Descriptor set allocator API 2.0 (#2400)

* Make `DescriptorSetAllocator` object-safe, remove the generics

* Fix tests

* Fix examples

* Fix docs

* Avoid panics in `deallocate`

* Typo

* Clarify docs

* Clarify safety preconditions of `allocate`

* Remove unnecessary `Arc` clone

* Tidy up a little

* Debug assert

examples/async-update/main.rs

@@ -476,8 +476,10 @@ fn main() -> Result<(), impl Error> {
     };
     let mut framebuffers = window_size_dependent_setup(&images, render_pass.clone(), &mut viewport);
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
 
     // A byproduct of always using the same set of uniform buffers is that we can also create one
     // descriptor set for each, reusing them in the same way as the buffers.
@@ -485,7 +487,7 @@ fn main() -> Result<(), impl Error> {
         .iter()
         .map(|buffer| {
             PersistentDescriptorSet::new(
-                &descriptor_set_allocator,
+                descriptor_set_allocator.clone(),
                 pipeline.layout().set_layouts()[0].clone(),
                 [WriteDescriptorSet::buffer(0, buffer.clone())],
                 [],
@@ -498,7 +500,7 @@ fn main() -> Result<(), impl Error> {
     let sampler = Sampler::new(device.clone(), SamplerCreateInfo::simple_repeat_linear()).unwrap();
     let sampler_sets = textures.map(|texture| {
         PersistentDescriptorSet::new(
-            &descriptor_set_allocator,
+            descriptor_set_allocator.clone(),
             pipeline.layout().set_layouts()[1].clone(),
             [
                 WriteDescriptorSet::sampler(0, sampler.clone()),

examples/basic-compute-shader/main.rs

@@ -151,8 +151,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -183,7 +185,7 @@ fn main() {
     // descriptor sets that each contain the buffer you want to run the shader on.
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::buffer(0, data_buffer.clone())],
         [],

examples/deferred/frame/ambient_lighting_system.rs

@@ -169,7 +169,7 @@ impl AmbientLightingSystem {
 
         let layout = self.pipeline.layout().set_layouts().get(0).unwrap();
         let descriptor_set = PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             layout.clone(),
             [WriteDescriptorSet::image_view(0, color_input)],
             [],

examples/deferred/frame/directional_lighting_system.rs

@@ -180,7 +180,7 @@ impl DirectionalLightingSystem {
 
         let layout = self.pipeline.layout().set_layouts().get(0).unwrap();
         let descriptor_set = PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             layout.clone(),
             [
                 WriteDescriptorSet::image_view(0, color_input),

examples/deferred/frame/point_lighting_system.rs

@@ -192,7 +192,7 @@ impl PointLightingSystem {
 
         let layout = self.pipeline.layout().set_layouts().get(0).unwrap();
         let descriptor_set = PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             layout.clone(),
             [
                 WriteDescriptorSet::image_view(0, color_input),

examples/dynamic-buffers/main.rs

@@ -145,8 +145,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -211,7 +213,7 @@ fn main() {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [
             // When writing to the dynamic buffer binding, the range of the buffer that the shader

examples/dynamic-local-size/main.rs

@@ -202,8 +202,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -223,7 +225,7 @@ fn main() {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::image_view(0, view)],
         [],

examples/gl-interop/main.rs

@@ -269,15 +269,17 @@ mod linux {
             }
         });
 
-        let descriptor_set_allocator =
-            StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+        let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+            device.clone(),
+            Default::default(),
+        ));
         let command_buffer_allocator =
             StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
         let layout = pipeline.layout().set_layouts().get(0).unwrap();
 
         let set = PersistentDescriptorSet::new(
-            &descriptor_set_allocator,
+            descriptor_set_allocator,
             layout.clone(),
             [
                 WriteDescriptorSet::sampler(0, sampler),

examples/image-self-copy-blit/main.rs

@@ -201,8 +201,10 @@ fn main() -> Result<(), impl Error> {
     )
     .unwrap();
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
     let mut uploads = AutoCommandBufferBuilder::primary(
@@ -379,7 +381,7 @@ fn main() -> Result<(), impl Error> {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [
             WriteDescriptorSet::sampler(0, sampler),

examples/image/main.rs

@@ -201,8 +201,10 @@ fn main() -> Result<(), impl Error> {
     )
     .unwrap();
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
     let mut uploads = AutoCommandBufferBuilder::primary(
@@ -327,7 +329,7 @@ fn main() -> Result<(), impl Error> {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [
             WriteDescriptorSet::sampler(0, sampler),

examples/immutable-sampler/main.rs

@@ -207,8 +207,10 @@ fn main() -> Result<(), impl Error> {
     )
     .unwrap();
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
     let mut uploads = AutoCommandBufferBuilder::primary(
@@ -348,7 +350,7 @@ fn main() -> Result<(), impl Error> {
     // Use `image_view` instead of `image_view_sampler`, since the sampler is already in the
     // layout.
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::image_view(1, texture)],
         [],

examples/indirect/main.rs

@@ -361,8 +361,10 @@ fn main() -> Result<(), impl Error> {
     let mut recreate_swapchain = false;
     let mut previous_frame_end = Some(sync::now(device.clone()).boxed());
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -453,7 +455,7 @@ fn main() -> Result<(), impl Error> {
                 // Pass the two buffers to the compute shader.
                 let layout = compute_pipeline.layout().set_layouts().get(0).unwrap();
                 let cs_desciptor_set = PersistentDescriptorSet::new(
-                    &descriptor_set_allocator,
+                    descriptor_set_allocator.clone(),
                     layout.clone(),
                     [
                         WriteDescriptorSet::buffer(0, vertices.clone()),

examples/interactive-fractal/fractal_compute_pipeline.rs

@@ -139,7 +139,7 @@ impl FractalComputePipeline {
         let pipeline_layout = self.pipeline.layout();
         let desc_layout = pipeline_layout.set_layouts().get(0).unwrap();
         let set = PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             desc_layout.clone(),
             [
                 WriteDescriptorSet::image_view(0, image_view),

examples/interactive-fractal/pixels_draw_pipeline.rs

@@ -187,7 +187,7 @@ impl PixelsDrawPipeline {
         .unwrap();
 
         PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             layout.clone(),
             [
                 WriteDescriptorSet::sampler(0, sampler),

examples/multi-window-game-of-life/game_of_life.rs

@@ -174,7 +174,7 @@ impl GameOfLifeComputePipeline {
         let pipeline_layout = self.compute_life_pipeline.layout();
         let desc_layout = pipeline_layout.set_layouts().get(0).unwrap();
         let set = PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             desc_layout.clone(),
             [
                 WriteDescriptorSet::image_view(0, self.image.clone()),

examples/multi-window-game-of-life/pixels_draw.rs

@@ -183,7 +183,7 @@ impl PixelsDrawPipeline {
         .unwrap();
 
         PersistentDescriptorSet::new(
-            &self.descriptor_set_allocator,
+            self.descriptor_set_allocator.clone(),
             layout.clone(),
             [
                 WriteDescriptorSet::sampler(0, sampler),

examples/push-constants/main.rs

@@ -133,8 +133,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -155,7 +157,7 @@ fn main() {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::buffer(0, data_buffer.clone())],
         [],

examples/runtime-array/main.rs

@@ -261,8 +261,10 @@ fn main() -> Result<(), impl Error> {
     )
     .unwrap();
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
     let mut uploads = AutoCommandBufferBuilder::primary(
@@ -447,7 +449,7 @@ fn main() -> Result<(), impl Error> {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new_variable(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         2,
         [

examples/self-copy-buffer/main.rs

@@ -125,8 +125,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -151,7 +153,7 @@ fn main() {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::buffer(0, data_buffer.clone())],
         [],

examples/shader-include/main.rs

@@ -133,8 +133,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -155,7 +157,7 @@ fn main() {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::buffer(0, data_buffer.clone())],
         [],

examples/shader-types-sharing/main.rs

@@ -181,7 +181,7 @@ fn main() {
         data_buffer: Subbuffer<[u32]>,
         parameters: shaders::Parameters,
         command_buffer_allocator: &StandardCommandBufferAllocator,
-        descriptor_set_allocator: &StandardDescriptorSetAllocator,
+        descriptor_set_allocator: Arc<StandardDescriptorSetAllocator>,
     ) {
         let layout = pipeline.layout().set_layouts().get(0).unwrap();
         let set = PersistentDescriptorSet::new(
@@ -226,8 +226,10 @@ fn main() {
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
 
     // Prepare test array `[0, 1, 2, 3....]`.
     let data_buffer = Buffer::from_iter(
@@ -300,7 +302,7 @@ fn main() {
         data_buffer.clone(),
         shaders::Parameters { value: 2 },
         &command_buffer_allocator,
-        &descriptor_set_allocator,
+        descriptor_set_allocator.clone(),
     );
 
     // Then add 1 to each value.
@@ -310,7 +312,7 @@ fn main() {
         data_buffer.clone(),
         shaders::Parameters { value: 1 },
         &command_buffer_allocator,
-        &descriptor_set_allocator,
+        descriptor_set_allocator.clone(),
     );
 
     // Then multiply each value by 3.
@@ -320,7 +322,7 @@ fn main() {
         data_buffer.clone(),
         shaders::Parameters { value: 3 },
         &command_buffer_allocator,
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
     );
 
     let data_buffer_content = data_buffer.read().unwrap();

examples/simple-particles/main.rs

@@ -318,8 +318,10 @@ fn main() -> Result<(), impl Error> {
     }
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -431,7 +433,7 @@ fn main() -> Result<(), impl Error> {
     // Create a new descriptor set for binding vertices as a storage buffer.
     use vulkano::pipeline::Pipeline; // Required to access the `layout` method of pipeline.
     let descriptor_set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator.clone(),
         compute_pipeline
             .layout()
             .set_layouts()

examples/specialization-constants/main.rs

@@ -134,8 +134,10 @@ fn main() {
     };
 
     let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -156,7 +158,7 @@ fn main() {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [WriteDescriptorSet::buffer(0, data_buffer.clone())],
         [],

examples/teapot/main.rs

@@ -251,8 +251,10 @@ fn main() -> Result<(), impl Error> {
     let mut previous_frame_end = Some(sync::now(device.clone()).boxed());
     let rotation_start = Instant::now();
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
 
@@ -340,7 +342,7 @@ fn main() -> Result<(), impl Error> {
 
                 let layout = pipeline.layout().set_layouts().get(0).unwrap();
                 let set = PersistentDescriptorSet::new(
-                    &descriptor_set_allocator,
+                    descriptor_set_allocator.clone(),
                     layout.clone(),
                     [WriteDescriptorSet::buffer(0, uniform_buffer_subbuffer)],
                     [],

examples/texture-array/main.rs

@@ -203,8 +203,10 @@ fn main() -> Result<(), impl Error> {
     )
     .unwrap();
 
-    let descriptor_set_allocator =
-        StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+    let descriptor_set_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+        device.clone(),
+        Default::default(),
+    ));
     let command_buffer_allocator =
         StandardCommandBufferAllocator::new(device.clone(), Default::default());
     let mut uploads = AutoCommandBufferBuilder::primary(
@@ -338,7 +340,7 @@ fn main() -> Result<(), impl Error> {
 
     let layout = pipeline.layout().set_layouts().get(0).unwrap();
     let set = PersistentDescriptorSet::new(
-        &descriptor_set_allocator,
+        descriptor_set_allocator,
         layout.clone(),
         [
             WriteDescriptorSet::sampler(0, sampler),

vulkano/src/command_buffer/auto/mod.rs

@@ -780,11 +780,13 @@ mod tests {
             )
             .unwrap();
 
-            let ds_allocator =
-                StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+            let ds_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+                device.clone(),
+                Default::default(),
+            ));
 
             let set = PersistentDescriptorSet::new(
-                &ds_allocator,
+                ds_allocator.clone(),
                 set_layout.clone(),
                 [WriteDescriptorSet::sampler(
                     0,
@@ -855,7 +857,7 @@ mod tests {
             .unwrap();
 
             let set = PersistentDescriptorSet::new(
-                &ds_allocator,
+                ds_allocator.clone(),
                 set_layout,
                 [WriteDescriptorSet::sampler(
                     0,

vulkano/src/descriptor_set/allocator.rs

@@ -22,7 +22,14 @@ use crate::{
     Validated, VulkanError,
 };
 use crossbeam_queue::ArrayQueue;
-use std::{cell::UnsafeCell, mem::ManuallyDrop, num::NonZeroU64, sync::Arc, thread};
+use std::{
+    cell::UnsafeCell,
+    fmt::{Debug, Error as FmtError, Formatter},
+    mem,
+    num::NonZeroU64,
+    ptr,
+    sync::Arc,
+};
 use thread_local::ThreadLocal;
 
 const MAX_POOLS: usize = 32;
@@ -31,36 +38,121 @@ const MAX_POOLS: usize = 32;
 ///
 /// # Safety
 ///
-/// A Vulkan descriptor pool must be externally synchronized as if it owned the descriptor sets that
-/// were allocated from it. This includes allocating from the pool, freeing from the pool and
-/// resetting the pool or individual descriptor sets. The implementation of `DescriptorSetAllocator`
-/// is expected to manage this.
+/// A Vulkan descriptor pool must be externally synchronized as if it owned the descriptor sets
+/// that were allocated from it. This includes allocating from the pool, freeing from the pool and
+/// resetting the pool. The implementation of `DescriptorSetAllocator` is expected to manage this.
 ///
-/// The destructor of the [`DescriptorSetAlloc`] is expected to free the descriptor set, reset the
-/// descriptor set, or add it to a pool so that it gets reused. If the implementation frees or
-/// resets the descriptor set, it must not forget that this operation must be externally
-/// synchronized.
-pub unsafe trait DescriptorSetAllocator: DeviceOwned {
-    /// Object that represented an allocated descriptor set.
-    ///
-    /// The destructor of this object should free the descriptor set.
-    type Alloc: DescriptorSetAlloc;
-
+/// The implementation of `allocate` must return a valid allocation that stays allocated until
+/// either `deallocate` is called on it or the allocator is dropped. If the allocator is cloned, it
+/// must produce the same allocator, and an allocation must stay allocated until either
+/// `deallocate` is called on any of the clones or all clones have been dropped.
+///
+/// The implementation of `deallocate` is expected to free the descriptor set, reset its descriptor
+/// pool, or add it to a pool so that it gets reused. If the implementation frees the descriptor
+/// set or resets the descriptor pool, it must not forget that this operation must be externally
+/// synchronized. The implementation should not panic as it is used while dropping descriptor sets.
+pub unsafe trait DescriptorSetAllocator: DeviceOwned + Send + Sync + 'static {
     /// Allocates a descriptor set.
     fn allocate(
         &self,
         layout: &Arc<DescriptorSetLayout>,
         variable_descriptor_count: u32,
-    ) -> Result<Self::Alloc, Validated<VulkanError>>;
+    ) -> Result<DescriptorSetAlloc, Validated<VulkanError>>;
+
+    /// Deallocates the given `allocation`.
+    ///
+    /// # Safety
+    ///
+    /// - `allocation` must refer to a **currently allocated** allocation of `self`.
+    unsafe fn deallocate(&self, allocation: DescriptorSetAlloc);
 }
 
-/// An allocated descriptor set.
-pub trait DescriptorSetAlloc: Send + Sync {
-    /// Returns the internal object that contains the descriptor set.
-    fn inner(&self) -> &DescriptorPoolAlloc;
+impl Debug for dyn DescriptorSetAllocator {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
+        f.debug_struct("DescriptorSetAllocator")
+            .finish_non_exhaustive()
+    }
+}
 
-    /// Returns the descriptor pool that the descriptor set was allocated from.
-    fn pool(&self) -> &DescriptorPool;
+/// An allocation made using a [descriptor set allocator].
+///
+/// [descriptor set allocator]: DescriptorSetAllocator
+#[derive(Debug)]
+pub struct DescriptorSetAlloc {
+    /// The internal object that contains the descriptor set.
+    pub inner: DescriptorPoolAlloc,
+
+    /// The descriptor pool that the descriptor set was allocated from.
+    ///
+    /// Using this for anything other than looking at the pool's metadata will lead to a Bad
+    /// Time<sup>TM</sup>. That includes making additional references.
+    pub pool: Arc<DescriptorPool>,
+
+    /// An opaque handle identifying the allocation inside the allocator.
+    pub handle: AllocationHandle,
+}
+
+unsafe impl Send for DescriptorSetAlloc {}
+unsafe impl Sync for DescriptorSetAlloc {}
+
+/// An opaque handle identifying an allocation inside an allocator.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+#[cfg_attr(not(doc), repr(transparent))]
+pub struct AllocationHandle(*mut ());
+
+unsafe impl Send for AllocationHandle {}
+unsafe impl Sync for AllocationHandle {}
+
+impl AllocationHandle {
+    /// Creates a null `AllocationHandle`.
+    ///
+    /// Use this if you don't have anything that you need to associate with the allocation.
+    #[inline]
+    pub const fn null() -> Self {
+        AllocationHandle(ptr::null_mut())
+    }
+
+    /// Stores a pointer in an `AllocationHandle`.
+    ///
+    /// Use this if you want to associate an allocation with some (host) heap allocation.
+    #[inline]
+    pub const fn from_ptr(ptr: *mut ()) -> Self {
+        AllocationHandle(ptr)
+    }
+
+    /// Stores an index inside an `AllocationHandle`.
+    ///
+    /// Use this if you want to associate an allocation with some index.
+    #[allow(clippy::useless_transmute)]
+    #[inline]
+    pub const fn from_index(index: usize) -> Self {
+        // SAFETY: `usize` and `*mut ()` have the same layout.
+        AllocationHandle(unsafe { mem::transmute::<usize, *mut ()>(index) })
+    }
+
+    /// Retrieves a previously-stored pointer from the `AllocationHandle`.
+    ///
+    /// If this handle hasn't been created using [`from_ptr`] then this will return an invalid
+    /// pointer, dereferencing which is undefined behavior.
+    ///
+    /// [`from_ptr`]: Self::from_ptr
+    #[inline]
+    pub const fn as_ptr(self) -> *mut () {
+        self.0
+    }
+
+    /// Retrieves a previously-stored index from the `AllocationHandle`.
+    ///
+    /// If this handle hasn't been created using [`from_index`] then this will return a bogus
+    /// result.
+    ///
+    /// [`from_index`]: Self::from_index
+    #[allow(clippy::transmutes_expressible_as_ptr_casts)]
+    #[inline]
+    pub const fn as_index(self) -> usize {
+        // SAFETY: `usize` and `*mut ()` have the same layout.
+        unsafe { mem::transmute::<*mut (), usize>(self.0) }
+    }
 }
 
 /// Standard implementation of a descriptor set allocator.
@@ -135,44 +227,87 @@ impl StandardDescriptorSetAllocator {
 }
 
 unsafe impl DescriptorSetAllocator for StandardDescriptorSetAllocator {
-    type Alloc = StandardDescriptorSetAlloc;
-
-    /// Allocates a descriptor set.
     #[inline]
     fn allocate(
         &self,
         layout: &Arc<DescriptorSetLayout>,
         variable_descriptor_count: u32,
-    ) -> Result<StandardDescriptorSetAlloc, Validated<VulkanError>> {
-        let max_count = layout.variable_descriptor_count();
-        let pools = self.pools.get_or(Default::default);
+    ) -> Result<DescriptorSetAlloc, Validated<VulkanError>> {
+        let is_fixed = layout.variable_descriptor_count() == 0;
+        let pools = self.pools.get_or_default();
 
         let entry = unsafe { &mut *pools.get() }.get_or_try_insert(layout.id(), || {
-            if max_count == 0 {
-                FixedEntry::new(layout.clone(), &self.create_info).map(Entry::Fixed)
+            if is_fixed {
+                FixedEntry::new(layout, &self.create_info).map(Entry::Fixed)
             } else {
-                VariableEntry::new(layout.clone(), &self.create_info).map(Entry::Variable)
+                VariableEntry::new(
+                    layout,
+                    &self.create_info,
+                    Arc::new(ArrayQueue::new(MAX_POOLS)),
+                )
+                .map(Entry::Variable)
             }
         })?;
 
         match entry {
-            Entry::Fixed(entry) => entry.allocate(&self.create_info),
-            Entry::Variable(entry) => entry.allocate(variable_descriptor_count, &self.create_info),
+            Entry::Fixed(entry) => entry.allocate(layout, &self.create_info),
+            Entry::Variable(entry) => {
+                entry.allocate(layout, variable_descriptor_count, &self.create_info)
+            }
+        }
+    }
+
+    #[inline]
+    unsafe fn deallocate(&self, allocation: DescriptorSetAlloc) {
+        let is_fixed = allocation.inner.variable_descriptor_count() == 0;
+        let ptr = allocation.handle.as_ptr();
+
+        if is_fixed {
+            // SAFETY: The caller must guarantee that `allocation` refers to one allocated by
+            // `self`, therefore `ptr` must be the same one we gave out on allocation. We also know
+            // that the pointer must be valid, because the caller must guarantee that the same
+            // allocation isn't deallocated more than once. That means that since we cloned the
+            // `Arc` on allocation, at least that strong reference must still keep it alive, and we
+            // can safely drop this clone at the end of the scope here.
+            let reserve = unsafe { Arc::from_raw(ptr.cast::<ArrayQueue<DescriptorPoolAlloc>>()) };
+
+            // This cannot happen because every allocation is (supposed to be) returned to the pool
+            // whence it came, so there must be enough room for it.
+            debug_assert!(reserve.push(allocation.inner).is_ok());
+        } else {
+            // SAFETY: Same as the `Arc::from_raw` above.
+            let reserve = unsafe { Arc::from_raw(ptr.cast::<ArrayQueue<Arc<DescriptorPool>>>()) };
+
+            let pool = allocation.pool;
+
+            // We have to make sure that we only reset the pool under this condition, because there
+            // could be other references in other allocations. If the user cloned the pool
+            // themself, that will most certainly cause a leak.
+            if Arc::strong_count(&pool) == 1 {
+                // If there is not enough space in the reserve, we destroy the pool. The only way
+                // this can happen is if something is resource hogging, forcing new pools to be
+                // created such that the number exceeds `MAX_POOLS`, and then drops them all at
+                // once.
+                let _ = reserve.push(pool);
+            }
         }
     }
 }
 
 unsafe impl<T: DescriptorSetAllocator> DescriptorSetAllocator for Arc<T> {
-    type Alloc = T::Alloc;
-
     #[inline]
     fn allocate(
         &self,
         layout: &Arc<DescriptorSetLayout>,
         variable_descriptor_count: u32,
-    ) -> Result<Self::Alloc, Validated<VulkanError>> {
+    ) -> Result<DescriptorSetAlloc, Validated<VulkanError>> {
         (**self).allocate(layout, variable_descriptor_count)
     }
+
+    #[inline]
+    unsafe fn deallocate(&self, allocation: DescriptorSetAlloc) {
+        (**self).deallocate(allocation)
+    }
 }
 
 unsafe impl DeviceOwned for StandardDescriptorSetAllocator {
@@ -184,59 +319,16 @@ unsafe impl DeviceOwned for StandardDescriptorSetAllocator {
 
