Re: [PATCH 03/26] dma-buf: use new iterator in dma_resv_copy_fences
From: Daniel Vetter <hidden>
Date: 2021-09-17 14:35:27
Also in:
dri-devel, intel-gfx
On Fri, Sep 17, 2021 at 02:34:50PM +0200, Christian König wrote:
quoted hunk ↗ jump to hunk
This makes the function much simpler since the complex retry logic is now handled else where. Signed-off-by: Christian König <christian.koenig@amd.com> --- drivers/dma-buf/dma-resv.c | 86 ++++++++++++++++---------------------- 1 file changed, 35 insertions(+), 51 deletions(-)diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index a3c79a99fb44..406150dea5e4 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c@@ -426,74 +426,58 @@ EXPORT_SYMBOL_GPL(dma_resv_iter_walk); */ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src) { - struct dma_resv_list *src_list, *dst_list; - struct dma_fence *old, *new; - unsigned int i; + struct dma_resv_iter cursor; + struct dma_resv_list *list; + struct dma_fence *f, *excl; dma_resv_assert_held(dst); - rcu_read_lock(); - src_list = dma_resv_shared_list(src); - -retry: - if (src_list) { - unsigned int shared_count = src_list->shared_count; - - rcu_read_unlock(); + list = NULL; + excl = NULL; - dst_list = dma_resv_list_alloc(shared_count); - if (!dst_list) - return -ENOMEM; + rcu_read_lock(); + dma_resv_iter_begin(&cursor, src, true); + dma_resv_for_each_fence_unlocked(&cursor, f) { - rcu_read_lock(); - src_list = dma_resv_shared_list(src); - if (!src_list || src_list->shared_count > shared_count) { - kfree(dst_list); - goto retry; - } + if (cursor.is_first) {
Maybe have a wrapper for this, like dma_resv_iter_is_reset or is_first or is_restart (my preference) with some nice docs that this returns true everytime we had to restart the sequence? Otherwise I fully agree, this is so much better with all the hairy restarting and get_rcu and test_bit shovelled away somewhere. Either way (but I much prefer a wrapper for is_first): Reviewed-by: Daniel Vetter <redacted>
+ dma_resv_list_free(list);
+ dma_fence_put(excl);
- dst_list->shared_count = 0;
- for (i = 0; i < src_list->shared_count; ++i) {
- struct dma_fence __rcu **dst;
- struct dma_fence *fence;
+ if (cursor.fences) {
+ unsigned int cnt = cursor.fences->shared_count;
- fence = rcu_dereference(src_list->shared[i]);
- if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
- &fence->flags))
- continue;
+ rcu_read_unlock();
+ list = dma_resv_list_alloc(cnt);
+ if (!list) {
+ dma_resv_iter_end(&cursor);
+ return -ENOMEM;
+ }
- if (!dma_fence_get_rcu(fence)) {
- dma_resv_list_free(dst_list);
- src_list = dma_resv_shared_list(src);
- goto retry;
- }
+ list->shared_count = 0;
+ rcu_read_lock();
- if (dma_fence_is_signaled(fence)) {
- dma_fence_put(fence);
- continue;
+ } else {
+ list = NULL;
}
-
- dst = &dst_list->shared[dst_list->shared_count++];
- rcu_assign_pointer(*dst, fence);
+ excl = NULL;
}
- } else {
- dst_list = NULL;
- }
- new = dma_fence_get_rcu_safe(&src->fence_excl);
+ dma_fence_get(f);
+ if (dma_resv_iter_is_exclusive(&cursor))
+ excl = f;
+ else
+ RCU_INIT_POINTER(list->shared[list->shared_count++], f);
+ }
+ dma_resv_iter_end(&cursor);
rcu_read_unlock();
- src_list = dma_resv_shared_list(dst);
- old = dma_resv_excl_fence(dst);
-
write_seqcount_begin(&dst->seq);
- /* write_seqcount_begin provides the necessary memory barrier */
- RCU_INIT_POINTER(dst->fence_excl, new);
- RCU_INIT_POINTER(dst->fence, dst_list);
+ excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
+ list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
write_seqcount_end(&dst->seq);
- dma_resv_list_free(src_list);
- dma_fence_put(old);
+ dma_resv_list_free(list);
+ dma_fence_put(excl);
return 0;
}
--
2.25.1-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch