On Wed, Feb 21, 2018 at 10:20:03AM -0500, Rob Clark wrote:
On Wed, Feb 21, 2018 at 10:07 AM, Ville Syrjälä ville.syrjala@linux.intel.com wrote:
On Wed, Feb 21, 2018 at 09:54:49AM -0500, Rob Clark wrote:
On Wed, Feb 21, 2018 at 9:49 AM, Ville Syrjälä ville.syrjala@linux.intel.com wrote:
On Wed, Feb 21, 2018 at 09:37:21AM -0500, Rob Clark wrote:
Follow the same pattern of locking as with other state objects. This avoids boilerplate in the driver.
I'm not sure we really want to do this. What if the driver wants a custom locking scheme for this state?
That seems like something we want to discourage, ie. all the more reason for this patch.
There is no reason drivers could not split their global state into multiple private objs's, each with their own lock, for more fine grained locking. That is basically the only valid reason I can think of for "custom locking".
In i915 we have at least one case that would want something close to an rwlock. Any crtc lock is enough for read, need all of them for write. Though if we wanted to use private objs for that we might need to actually make the states refcounted as well, otherwise I can imagine we might land in some use-after-free issues once again.
Maybe we could duplicate the state into per-crtc and global copies, but then we have to keep all of those in sync somehow which doesn't sound particularly pleasant.
Or just keep your own driver lock for read, and use that plus the core modeset lock for write?
If we can't add the private obj to the state we can't really use it.
BR, -R
(And ofc drivers could add there own locks in addition to what is done by core, but I'd rather look at that on a case by case basis, rather than it being part of the boilerplate in each driver.)
BR, -R
Signed-off-by: Rob Clark robdclark@gmail.com
drivers/gpu/drm/drm_atomic.c | 9 ++++++++- include/drm/drm_atomic.h | 5 +++++ 2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index fc8c4da409ff..004e621ab307 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -1078,6 +1078,8 @@ drm_atomic_private_obj_init(struct drm_private_obj *obj, { memset(obj, 0, sizeof(*obj));
drm_modeset_lock_init(&obj->lock);obj->state = state; obj->funcs = funcs;} @@ -1093,6 +1095,7 @@ void drm_atomic_private_obj_fini(struct drm_private_obj *obj) { obj->funcs->atomic_destroy_state(obj, obj->state);
drm_modeset_lock_fini(&obj->lock);} EXPORT_SYMBOL(drm_atomic_private_obj_fini);
@@ -1113,7 +1116,7 @@ struct drm_private_state * drm_atomic_get_private_obj_state(struct drm_atomic_state *state, struct drm_private_obj *obj) {
int index, num_objs, i;
int index, num_objs, i, ret; size_t size; struct __drm_private_objs_state *arr; struct drm_private_state *obj_state;@@ -1122,6 +1125,10 @@ drm_atomic_get_private_obj_state(struct drm_atomic_state *state, if (obj == state->private_objs[i].ptr) return state->private_objs[i].state;
ret = drm_modeset_lock(&obj->lock, state->acquire_ctx);if (ret)return ERR_PTR(ret);num_objs = state->num_private_objs + 1; size = sizeof(*state->private_objs) * num_objs; arr = krealloc(state->private_objs, size, GFP_KERNEL);diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h index 09076a625637..9ae53b73c9d2 100644 --- a/include/drm/drm_atomic.h +++ b/include/drm/drm_atomic.h @@ -218,6 +218,11 @@ struct drm_private_state_funcs {
- &drm_modeset_lock is required to duplicate and update this object's state.
*/ struct drm_private_obj {
/*** @lock: Modeset lock to protect the state object.*/struct drm_modeset_lock lock;/** * @state: Current atomic state for this driver private object. */-- 2.14.3
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-- Ville Syrjälä Intel OTC
-- Ville Syrjälä Intel OTC