 #[derive(Debug)]
 struct FixedEntry {
-    // The `FixedPool` struct contains an actual Vulkan pool. Every time it is full we create
-    // a new pool and replace the current one with the new one.
-    pool: Arc<FixedPool>,
-    // The descriptor set layout that this pool is for.
-    layout: Arc<DescriptorSetLayout>,
+    pool: Arc<DescriptorPool>,
+    reserve: Arc<ArrayQueue<DescriptorPoolAlloc>>,
 }
 
 impl FixedEntry {
-    fn new(
-        layout: Arc<DescriptorSetLayout>,
-        create_info: &StandardDescriptorSetAllocatorCreateInfo,
-    ) -> Result<Self, Validated<VulkanError>> {
-        Ok(FixedEntry {
-            pool: FixedPool::new(&layout, create_info)?,
-            layout,
-        })
-    }
-
-    fn allocate(
-        &mut self,
-        create_info: &StandardDescriptorSetAllocatorCreateInfo,
-    ) -> Result<StandardDescriptorSetAlloc, Validated<VulkanError>> {
-        let inner = if let Some(inner) = self.pool.reserve.pop() {
-            inner
-        } else {
-            self.pool = FixedPool::new(&self.layout, create_info)?;
-
-            self.pool.reserve.pop().unwrap()
-        };
-
-        Ok(StandardDescriptorSetAlloc {
-            inner: ManuallyDrop::new(inner),
-            parent: AllocParent::Fixed(self.pool.clone()),
-        })
-    }
-}
-
-#[derive(Debug)]
-struct FixedPool {
-    // The actual Vulkan descriptor pool. This field isn't actually used anywhere, but we need to
-    // keep the pool alive in order to keep the descriptor sets valid.
-    inner: DescriptorPool,
-    // List of descriptor sets. When `alloc` is called, a descriptor will be extracted from this
-    // list. When a `SingleLayoutPoolAlloc` is dropped, its descriptor set is put back in this list.
-    reserve: ArrayQueue<DescriptorPoolAlloc>,
-}
-
-impl FixedPool {
     fn new(
         layout: &Arc<DescriptorSetLayout>,
         create_info: &StandardDescriptorSetAllocatorCreateInfo,
-    ) -> Result<Arc<Self>, Validated<VulkanError>> {
-        let inner = DescriptorPool::new(
+    ) -> Result<Self, Validated<VulkanError>> {
+        let pool = DescriptorPool::new(
             layout.device().clone(),
             DescriptorPoolCreateInfo {
                 flags: create_info
@@ -260,135 +352,68 @@ impl FixedPool {
         let allocate_infos =
             (0..create_info.set_count).map(|_| DescriptorSetAllocateInfo::new(layout.clone()));
 
-        let allocs = unsafe {
-            inner
-                .allocate_descriptor_sets(allocate_infos)
-                .map_err(|err| match err {
+        let allocs =
+            unsafe { pool.allocate_descriptor_sets(allocate_infos) }.map_err(|err| match err {
                 Validated::ValidationError(_) => err,
                 Validated::Error(vk_err) => match vk_err {
                     VulkanError::OutOfHostMemory | VulkanError::OutOfDeviceMemory => err,
-                        VulkanError::FragmentedPool => {
                     // This can't happen as we don't free individual sets.
-                            unreachable!();
-                        }
-                        VulkanError::OutOfPoolMemory => {
+                    VulkanError::FragmentedPool => unreachable!(),
                     // We created the pool with an exact size.
-                            unreachable!();
-                        }
-                        _ => {
+                    VulkanError::OutOfPoolMemory => unreachable!(),
                     // Shouldn't ever be returned.
-                            unreachable!();
-                        }
+                    _ => unreachable!(),
                 },
-                })?
-        };
+            })?;
 
         let reserve = ArrayQueue::new(create_info.set_count);
+
         for alloc in allocs {
             let _ = reserve.push(alloc);
         }
 
-        Ok(Arc::new(FixedPool { inner, reserve }))
+        Ok(FixedEntry {
+            pool: Arc::new(pool),
+            reserve: Arc::new(reserve),
+        })
+    }
+
+    fn allocate(
+        &mut self,
+        layout: &Arc<DescriptorSetLayout>,
+        create_info: &StandardDescriptorSetAllocatorCreateInfo,
+    ) -> Result<DescriptorSetAlloc, Validated<VulkanError>> {
+        let inner = if let Some(inner) = self.reserve.pop() {
+            inner
+        } else {
+            *self = FixedEntry::new(layout, create_info)?;
+
+            self.reserve.pop().unwrap()
+        };
+
+        Ok(DescriptorSetAlloc {
+            inner,
+            pool: self.pool.clone(),
+            handle: AllocationHandle::from_ptr(Arc::into_raw(self.reserve.clone()) as _),
+        })
     }
 }
 
 #[derive(Debug)]
 struct VariableEntry {
-    // The `VariablePool` struct contains an actual Vulkan pool. Every time it is full
-    // we grab one from the reserve, or create a new pool if there are none.
-    pool: Arc<VariablePool>,
-    // When a `VariablePool` is dropped, it returns its Vulkan pool here for reuse.
-    reserve: Arc<ArrayQueue<DescriptorPool>>,
-    // The descriptor set layout that this pool is for.
-    layout: Arc<DescriptorSetLayout>,
+    pool: Arc<DescriptorPool>,
+    reserve: Arc<ArrayQueue<Arc<DescriptorPool>>>,
     // The number of sets currently allocated from the Vulkan pool.
     allocations: usize,
 }
 
