map buffers immediately in map_async if the Queue has been dropped

wgpu-core/src/device/life.rs

@@ -3,7 +3,7 @@ use crate::{
         queue::{EncoderInFlight, SubmittedWorkDoneClosure, TempResource},
         DeviceError,
     },
-    resource::{self, Buffer, Texture, Trackable},
+    resource::{Buffer, Texture, Trackable},
     snatch::SnatchGuard,
     SubmissionIndex,
 };
@@ -388,7 +388,6 @@ impl LifetimeTracker {
     #[must_use]
     pub(crate) fn handle_mapping(
         &mut self,
-        raw: &dyn hal::DynDevice,
         snatch_guard: &SnatchGuard,
     ) -> Vec<super::BufferMapPendingClosure> {
         if self.ready_to_map.is_empty() {
@@ -398,61 +397,10 @@ impl LifetimeTracker {
             Vec::with_capacity(self.ready_to_map.len());
 
         for buffer in self.ready_to_map.drain(..) {
-            // This _cannot_ be inlined into the match. If it is, the lock will be held
+            match buffer.map(snatch_guard) {
-            // open through the whole match, resulting in a deadlock when we try to re-lock
+                Some(cb) => pending_callbacks.push(cb),
-            // the buffer back to active.
+                None => continue,
-            let mapping = std::mem::replace(
+            }
-                &mut *buffer.map_state.lock(),
-                resource::BufferMapState::Idle,
-            );
-            let pending_mapping = match mapping {
-                resource::BufferMapState::Waiting(pending_mapping) => pending_mapping,
-                // Mapping cancelled
-                resource::BufferMapState::Idle => continue,
-                // Mapping queued at least twice by map -> unmap -> map
-                // and was already successfully mapped below
-                resource::BufferMapState::Active { .. } => {
-                    *buffer.map_state.lock() = mapping;
-                    continue;
-                }
-                _ => panic!("No pending mapping."),
-            };
-            let status = if pending_mapping.range.start != pending_mapping.range.end {
-                let host = pending_mapping.op.host;
-                let size = pending_mapping.range.end - pending_mapping.range.start;
-                match super::map_buffer(
-                    raw,
-                    &buffer,
-                    pending_mapping.range.start,
-                    size,
-                    host,
-                    snatch_guard,
-                ) {
-                    Ok(mapping) => {
-                        *buffer.map_state.lock() = resource::BufferMapState::Active {
-                            mapping,
-                            range: pending_mapping.range.clone(),
-                            host,
-                        };
-                        Ok(())
-                    }
-                    Err(e) => {
-                        log::error!("Mapping failed: {e}");
-                        Err(e)
-                    }
-                }
-            } else {
-                *buffer.map_state.lock() = resource::BufferMapState::Active {
-                    mapping: hal::BufferMapping {
-                        ptr: std::ptr::NonNull::dangling(),
-                        is_coherent: true,
-                    },
-                    range: pending_mapping.range,
-                    host: pending_mapping.op.host,
-                };
-                Ok(())
-            };
-            pending_callbacks.push((pending_mapping.op, status));
         }
         pending_callbacks
     }

wgpu-core/src/device/mod.rs

@@ -298,24 +298,25 @@ impl DeviceLostClosure {
     }
 }
 
-fn map_buffer(
+pub(crate) fn map_buffer(
-    raw: &dyn hal::DynDevice,
     buffer: &Buffer,
     offset: BufferAddress,
     size: BufferAddress,
     kind: HostMap,
     snatch_guard: &SnatchGuard,
 ) -> Result<hal::BufferMapping, BufferAccessError> {
+    let raw_device = buffer.device.raw();
     let raw_buffer = buffer.try_raw(snatch_guard)?;
     let mapping = unsafe {
-        raw.map_buffer(raw_buffer, offset..offset + size)
+        raw_device
+            .map_buffer(raw_buffer, offset..offset + size)
             .map_err(|e| buffer.device.handle_hal_error(e))?
     };
 
     if !mapping.is_coherent && kind == HostMap::Read {
         #[allow(clippy::single_range_in_vec_init)]
         unsafe {
-            raw.invalidate_mapped_ranges(raw_buffer, &[offset..offset + size]);
+            raw_device.invalidate_mapped_ranges(raw_buffer, &[offset..offset + size]);
         }
     }
 
