Am 16.06.2017 um 07:03 schrieb Alex Xie:
> Use rw_semaphore instead of mutex for bo_lists.
>
> In original function amdgpu_bo_list_get, the waiting
> for result->lock can be quite long while mutex
> bo_list_lock was holding. It can make other tasks
> waiting for bo_list_lock for long period too.
> Change bo_list_lock to rw_semaphore can avoid most of
> such long waiting.
>
> Secondly, this patch allows several tasks(readers of idr)
> to proceed at the same time.
>
> v2: use rcu and kref (Dave Airlie and Christian König)
>
> Signed-off-by: Alex Xie <AlexBin.Xie at amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 2 ++
> drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 40 ++++++++++++++++++++---------
> 2 files changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 063fc73..e9b3981 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -871,6 +871,8 @@ struct amdgpu_fpriv {
>
> struct amdgpu_bo_list {
> struct mutex lock;
> + struct rcu_head rhead;
> + struct kref refcount;
> struct amdgpu_bo *gds_obj;
> struct amdgpu_bo *gws_obj;
> struct amdgpu_bo *oa_obj;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> index 5af956f..efa6903 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> @@ -41,6 +41,20 @@ static int amdgpu_bo_list_set(struct amdgpu_device *adev,
> struct drm_amdgpu_bo_list_entry *info,
> unsigned num_entries);
>
> +static void amdgpu_bo_list_release_rcu(struct kref *ref)
> +{
> + unsigned i;
> + struct amdgpu_bo_list *list = container_of(ref, struct amdgpu_bo_list,
> + refcount);
> +
> + for (i = 0; i < list->num_entries; ++i)
> + amdgpu_bo_unref(&list->array[i].robj);
> +
> + mutex_destroy(&list->lock);
> + drm_free_large(list->array);
> + kfree_rcu(list, rhead);
> +}
> +
I'm probably missing something here: Why a new function and not change
the existing amdgpu_bo_list_free() to use kfree_rcu instead?
Apart from that the patch looks good to me,
Christian.
> static int amdgpu_bo_list_create(struct amdgpu_device *adev,
> struct drm_file *filp,
> struct drm_amdgpu_bo_list_entry *info,
> @@ -57,7 +71,7 @@ static int amdgpu_bo_list_create(struct amdgpu_device *adev,
>
> /* initialize bo list*/
> mutex_init(&list->lock);
> -
> + kref_init(&list->refcount);
> r = amdgpu_bo_list_set(adev, filp, list, info, num_entries);
> if (r) {
> kfree(list);
> @@ -83,14 +97,9 @@ static void amdgpu_bo_list_destroy(struct amdgpu_fpriv *fpriv, int id)
>
> mutex_lock(&fpriv->bo_list_lock);
> list = idr_remove(&fpriv->bo_list_handles, id);
> - if (list) {
> - /* Another user may have a reference to this list still */
> - mutex_lock(&list->lock);
> - mutex_unlock(&list->lock);
> - amdgpu_bo_list_free(list);
> - }
> -
> mutex_unlock(&fpriv->bo_list_lock);
> + if (list)
> + kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
> }
>
> static int amdgpu_bo_list_set(struct amdgpu_device *adev,
> @@ -185,11 +194,17 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id)
> {
> struct amdgpu_bo_list *result;
>
> - mutex_lock(&fpriv->bo_list_lock);
> + rcu_read_lock();
> result = idr_find(&fpriv->bo_list_handles, id);
> - if (result)
> - mutex_lock(&result->lock);
> - mutex_unlock(&fpriv->bo_list_lock);
> +
> + if (result) {
> + if (kref_get_unless_zero(&result->refcount))
> + mutex_lock(&result->lock);
> + else
> + result = NULL;
> + }
> + rcu_read_unlock();
> +
> return result;
> }
>
> @@ -227,6 +242,7 @@ void amdgpu_bo_list_get_list(struct amdgpu_bo_list *list,
> void amdgpu_bo_list_put(struct amdgpu_bo_list *list)
> {
> mutex_unlock(&list->lock);
> + kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
> }
>
> void amdgpu_bo_list_free(struct amdgpu_bo_list *list)
