move PendingWrites into the Queue

The `Device` should not contain any `Arc`s to resources as that creates cycles (since all resources hold strong references to the `Device`).
Note that `PendingWrites` internally has `Arc`s to resources.

I think this change also makes more sense conceptually since most operations that use `PendingWrites` are on the `Queue`.

wgpu-core/src/command/ray_tracing.rs

@@ -1,5 +1,5 @@
 use crate::{
-    device::queue::TempResource,
+    device::{queue::TempResource, Device},
     global::Global,
     hub::Hub,
     id::CommandEncoderId,
@@ -20,10 +20,7 @@ use crate::{
 use wgt::{math::align_to, BufferUsages, Features};
 
 use super::CommandBufferMutable;
-use crate::device::queue::PendingWrites;
 use hal::BufferUses;
-use std::mem::ManuallyDrop;
-use std::ops::DerefMut;
 use std::{
     cmp::max,
     num::NonZeroU64,
@@ -184,7 +181,7 @@ impl Global {
             build_command_index,
             &mut buf_storage,
             hub,
-            device.pending_writes.lock().deref_mut(),
+            device,
         )?;
 
         let snatch_guard = device.snatchable_lock.read();
@@ -248,7 +245,9 @@ impl Global {
                 .get()
                 .map_err(|_| BuildAccelerationStructureError::InvalidTlasId)?;
             cmd_buf_data.trackers.tlas_s.set_single(tlas.clone());
-            device.pending_writes.lock().insert_tlas(&tlas);
+            if let Some(queue) = device.get_queue() {
+                queue.pending_writes.lock().insert_tlas(&tlas);
+            }
 
             cmd_buf_data.tlas_actions.push(TlasAction {
                 tlas: tlas.clone(),
@@ -349,10 +348,12 @@ impl Global {
             }
         }
 
-        device
+        if let Some(queue) = device.get_queue() {
+            queue
                 .pending_writes
                 .lock()
                 .consume_temp(TempResource::ScratchBuffer(scratch_buffer));
+        }
 
         Ok(())
     }
@@ -495,7 +496,7 @@ impl Global {
             build_command_index,
             &mut buf_storage,
             hub,
-            device.pending_writes.lock().deref_mut(),
+            device,
         )?;
 
         let snatch_guard = device.snatchable_lock.read();
@@ -516,7 +517,9 @@ impl Global {
                 .get(package.tlas_id)
                 .get()
                 .map_err(|_| BuildAccelerationStructureError::InvalidTlasId)?;
-            device.pending_writes.lock().insert_tlas(&tlas);
+            if let Some(queue) = device.get_queue() {
+                queue.pending_writes.lock().insert_tlas(&tlas);
+            }
             cmd_buf_data.trackers.tlas_s.set_single(tlas.clone());
 
             tlas_lock_store.push((Some(package), tlas.clone()))
@@ -742,17 +745,21 @@ impl Global {
             }
 
             if let Some(staging_buffer) = staging_buffer {
-                device
+                if let Some(queue) = device.get_queue() {
+                    queue
                         .pending_writes
                         .lock()
                         .consume_temp(TempResource::StagingBuffer(staging_buffer));
                 }
             }
+        }
 
-        device
+        if let Some(queue) = device.get_queue() {
+            queue
                 .pending_writes
                 .lock()
                 .consume_temp(TempResource::ScratchBuffer(scratch_buffer));
+        }
 