 impl VariableEntry {
     fn new(
-        layout: Arc<DescriptorSetLayout>,
+        layout: &DescriptorSetLayout,
         create_info: &StandardDescriptorSetAllocatorCreateInfo,
+        reserve: Arc<ArrayQueue<Arc<DescriptorPool>>>,
     ) -> Result<Self, Validated<VulkanError>> {
-        let reserve = Arc::new(ArrayQueue::new(MAX_POOLS));
-
-        Ok(VariableEntry {
-            pool: VariablePool::new(&layout, reserve.clone(), create_info)?,
-            reserve,
-            layout,
-            allocations: 0,
-        })
-    }
-
-    fn allocate(
-        &mut self,
-        variable_descriptor_count: u32,
-        create_info: &StandardDescriptorSetAllocatorCreateInfo,
-    ) -> Result<StandardDescriptorSetAlloc, Validated<VulkanError>> {
-        if self.allocations >= create_info.set_count {
-            self.pool = if let Some(inner) = self.reserve.pop() {
-                Arc::new(VariablePool {
-                    inner: ManuallyDrop::new(inner),
-                    reserve: self.reserve.clone(),
-                })
-            } else {
-                VariablePool::new(&self.layout, self.reserve.clone(), create_info)?
-            };
-            self.allocations = 0;
-        }
-
-        let allocate_info = DescriptorSetAllocateInfo {
-            variable_descriptor_count,
-            ..DescriptorSetAllocateInfo::new(self.layout.clone())
-        };
-
-        let mut sets = unsafe {
-            self.pool
-                .inner
-                .allocate_descriptor_sets([allocate_info])
-                .map_err(|err| match err {
-                    Validated::ValidationError(_) => err,
-                    Validated::Error(vk_err) => match vk_err {
-                        VulkanError::OutOfHostMemory | VulkanError::OutOfDeviceMemory => err,
-                        VulkanError::FragmentedPool => {
-                            // This can't happen as we don't free individual sets.
-                            unreachable!();
-                        }
-                        VulkanError::OutOfPoolMemory => {
-                            // We created the pool to fit the maximum variable descriptor count.
-                            unreachable!();
-                        }
-                        _ => {
-                            // Shouldn't ever be returned.
-                            unreachable!();
-                        }
-                    },
-                })?
-        };
-        self.allocations += 1;
-
-        Ok(StandardDescriptorSetAlloc {
-            inner: ManuallyDrop::new(sets.next().unwrap()),
-            parent: AllocParent::Variable(self.pool.clone()),
-        })
-    }
-}
-
-#[derive(Debug)]
-struct VariablePool {
-    // The actual Vulkan descriptor pool.
-    inner: ManuallyDrop<DescriptorPool>,
-    // Where we return the Vulkan descriptor pool in our `Drop` impl.
-    reserve: Arc<ArrayQueue<DescriptorPool>>,
-}
-
-impl VariablePool {
-    fn new(
-        layout: &Arc<DescriptorSetLayout>,
-        reserve: Arc<ArrayQueue<DescriptorPool>>,
-        create_info: &StandardDescriptorSetAllocatorCreateInfo,
-    ) -> Result<Arc<Self>, VulkanError> {
-        DescriptorPool::new(
+        let pool = DescriptorPool::new(
             layout.device().clone(),
             DescriptorPoolCreateInfo {
                 flags: create_info
@@ -407,30 +432,82 @@ impl VariablePool {
                 ..Default::default()
             },
         )
-        .map(|inner| {
-            Arc::new(Self {
-                inner: ManuallyDrop::new(inner),
+        .map_err(Validated::unwrap)?;
+
+        Ok(VariableEntry {
+            pool: Arc::new(pool),
             reserve,
+            allocations: 0,
         })
-        })
-        .map_err(Validated::unwrap)
-    }
-}
-
-impl Drop for VariablePool {
-    fn drop(&mut self) {
-        let inner = unsafe { ManuallyDrop::take(&mut self.inner) };
-
-        if thread::panicking() {
-            return;
     }
 
-        unsafe { inner.reset() }.unwrap();
+    fn allocate(
+        &mut self,
+        layout: &Arc<DescriptorSetLayout>,
+        variable_descriptor_count: u32,
+        create_info: &StandardDescriptorSetAllocatorCreateInfo,
+    ) -> Result<DescriptorSetAlloc, Validated<VulkanError>> {
+        if self.allocations >= create_info.set_count {
+            // This can happen if there's only ever one allocation alive at any point in time. In
+            // that case, when deallocating the last set before reaching `set_count`, there will be
+            // 2 references to the pool (one here and one in the allocation) and so the pool won't
+            // be returned to the reserve when deallocating. However, since there are no other
+            // allocations alive, there would be no other allocations that could return it to the
+            // reserve. To avoid dropping the pool unneccessarily, we simply continue using it. In
+            // the case where there are other references, we drop ours, at which point an
+            // allocation still holding a reference will be able to put the pool into the reserve
+            // when deallocated. If the user created a reference themself that will most certainly
+            // lead to a memory leak.
+            //
+            // TODO: This can still run into the A/B/A problem causing the pool to be dropped.
+            if Arc::strong_count(&self.pool) == 1 {
+                // SAFETY: We checked that the pool has a single strong reference above, meaning
+                // that all the allocations we gave out must have been deallocated.
+                unsafe { self.pool.reset() }?;
 
-        // If there is not enough space in the reserve, we destroy the pool. The only way this can
-        // happen is if something is resource hogging, forcing new pools to be created such that
-        // the number exceeds `MAX_POOLS`, and then drops them all at once.
-        let _ = self.reserve.push(inner);
+                self.allocations = 0;
+            } else {
+                if let Some(pool) = self.reserve.pop() {
+                    // SAFETY: We checked that the pool has a single strong reference when
+                    // deallocating, meaning that all the allocations we gave out must have been
+                    // deallocated.
+                    unsafe { pool.reset() }?;
+
+                    self.pool = pool;
+                    self.allocations = 0;
+                } else {
+                    *self = VariableEntry::new(layout, create_info, self.reserve.clone())?;
+                }
+            }
+        }
+
+        let allocate_info = DescriptorSetAllocateInfo {
+            variable_descriptor_count,
+            ..DescriptorSetAllocateInfo::new(layout.clone())
+        };
+
+        let mut sets = unsafe { self.pool.allocate_descriptor_sets([allocate_info]) }.map_err(
+            |err| match err {
+                Validated::ValidationError(_) => err,
+                Validated::Error(vk_err) => match vk_err {
+                    VulkanError::OutOfHostMemory | VulkanError::OutOfDeviceMemory => err,
+                    // This can't happen as we don't free individual sets.
+                    VulkanError::FragmentedPool => unreachable!(),
+                    // We created the pool to fit the maximum variable descriptor count.
+                    VulkanError::OutOfPoolMemory => unreachable!(),
+                    // Shouldn't ever be returned.
+                    _ => unreachable!(),
+                },
+            },
+        )?;
+
+        self.allocations += 1;
+
+        Ok(DescriptorSetAlloc {
+            inner: sets.next().unwrap(),
+            pool: self.pool.clone(),
+            handle: AllocationHandle::from_ptr(Arc::into_raw(self.reserve.clone()) as _),
+        })
     }
 }
 