@@ -370,7 +371,7 @@ fn map_buffer(
                 && kind == HostMap::Read
                 && buffer.usage.contains(wgt::BufferUsages::MAP_WRITE)
             {
-                unsafe { raw.flush_mapped_ranges(raw_buffer, &[uninitialized]) };
+                unsafe { raw_device.flush_mapped_ranges(raw_buffer, &[uninitialized]) };
             }
         }
     }

wgpu-core/src/device/resource.rs

@@ -447,7 +447,7 @@ impl Device {
                 let submission_closures =
                     life_tracker.triage_submissions(submission_index, &self.command_allocator);
 
-                let mapping_closures = life_tracker.handle_mapping(self.raw(), &snatch_guard);
+                let mapping_closures = life_tracker.handle_mapping(&snatch_guard);
 
                 let queue_empty = life_tracker.queue_empty();
 
@@ -620,14 +620,7 @@ impl Device {
                 }
             } else {
                 let snatch_guard: SnatchGuard = self.snatchable_lock.read();
-                map_buffer(
+                map_buffer(&buffer, 0, map_size, HostMap::Write, &snatch_guard)?
-                    self.raw(),
-                    &buffer,
-                    0,
-                    map_size,
-                    HostMap::Write,
-                    &snatch_guard,
-                )?
             };
             *buffer.map_state.lock() = resource::BufferMapState::Active {
                 mapping,

wgpu-core/src/resource.rs

@@ -637,13 +637,73 @@ impl Buffer {
         let submit_index = if let Some(queue) = device.get_queue() {
             queue.lock_life().map(self).unwrap_or(0) // '0' means no wait is necessary
         } else {
-            // TODO: map immediately
+            // We can safely unwrap below since we just set the `map_state` to `BufferMapState::Waiting`.
+            let (mut operation, status) = self.map(&device.snatchable_lock.read()).unwrap();
+            if let Some(callback) = operation.callback.take() {
+                callback.call(status);
+            }
             0
         };
 
         Ok(submit_index)
     }
 
+    /// This function returns [`None`] only if [`Self::map_state`] is not [`BufferMapState::Waiting`].
+    #[must_use]
+    pub(crate) fn map(&self, snatch_guard: &SnatchGuard) -> Option<BufferMapPendingClosure> {
+        // This _cannot_ be inlined into the match. If it is, the lock will be held
+        // open through the whole match, resulting in a deadlock when we try to re-lock
+        // the buffer back to active.
+        let mapping = mem::replace(&mut *self.map_state.lock(), BufferMapState::Idle);
+        let pending_mapping = match mapping {
+            BufferMapState::Waiting(pending_mapping) => pending_mapping,
+            // Mapping cancelled
+            BufferMapState::Idle => return None,
+            // Mapping queued at least twice by map -> unmap -> map
+            // and was already successfully mapped below
+            BufferMapState::Active { .. } => {
+                *self.map_state.lock() = mapping;
+                return None;
+            }
+            _ => panic!("No pending mapping."),
+        };
+        let status = if pending_mapping.range.start != pending_mapping.range.end {
+            let host = pending_mapping.op.host;
+            let size = pending_mapping.range.end - pending_mapping.range.start;
+            match crate::device::map_buffer(
+                self,
+                pending_mapping.range.start,
+                size,
+                host,
+                snatch_guard,
+            ) {
+                Ok(mapping) => {
+                    *self.map_state.lock() = BufferMapState::Active {
+                        mapping,
+                        range: pending_mapping.range.clone(),
+                        host,
+                    };
+                    Ok(())
+                }
+                Err(e) => {
+                    log::error!("Mapping failed: {e}");
+                    Err(e)
+                }
+            }
+        } else {
+            *self.map_state.lock() = BufferMapState::Active {
+                mapping: hal::BufferMapping {
+                    ptr: NonNull::dangling(),
+                    is_coherent: true,
+                },
+                range: pending_mapping.range,
+                host: pending_mapping.op.host,
+            };
+            Ok(())
+        };
+        Some((pending_mapping.op, status))
+    }
+
     // Note: This must not be called while holding a lock.
     pub(crate) fn unmap(
         self: &Arc<Self>,