         Ok(())
     }
@@ -839,7 +846,7 @@ fn iter_blas<'a>(
     build_command_index: NonZeroU64,
     buf_storage: &mut Vec<TriangleBufferStore<'a>>,
     hub: &Hub,
-    pending_writes: &mut ManuallyDrop<PendingWrites>,
+    device: &Device,
 ) -> Result<(), BuildAccelerationStructureError> {
     let mut temp_buffer = Vec::new();
     for entry in blas_iter {
@@ -849,7 +856,9 @@ fn iter_blas<'a>(
             .get()
             .map_err(|_| BuildAccelerationStructureError::InvalidBlasId)?;
         cmd_buf_data.trackers.blas_s.set_single(blas.clone());
-        pending_writes.insert_blas(&blas);
+        if let Some(queue) = device.get_queue() {
+            queue.pending_writes.lock().insert_blas(&blas);
+        }
 
         cmd_buf_data.blas_actions.push(BlasAction {
             blas: blas.clone(),

wgpu-core/src/device/queue.rs

@@ -14,7 +14,7 @@ use crate::{
     hal_label,
     id::{self, QueueId},
     init_tracker::{has_copy_partial_init_tracker_coverage, TextureInitRange},
-    lock::RwLockWriteGuard,
+    lock::{rank, Mutex, RwLockWriteGuard},
     resource::{
         Buffer, BufferAccessError, BufferMapState, DestroyedBuffer, DestroyedResourceError,
         DestroyedTexture, Fallible, FlushedStagingBuffer, InvalidResourceError, Labeled,
@@ -42,14 +42,59 @@ use super::Device;
 pub struct Queue {
     raw: ManuallyDrop<Box<dyn hal::DynQueue>>,
     pub(crate) device: Arc<Device>,
+    pub(crate) pending_writes: Mutex<ManuallyDrop<PendingWrites>>,
 }
 
 impl Queue {
-    pub(crate) fn new(device: Arc<Device>, raw: Box<dyn hal::DynQueue>) -> Self {
-        Queue {
+    pub(crate) fn new(
+        device: Arc<Device>,
+        raw: Box<dyn hal::DynQueue>,
+    ) -> Result<Self, DeviceError> {
+        let pending_encoder = device
+            .command_allocator
+            .acquire_encoder(device.raw(), raw.as_ref())
+            .map_err(DeviceError::from_hal);
+
+        let pending_encoder = match pending_encoder {
+            Ok(pending_encoder) => pending_encoder,
+            Err(e) => {
+                device.release_queue(raw);
+                return Err(e);
+            }
+        };
+
+        let mut pending_writes = PendingWrites::new(pending_encoder);
+
+        let zero_buffer = device.zero_buffer.as_ref();
+        pending_writes.activate();
+        unsafe {
+            pending_writes
+                .command_encoder
+                .transition_buffers(&[hal::BufferBarrier {
+                    buffer: zero_buffer,
+                    usage: hal::BufferUses::empty()..hal::BufferUses::COPY_DST,
+                }]);
+            pending_writes
+                .command_encoder
+                .clear_buffer(zero_buffer, 0..super::ZERO_BUFFER_SIZE);
+            pending_writes
+                .command_encoder
+                .transition_buffers(&[hal::BufferBarrier {
+                    buffer: zero_buffer,
+                    usage: hal::BufferUses::COPY_DST..hal::BufferUses::COPY_SRC,
+                }]);
+        }
+
+        let pending_writes = Mutex::new(
+            rank::QUEUE_PENDING_WRITES,
+            ManuallyDrop::new(pending_writes),
+        );
+
+        Ok(Queue {
             raw: ManuallyDrop::new(raw),
             device,
-        }
+            pending_writes,
+        })
     }
 
     pub(crate) fn raw(&self) -> &dyn hal::DynQueue {
@@ -70,6 +115,9 @@ crate::impl_storage_item!(Queue);
 impl Drop for Queue {
     fn drop(&mut self) {
         resource_log!("Drop {}", self.error_ident());
+        // SAFETY: We are in the Drop impl and we don't use self.pending_writes anymore after this point.
+        let pending_writes = unsafe { ManuallyDrop::take(&mut self.pending_writes.lock()) };
+        pending_writes.dispose(self.device.raw());
         // SAFETY: we never access `self.raw` beyond this point.
         let queue = unsafe { ManuallyDrop::take(&mut self.raw) };
         self.device.release_queue(queue);
@@ -418,7 +466,7 @@ impl Queue {
         // freed, even if an error occurs. All paths from here must call
         // `device.pending_writes.consume`.
         let mut staging_buffer = StagingBuffer::new(&self.device, data_size)?;
-        let mut pending_writes = self.device.pending_writes.lock();
+        let mut pending_writes = self.pending_writes.lock();
 
         let staging_buffer = {
             profiling::scope!("copy");
@@ -460,7 +508,7 @@ impl Queue {
 
         let buffer = buffer.get()?;
 