@@ -475,63 +552,6 @@ impl Default for StandardDescriptorSetAllocatorCreateInfo {
     }
 }
 
-/// A descriptor set allocated from a [`StandardDescriptorSetAllocator`].
-#[derive(Debug)]
-pub struct StandardDescriptorSetAlloc {
-    // The actual descriptor set.
-    inner: ManuallyDrop<DescriptorPoolAlloc>,
-    // The pool where we allocated from. Needed for our `Drop` impl.
-    parent: AllocParent,
-}
-
-#[derive(Debug)]
-enum AllocParent {
-    Fixed(Arc<FixedPool>),
-    Variable(Arc<VariablePool>),
-}
-
-impl AllocParent {
-    #[inline]
-    fn pool(&self) -> &DescriptorPool {
-        match self {
-            Self::Fixed(pool) => &pool.inner,
-            Self::Variable(pool) => &pool.inner,
-        }
-    }
-}
-
-// This is needed because of the blanket impl of `Send` on `Arc<T>`, which requires that `T` is
-// `Send + Sync`. `FixedPool` and `VariablePool` are `Send + !Sync` because `DescriptorPool` is
-// `!Sync`. That's fine however because we never access the `DescriptorPool` concurrently.
-unsafe impl Send for StandardDescriptorSetAlloc {}
-unsafe impl Sync for StandardDescriptorSetAlloc {}
-
-impl DescriptorSetAlloc for StandardDescriptorSetAlloc {
-    #[inline]
-    fn inner(&self) -> &DescriptorPoolAlloc {
-        &self.inner
-    }
-
-    #[inline]
-    fn pool(&self) -> &DescriptorPool {
-        self.parent.pool()
-    }
-}
-
-impl Drop for StandardDescriptorSetAlloc {
-    #[inline]
-    fn drop(&mut self) {
-        let inner = unsafe { ManuallyDrop::take(&mut self.inner) };
-
-        match &self.parent {
-            AllocParent::Fixed(pool) => {
-                let _ = pool.reserve.push(inner);
-            }
-            AllocParent::Variable(_) => {}
-        }
-    }
-}
-
 mod sorted_map {
     use smallvec::SmallVec;
 
@@ -573,58 +593,3 @@ mod sorted_map {
         }
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::{
-        descriptor_set::layout::{
-            DescriptorSetLayoutBinding, DescriptorSetLayoutCreateInfo, DescriptorType,
-        },
-        shader::ShaderStages,
-        VulkanObject,
-    };
-    use std::thread;
-
-    #[test]
-    fn threads_use_different_pools() {
-        let (device, _) = gfx_dev_and_queue!();
-
-        let layout = DescriptorSetLayout::new(
-            device.clone(),
-            DescriptorSetLayoutCreateInfo {
-                bindings: [(
-                    0,
-                    DescriptorSetLayoutBinding {
-                        stages: ShaderStages::all_graphics(),
-                        ..DescriptorSetLayoutBinding::descriptor_type(DescriptorType::UniformBuffer)
-                    },
-                )]
-                .into(),
-                ..Default::default()
-            },
-        )
-        .unwrap();
-
-        let allocator = StandardDescriptorSetAllocator::new(device, Default::default());
-
-        let pool1 =
-            if let AllocParent::Fixed(pool) = &allocator.allocate(&layout, 0).unwrap().parent {
-                pool.inner.handle()
-            } else {
-                unreachable!()
-            };
-
-        thread::spawn(move || {
-            let pool2 =
-                if let AllocParent::Fixed(pool) = &allocator.allocate(&layout, 0).unwrap().parent {
-                    pool.inner.handle()
-                } else {
-                    unreachable!()
-                };
-            assert_ne!(pool1, pool2);
-        })
-        .join()
-        .unwrap();
-    }
-}

vulkano/src/descriptor_set/persistent.rs

@@ -19,9 +19,8 @@ use super::{
 };
 use crate::{
     descriptor_set::{
-        allocator::{DescriptorSetAlloc, DescriptorSetAllocator, StandardDescriptorSetAlloc},
-        update::WriteDescriptorSet,
-        DescriptorSet, DescriptorSetLayout, DescriptorSetResources,
+        allocator::DescriptorSetAllocator, update::WriteDescriptorSet, DescriptorSet,
+        DescriptorSetLayout, DescriptorSetResources,
     },
     device::{Device, DeviceOwned},
     Validated, ValidationError, VulkanError, VulkanObject,
@@ -33,8 +32,8 @@ use std::{
 };
 
 /// A simple, immutable descriptor set that is expected to be long-lived.
-pub struct PersistentDescriptorSet<P = StandardDescriptorSetAlloc> {
-    inner: UnsafeDescriptorSet<P>,
+pub struct PersistentDescriptorSet {
+    inner: UnsafeDescriptorSet,
     resources: DescriptorSetResources,
 }
 
@@ -43,15 +42,12 @@ impl PersistentDescriptorSet {
     ///
     /// See `new_with_pool` for more.
     #[inline]
-    pub fn new<A>(
-        allocator: &A,
+    pub fn new(
+        allocator: Arc<dyn DescriptorSetAllocator>,
         layout: Arc<DescriptorSetLayout>,
         descriptor_writes: impl IntoIterator<Item = WriteDescriptorSet>,
         descriptor_copies: impl IntoIterator<Item = CopyDescriptorSet>,
-    ) -> Result<Arc<PersistentDescriptorSet<A::Alloc>>, Validated<VulkanError>>
-    where
-        A: DescriptorSetAllocator + ?Sized,
-    {
+    ) -> Result<Arc<PersistentDescriptorSet>, Validated<VulkanError>> {
         Self::new_variable(allocator, layout, 0, descriptor_writes, descriptor_copies)
     }
 
