On 09/26/2018 06:35 PM, Christian König wrote:
Am 26.09.2018 um 18:18 schrieb Thomas Hellstrom:
Export ttm_bo_reference_unless_doomed() to be used when looking up
buffer
objects that are removed from the lookup structure in the destructor.
Cc: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Reviewed-by: Sinclair Yeh <syeh@xxxxxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 3 +--
include/drm/ttm/ttm_bo_api.h | 18 ++++++++++++++++++
2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c
b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 6fe91c1b692d..ec4b09366213 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -409,8 +409,7 @@ static struct ttm_buffer_object
*ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
node = drm_vma_offset_lookup_locked(&bdev->vma_manager, offset,
pages);
if (likely(node)) {
bo = container_of(node, struct ttm_buffer_object, vma_node);
- if (!kref_get_unless_zero(&bo->kref))
- bo = NULL;
+ bo = ttm_bo_reference_unless_doomed(bo);
}
drm_vma_offset_unlock_lookup(&bdev->vma_manager);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 8c19470785e2..b6bf6b086576 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -312,6 +312,24 @@ ttm_bo_reference(struct ttm_buffer_object *bo)
return bo;
}
+/**
+ * ttm_bo_reference_unless_doomed - reference a struct
ttm_buffer_object unless
+ * its refcount has already reached zero.
+ * @bo: The buffer object.
+ *
+ * Used to reference a TTM buffer object in lookups where the object
is removed
+ * from the lookup structure during the destructor and for RCU lookups.
+ *
+ * Returns: @bo if the referencing was successful, NULL otherwise.
+ */
+static inline __must_check struct ttm_buffer_object *
+ttm_bo_reference_unless_doomed(struct ttm_buffer_object *bo)
Please name that ttm_bo_get_rcu(), we are in the process of renaming
ttm_bo_reference into ttm_bo_get as well.
Could we call it ttm_bo_get_unless_doomed() or ttm_bo_get_unless_zero()
to be even more consistent. (It's not restricted to rcu as the VM usage
shows). Also "doomed" is more relevant for objects, "zero" is more
relevant for the refcount itself?
/Thomas
Christian.
+{
+ if (!kref_get_unless_zero(&bo->kref))
+ return NULL;
+ return bo;
+}
+
/**
* ttm_bo_wait - wait for buffer idle.
*
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