-        let mut pending_writes = self.device.pending_writes.lock();
+        let mut pending_writes = self.pending_writes.lock();
 
         // At this point, we have taken ownership of the staging_buffer from the
         // user. Platform validation requires that the staging buffer always
@@ -636,7 +684,7 @@ impl Queue {
                 .map_err(TransferError::from)?;
         }
 
-        let mut pending_writes = self.device.pending_writes.lock();
+        let mut pending_writes = self.pending_writes.lock();
         let encoder = pending_writes.activate();
 
         // If the copy does not fully cover the layers, we need to initialize to
@@ -888,7 +936,7 @@ impl Queue {
 
         let (selector, dst_base) = extract_texture_selector(&destination, &size, &dst)?;
 
-        let mut pending_writes = self.device.pending_writes.lock();
+        let mut pending_writes = self.pending_writes.lock();
         let encoder = pending_writes.activate();
 
         // If the copy does not fully cover the layers, we need to initialize to
@@ -1157,7 +1205,7 @@ impl Queue {
                 }
             }
 
-            let mut pending_writes = self.device.pending_writes.lock();
+            let mut pending_writes = self.pending_writes.lock();
 
             {
                 used_surface_textures.set_size(self.device.tracker_indices.textures.size());

wgpu-core/src/device/resource.rs

@@ -6,10 +6,8 @@ use crate::{
     device::{
         bgl, create_validator,
         life::{LifetimeTracker, WaitIdleError},
-        map_buffer,
-        queue::PendingWrites,
-        AttachmentData, DeviceLostInvocation, HostMap, MissingDownlevelFlags, MissingFeatures,
-        RenderPassContext, CLEANUP_WAIT_MS,
+        map_buffer, AttachmentData, DeviceLostInvocation, HostMap, MissingDownlevelFlags,
+        MissingFeatures, RenderPassContext, CLEANUP_WAIT_MS,
     },
     hal_label,
     init_tracker::{
@@ -141,7 +139,6 @@ pub struct Device {
     pub(crate) features: wgt::Features,
     pub(crate) downlevel: wgt::DownlevelCapabilities,
     pub(crate) instance_flags: wgt::InstanceFlags,
-    pub(crate) pending_writes: Mutex<ManuallyDrop<PendingWrites>>,
     pub(crate) deferred_destroy: Mutex<Vec<DeferredDestroy>>,
     pub(crate) usage_scopes: UsageScopePool,
     pub(crate) last_acceleration_structure_build_command_index: AtomicU64,
@@ -181,11 +178,8 @@ impl Drop for Device {
         let raw = unsafe { ManuallyDrop::take(&mut self.raw) };
         // SAFETY: We are in the Drop impl and we don't use self.zero_buffer anymore after this point.
         let zero_buffer = unsafe { ManuallyDrop::take(&mut self.zero_buffer) };
-        // SAFETY: We are in the Drop impl and we don't use self.pending_writes anymore after this point.
-        let pending_writes = unsafe { ManuallyDrop::take(&mut self.pending_writes.lock()) };
         // SAFETY: We are in the Drop impl and we don't use self.fence anymore after this point.
         let fence = unsafe { ManuallyDrop::take(&mut self.fence.write()) };
-        pending_writes.dispose(raw.as_ref());
         self.command_allocator.dispose(raw.as_ref());
         #[cfg(feature = "indirect-validation")]
         self.indirect_validation
@@ -228,7 +222,6 @@ impl Device {
 impl Device {
     pub(crate) fn new(
         raw_device: Box<dyn hal::DynDevice>,
-        raw_queue: &dyn hal::DynQueue,
         adapter: &Arc<Adapter>,
         desc: &DeviceDescriptor,
         trace_path: Option<&std::path::Path>,
@@ -241,10 +234,6 @@ impl Device {
         let fence = unsafe { raw_device.create_fence() }.map_err(DeviceError::from_hal)?;
 
