We take advantage of that syncobj->fence is an RCU-protected pointer, and so sparse complains that it is lacking annotation.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk --- include/drm/drm_syncobj.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h index c00fee539822..455660673259 100644 --- a/include/drm/drm_syncobj.h +++ b/include/drm/drm_syncobj.h @@ -49,7 +49,7 @@ struct drm_syncobj { * This field should not be used directly. Use drm_syncobj_fence_get * and drm_syncobj_replace_fence instead. */ - struct dma_fence *fence; + struct dma_fence __rcu *fence; /** * @cb_list: * List of callbacks to call when the fence gets replaced
In order to silent sparse in dma_fence_get_rcu_safe(), we need to mark the incoming fence object as being RCU protected and not the pointer to the object.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk --- include/linux/dma-fence.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 171895072435..bad861f8f914 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -242,7 +242,7 @@ static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence) * The caller is required to hold the RCU read lock. */ static inline struct dma_fence * -dma_fence_get_rcu_safe(struct dma_fence * __rcu *fencep) +dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep) { do { struct dma_fence *fence;
On Fri, Sep 01, 2017 at 03:57:06PM +0100, Chris Wilson wrote:
We take advantage of that syncobj->fence is an RCU-protected pointer, and so sparse complains that it is lacking annotation.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk
include/drm/drm_syncobj.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h index c00fee539822..455660673259 100644 --- a/include/drm/drm_syncobj.h +++ b/include/drm/drm_syncobj.h @@ -49,7 +49,7 @@ struct drm_syncobj { * This field should not be used directly. Use drm_syncobj_fence_get * and drm_syncobj_replace_fence instead. */
- struct dma_fence *fence;
- struct dma_fence __rcu *fence;
drm_syncobj.c uses that pointer directly quite a bit which seems to generate more sparse warnings.
Would something like this be needed (just typing stuff blindly here)?
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c index 0422b8c2c2e7..1786787ecc30 100644 --- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -106,7 +106,8 @@ static int drm_syncobj_fence_get_or_add_callback(struct drm_syncobj *syncobj, * callback when a fence has already been set. */ if (syncobj->fence) { - *fence = dma_fence_get(syncobj->fence); + *fence = dma_fence_get(rcu_dereference_protected(syncobj->fence, + lockdep_is_held(&syncobj->lock))); ret = 1; } else { *fence = NULL; @@ -168,8 +169,9 @@ void drm_syncobj_replace_fence(struct drm_syncobj *syncobj,
spin_lock(&syncobj->lock);
- old_fence = syncobj->fence; - syncobj->fence = fence; + old_fence = rcu_dereference_protected(syncobj->fence, + lockdep_is_held(&syncobj->lock)); + rcu_assign_pointer(syncobj->fence, fence);
if (fence != old_fence) { list_for_each_entry_safe(cur, tmp, &syncobj->cb_list, node) { @@ -613,7 +615,8 @@ static void syncobj_wait_syncobj_func(struct drm_syncobj *syncobj, container_of(cb, struct syncobj_wait_entry, syncobj_cb);
/* This happens inside the syncobj lock */ - wait->fence = dma_fence_get(syncobj->fence); + wait->fence = dma_fence_get(rcu_dereference_protected(syncobj->fence, + lockdep_is_held(&syncobj->lock))); wake_up_process(wait->task); }
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