Am 17.09.21 um 16:35 schrieb Daniel Vetter:
On Fri, Sep 17, 2021 at 02:34:50PM +0200, Christian König wrote:This makes the function much simpler since the complex retry logic is now handled else where. Signed-off-by: Christian König <christian.koenig@xxxxxxx> --- 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?
Exactly that's what I wanted to avoid since the is_first (or whatever) function should only be used inside of the dma_resv.c code.
On the other hand I can just make that static here and document that it should never be exported.
Christian.
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 <daniel.vetter@xxxxxxxx>+ 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