         let command_allocator = command::CommandAllocator::new();
-        let pending_encoder = command_allocator
-            .acquire_encoder(raw_device.as_ref(), raw_queue)
-            .map_err(DeviceError::from_hal)?;
-        let mut pending_writes = PendingWrites::new(pending_encoder);
 
         // Create zeroed buffer used for texture clears.
         let zero_buffer = unsafe {
@@ -256,24 +245,6 @@ impl Device {
             })
         }
         .map_err(DeviceError::from_hal)?;
-        pending_writes.activate();
-        unsafe {
-            pending_writes
-                .command_encoder
-                .transition_buffers(&[hal::BufferBarrier {
-                    buffer: zero_buffer.as_ref(),
-                    usage: hal::BufferUses::empty()..hal::BufferUses::COPY_DST,
-                }]);
-            pending_writes
-                .command_encoder
-                .clear_buffer(zero_buffer.as_ref(), 0..ZERO_BUFFER_SIZE);
-            pending_writes
-                .command_encoder
-                .transition_buffers(&[hal::BufferBarrier {
-                    buffer: zero_buffer.as_ref(),
-                    usage: hal::BufferUses::COPY_DST..hal::BufferUses::COPY_SRC,
-                }]);
-        }
 
         let alignments = adapter.raw.capabilities.alignments.clone();
         let downlevel = adapter.raw.capabilities.downlevel.clone();
@@ -336,10 +307,6 @@ impl Device {
             features: desc.required_features,
             downlevel,
             instance_flags,
-            pending_writes: Mutex::new(
-                rank::DEVICE_PENDING_WRITES,
-                ManuallyDrop::new(pending_writes),
-            ),
             deferred_destroy: Mutex::new(rank::DEVICE_DEFERRED_DESTROY, Vec::new()),
             usage_scopes: Mutex::new(rank::DEVICE_USAGE_SCOPES, Default::default()),
             // By starting at one, we can put the result in a NonZeroU64.

wgpu-core/src/instance.rs

@@ -573,18 +573,14 @@ impl Adapter {
     ) -> Result<(Arc<Device>, Arc<Queue>), RequestDeviceError> {
         api_log!("Adapter::create_device");
 
-        let device = Device::new(
-            hal_device.device,
-            hal_device.queue.as_ref(),
-            self,
-            desc,
-            trace_path,
-            instance_flags,
-        )?;
-
+        let device = Device::new(hal_device.device, self, desc, trace_path, instance_flags)?;
         let device = Arc::new(device);
-        let queue = Arc::new(Queue::new(device.clone(), hal_device.queue));
+
+        let queue = Queue::new(device.clone(), hal_device.queue)?;
+        let queue = Arc::new(queue);
+
         device.set_queue(&queue);
+
         Ok((device, queue))
     }
 

wgpu-core/src/lock/rank.rs

@@ -111,11 +111,11 @@ define_lock_ranks! {
         // COMMAND_BUFFER_DATA,
     }
     rank BUFFER_MAP_STATE "Buffer::map_state" followed by {
-        DEVICE_PENDING_WRITES,
+        QUEUE_PENDING_WRITES,
         SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
         DEVICE_TRACE,
     }
-    rank DEVICE_PENDING_WRITES "Device::pending_writes" followed by {
+    rank QUEUE_PENDING_WRITES "Queue::pending_writes" followed by {
         COMMAND_ALLOCATOR_FREE_ENCODERS,
         SHARED_TRACKER_INDEX_ALLOCATOR_INNER,
         DEVICE_LIFE_TRACKER,

wgpu-core/src/resource.rs

@@ -676,10 +676,9 @@ impl Buffer {
                     });
                 }
 
-                let mut pending_writes = device.pending_writes.lock();
-
                 let staging_buffer = staging_buffer.flush();
 
