffer to remove
*
* LOCKING:
* Caller must hold mode config lock.
*
* Scans all the CRTCs and planes in @dev's mode_config. If they're
* using @fb, removes it, setting it to NULL.
*/
void drm_framebuffer_remove(struct drm_framebuffer *fb)
{
struct drm_device *dev = fb->dev;
struct drm_crtc *crtc;
@ -350,11 +410,11 @@ void drm_framebuffer_cleanup(struct drm_framebuffer *fb)
}
}
drm_mode_object_put(dev, &fb->base);
list_del(&fb->head);
dev->mode_config.num_fb--;
list_del(&fb->filp_head);
drm_framebuffer_unreference(fb);
}
EXPORT_SYMBOL(drm_framebuffer_cleanup);
EXPORT_SYMBOL(drm_framebuffer_remove);
/**
* drm_crtc_init - Initialise a new CRTC object
@ -1031,7 +1091,7 @@ void drm_mode_config_cleanup(struct drm_device *dev)
}
list_for_each_entry_safe(fb, fbt, &dev->mode_config.fb_list, head) {
fb->funcs->destroy(fb);
drm_framebuffer_remove(fb);
}
list_for_each_entry_safe(plane, plt, &dev->mode_config.plane_list,
@ -2337,11 +2397,7 @@ int drm_mode_rmfb(struct drm_device *dev,
goto out;
}
/* TODO release all crtc connected to the framebuffer */
/* TODO unhock the destructor from the buffer object */
list_del(&fb->filp_head);
fb->funcs->destroy(fb);
drm_framebuffer_remove(fb);
out:
mutex_unlock(&dev->mode_config.mutex);
@ -2491,8 +2547,7 @@ void drm_fb_release(struct drm_file *priv)
mutex_lock(&dev->mode_config.mutex);
list_for_each_entry_safe(fb, tfb, &priv->fbs, filp_head) {
list_del(&fb->filp_head);
fb->funcs->destroy(fb);
drm_framebuffer_remove(fb);
}
mutex_unlock(&dev->mode_config.mutex);
}

4
drivers/gpu/drm/exynos/exynos_drm_fbdev.c
View File

@ -266,8 +266,8 @@ static void exynos_drm_fbdev_destroy(struct drm_device *dev,
/* release drm framebuffer and real buffer */
if (fb_helper->fb && fb_helper->fb->funcs) {
fb = fb_helper->fb;
if (fb && fb->funcs->destroy)
fb->funcs->destroy(fb);
if (fb)
drm_framebuffer_remove(fb);
}
/* release linux framebuffer */

4
drivers/staging/omapdrm/omap_fbdev.c
View File

@ -276,7 +276,7 @@ fail:
if (fbi)
framebuffer_release(fbi);
if (fb)
fb->funcs->destroy(fb);
drm_framebuffer_remove(fb);
}
return ret;
@ -401,7 +401,7 @@ void omap_fbdev_free(struct drm_device *dev)
/* this will free the backing object */
if (fbdev->fb)
fbdev->fb->funcs->destroy(fbdev->fb);
drm_framebuffer_remove(fbdev->fb);
kfree(fbdev);

14
include/drm/drm_crtc.h
View File

@ -218,6 +218,7 @@ struct drm_display_info {
};
struct drm_framebuffer_funcs {
/* note: use drm_framebuffer_remove() */
void (*destroy)(struct drm_framebuffer *framebuffer);
int (*create_handle)(struct drm_framebuffer *fb,
struct drm_file *file_priv,
@ -242,6 +243,16 @@ struct drm_framebuffer_funcs {
struct drm_framebuffer {
struct drm_device *dev;
/*
* Note that the fb is refcounted for the benefit of driver internals,
* for example some hw, disabling a CRTC/plane is asynchronous, and
* scanout does not actually complete until the next vblank. So some
* cleanup (like releasing the reference(s) on the backing GEM bo(s))
* should be deferred. In cases like this, the driver would like to
* hold a ref to the fb even though it has already been removed from
* userspace perspective.
*/
struct kref refcount;
struct list_head head;
struct drm_mode_object base;
const struct drm_framebuffer_funcs *funcs;
@ -919,6 +930,9 @@ extern void drm_framebuffer_set_object(struct drm_device *dev,
extern int drm_framebuffer_init(struct drm_device *dev,
struct drm_framebuffer *fb,
const struct drm_framebuffer_funcs *funcs);
extern void drm_framebuffer_unreference(struct drm_framebuffer *fb);
extern void drm_framebuffer_reference(struct drm_framebuffer *fb);
extern void drm_framebuffer_remove(struct drm_framebuffer *fb);
extern void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
extern int drmfb_probe(struct drm_device *dev, struct drm_crtc *crtc);
extern int drmfb_remove(struct drm_device *dev, struct drm_framebuffer *fb);