diff --git a/piet-gpu-hal/src/dx12.rs b/piet-gpu-hal/src/dx12.rs
index 67b751d..857fe3c 100644
--- a/piet-gpu-hal/src/dx12.rs
+++ b/piet-gpu-hal/src/dx12.rs
@@ -456,6 +456,9 @@ impl crate::backend::CmdBuf<Dx12Device> for CmdBuf {
 
     unsafe fn finish(&mut self) {
         let _ = self.c.close();
+        // This is a bit of a mess. Returning the allocator to the free pool
+        // makes sense if the command list will be dropped, but not if it will
+        // be reused. Probably need to implement some logic on drop.
         if let Some(free_allocators) = self.free_allocators.upgrade() {
             free_allocators
                 .lock()
@@ -516,6 +519,9 @@ impl crate::backend::CmdBuf<Dx12Device> for CmdBuf {
             );
             self.c.resource_barrier(&[bar]);
         }
+        // Always do a memory barrier in case of UAV image access. We probably
+        // want to make these barriers more precise.
+        self.memory_barrier();
     }
 
     unsafe fn clear_buffer(&self, buffer: &Buffer, size: Option<u64>) {
@@ -558,6 +564,10 @@ impl crate::backend::CmdBuf<Dx12Device> for CmdBuf {
 
 impl crate::backend::PipelineBuilder<Dx12Device> for PipelineBuilder {
     fn add_buffers(&mut self, n_buffers: u32) {
+        // Note: if the buffer is readonly, then it needs to be bound
+        // as an SRV, not a UAV. I think that requires distinguishing
+        // readonly and read-write cases in pipeline and descriptor set
+        // creation. For now we punt.
         if n_buffers != 0 {
             self.ranges.push(d3d12::D3D12_DESCRIPTOR_RANGE {
                 RangeType: d3d12::D3D12_DESCRIPTOR_RANGE_TYPE_UAV,
@@ -572,7 +582,7 @@ impl crate::backend::PipelineBuilder<Dx12Device> for PipelineBuilder {
 
     fn add_images(&mut self, n_images: u32) {
         // These are UAV images, so the descriptor type is the same as buffers.
-        self.add_buffers(n_images)
+        self.add_buffers(n_images);
     }
 
     fn add_textures(&mut self, max_textures: u32) {
diff --git a/piet-gpu-hal/src/dx12/wrappers.rs b/piet-gpu-hal/src/dx12/wrappers.rs
index e132441..800959f 100644
--- a/piet-gpu-hal/src/dx12/wrappers.rs
+++ b/piet-gpu-hal/src/dx12/wrappers.rs
@@ -1307,7 +1307,7 @@ impl GraphicsCommandList {
 
     /// Copy an entire resource (buffer or image)
     pub unsafe fn copy_resource(&self, src: &Resource, dst: &Resource) {
-        self.0.CopyResource(src.get_mut(), dst.get_mut());
+        self.0.CopyResource(dst.get_mut(), src.get_mut());
     }
 
     pub unsafe fn copy_buffer(
diff --git a/piet-gpu-hal/src/hub.rs b/piet-gpu-hal/src/hub.rs
index b280881..2791bc9 100644
--- a/piet-gpu-hal/src/hub.rs
+++ b/piet-gpu-hal/src/hub.rs
@@ -169,6 +169,11 @@ impl Session {
                     let mut item = pending.swap_remove(i);
                     // TODO: wait is superfluous, can just reset
                     let _ = self.0.device.wait_and_reset(vec![&mut item.fence]);
+
+                    // Reuse of command buffers works on Vulkan, but not at all on
+                    // Metal and is problematic on DX12 (the allocator is returned)
+                    // to the pool. Punt for now.
+                    /*
                     let mut pool = self.0.cmd_buf_pool.lock().unwrap();
                     pool.push((item.cmd_buf, item.fence));
                     std::mem::drop(item.resources);
@@ -176,6 +181,7 @@ impl Session {
                         pool.push((staging_cmd_buf.cmd_buf, staging_cmd_buf.fence));
                         std::mem::drop(staging_cmd_buf.resources);
                     }
+                    */
                 } else {
                     i += 1;
                 }
@@ -562,11 +568,14 @@ impl SubmittedCmdBuf {
             unsafe {
                 session.device.wait_and_reset(vec![&mut item.fence])?;
             }
+            // See discussion in `poll_cleanup`
+            /*
             session
                 .cmd_buf_pool
                 .lock()
                 .unwrap()
                 .push((item.cmd_buf, item.fence));
+            */
             std::mem::drop(item.resources);
         }
         // else session dropped error?