+                if let Some(queue) = device.get_queue() {
                     let region = wgt::BufferSize::new(self.size).map(|size| hal::BufferCopy {
                         src_offset: 0,
                         dst_offset: 0,
@@ -693,6 +692,7 @@ impl Buffer {
                         buffer: raw_buf,
                         usage: hal::BufferUses::empty()..hal::BufferUses::COPY_DST,
                     };
+                    let mut pending_writes = queue.pending_writes.lock();
                     let encoder = pending_writes.activate();
                     unsafe {
                         encoder.transition_buffers(&[transition_src, transition_dst]);
@@ -707,6 +707,7 @@ impl Buffer {
                     pending_writes.consume(staging_buffer);
                     pending_writes.insert_buffer(self);
                 }
+            }
             BufferMapState::Idle => {
                 return Err(BufferAccessError::NotMapped);
             }
@@ -778,16 +779,19 @@ impl Buffer {
             })
         };
 
-        let mut pending_writes = device.pending_writes.lock();
+        if let Some(queue) = device.get_queue() {
+            let mut pending_writes = queue.pending_writes.lock();
             if pending_writes.contains_buffer(self) {
                 pending_writes.consume_temp(temp);
-        } else {
+                return Ok(());
+            }
+        }
+
         let mut life_lock = device.lock_life();
         let last_submit_index = life_lock.get_buffer_latest_submission_index(self);
         if let Some(last_submit_index) = last_submit_index {
             life_lock.schedule_resource_destruction(temp, last_submit_index);
         }
-        }
 
         Ok(())
     }
@@ -1244,16 +1248,19 @@ impl Texture {
             })
         };
 
-        let mut pending_writes = device.pending_writes.lock();
+        if let Some(queue) = device.get_queue() {
+            let mut pending_writes = queue.pending_writes.lock();
             if pending_writes.contains_texture(self) {
                 pending_writes.consume_temp(temp);
-        } else {
+                return Ok(());
+            }
+        }
+
         let mut life_lock = device.lock_life();
         let last_submit_index = life_lock.get_texture_latest_submission_index(self);
         if let Some(last_submit_index) = last_submit_index {
             life_lock.schedule_resource_destruction(temp, last_submit_index);
         }
-        }
 
         Ok(())
     }
@@ -1960,16 +1967,19 @@ impl Blas {
             })
         };
 
-        let mut pending_writes = device.pending_writes.lock();
+        if let Some(queue) = device.get_queue() {
+            let mut pending_writes = queue.pending_writes.lock();
             if pending_writes.contains_blas(self) {
                 pending_writes.consume_temp(temp);
-        } else {
+                return Ok(());
+            }
+        }
+
         let mut life_lock = device.lock_life();
         let last_submit_index = life_lock.get_blas_latest_submission_index(self);
         if let Some(last_submit_index) = last_submit_index {
             life_lock.schedule_resource_destruction(temp, last_submit_index);
         }
-        }
 
         Ok(())
     }
@@ -2047,16 +2057,19 @@ impl Tlas {
             })
         };
 
-        let mut pending_writes = device.pending_writes.lock();
+        if let Some(queue) = device.get_queue() {
+            let mut pending_writes = queue.pending_writes.lock();
             if pending_writes.contains_tlas(self) {
                 pending_writes.consume_temp(temp);
-        } else {
+                return Ok(());
+            }
+        }
+
         let mut life_lock = device.lock_life();
         let last_submit_index = life_lock.get_tlas_latest_submission_index(self);
         if let Some(last_submit_index) = last_submit_index {
             life_lock.schedule_resource_destruction(temp, last_submit_index);
         }
-        }
 
         Ok(())
     }