@@ -62,16 +58,13 @@ impl PersistentDescriptorSet {
     ///
     /// - Panics if `layout` was created for push descriptors rather than descriptor sets.
     /// - Panics if `variable_descriptor_count` is too large for the given `layout`.
-    pub fn new_variable<A>(
-        allocator: &A,
+    pub fn new_variable(
+        allocator: Arc<dyn DescriptorSetAllocator>,
         layout: Arc<DescriptorSetLayout>,
         variable_descriptor_count: u32,
         descriptor_writes: impl IntoIterator<Item = WriteDescriptorSet>,
         descriptor_copies: impl IntoIterator<Item = CopyDescriptorSet>,
-    ) -> Result<Arc<PersistentDescriptorSet<A::Alloc>>, Validated<VulkanError>>
-    where
-        A: DescriptorSetAllocator + ?Sized,
-    {
+    ) -> Result<Arc<PersistentDescriptorSet>, Validated<VulkanError>> {
         let mut set = PersistentDescriptorSet {
             inner: UnsafeDescriptorSet::new(allocator, &layout, variable_descriptor_count)?,
             resources: DescriptorSetResources::new(&layout, variable_descriptor_count),
@@ -83,12 +76,7 @@ impl PersistentDescriptorSet {
 
         Ok(Arc::new(set))
     }
-}
 
-impl<P> PersistentDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
     unsafe fn update(
         &mut self,
         descriptor_writes: impl IntoIterator<Item = WriteDescriptorSet>,
@@ -113,58 +101,50 @@ where
     }
 }
 
-unsafe impl<P> DescriptorSet for PersistentDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+unsafe impl DescriptorSet for PersistentDescriptorSet {
+    #[inline]
     fn alloc(&self) -> &DescriptorPoolAlloc {
-        self.inner.alloc().inner()
+        &self.inner.alloc().inner
     }
 
+    #[inline]
     fn pool(&self) -> &DescriptorPool {
-        self.inner.alloc().pool()
+        &self.inner.alloc().pool
     }
 
+    #[inline]
     fn resources(&self) -> &DescriptorSetResources {
         &self.resources
     }
 }
 
-unsafe impl<P> VulkanObject for PersistentDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+unsafe impl VulkanObject for PersistentDescriptorSet {
     type Handle = ash::vk::DescriptorSet;
 
+    #[inline]
     fn handle(&self) -> Self::Handle {
         self.inner.handle()
     }
 }
 
-unsafe impl<P> DeviceOwned for PersistentDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+unsafe impl DeviceOwned for PersistentDescriptorSet {
+    #[inline]
     fn device(&self) -> &Arc<Device> {
         self.layout().device()
     }
 }
 
-impl<P> PartialEq for PersistentDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+impl PartialEq for PersistentDescriptorSet {
+    #[inline]
     fn eq(&self, other: &Self) -> bool {
         self.inner == other.inner
     }
 }
 
-impl<P> Eq for PersistentDescriptorSet<P> where P: DescriptorSetAlloc {}
+impl Eq for PersistentDescriptorSet {}
 
-impl<P> Hash for PersistentDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+impl Hash for PersistentDescriptorSet {
+    #[inline]
     fn hash<H: Hasher>(&self, state: &mut H) {
         self.inner.hash(state);
     }

vulkano/src/descriptor_set/sys.rs

@@ -1,7 +1,7 @@
 //! Low-level descriptor set.
 
 use super::{
-    allocator::{DescriptorSetAlloc, DescriptorSetAllocator, StandardDescriptorSetAlloc},
+    allocator::{DescriptorSetAlloc, DescriptorSetAllocator},
     pool::DescriptorPool,
     CopyDescriptorSet,
 };
@@ -14,60 +14,61 @@ use crate::{
     Validated, ValidationError, VulkanError, VulkanObject,
 };
 use smallvec::SmallVec;
-use std::{fmt::Debug, hash::Hash, sync::Arc};
+use std::{
+    fmt::Debug,
+    hash::{Hash, Hasher},
+    mem::ManuallyDrop,
+    sync::Arc,
+};
 
 /// Low-level descriptor set.
 ///
 /// This descriptor set does not keep track of synchronization,
 /// nor does it store any information on what resources have been written to each descriptor.
 #[derive(Debug)]
-pub struct UnsafeDescriptorSet<P = StandardDescriptorSetAlloc> {
-    alloc: P,
+pub struct UnsafeDescriptorSet {
+    allocation: ManuallyDrop<DescriptorSetAlloc>,
+    allocator: Arc<dyn DescriptorSetAllocator>,
 }
 
 impl UnsafeDescriptorSet {
     /// Allocates a new descriptor set and returns it.
     #[inline]
-    pub fn new<A>(
-        allocator: &A,
+    pub fn new(
+        allocator: Arc<dyn DescriptorSetAllocator>,
         layout: &Arc<DescriptorSetLayout>,
         variable_descriptor_count: u32,
-    ) -> Result<UnsafeDescriptorSet<A::Alloc>, Validated<VulkanError>>
-    where
-        A: DescriptorSetAllocator + ?Sized,
-    {
+    ) -> Result<UnsafeDescriptorSet, Validated<VulkanError>> {
+        let allocation = allocator.allocate(layout, variable_descriptor_count)?;
+
         Ok(UnsafeDescriptorSet {
-            alloc: allocator.allocate(layout, variable_descriptor_count)?,
+            allocation: ManuallyDrop::new(allocation),
+            allocator,
         })
     }
-}
 
-impl<P> UnsafeDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
     /// Returns the allocation of this descriptor set.
     #[inline]
-    pub fn alloc(&self) -> &P {
-        &self.alloc
+    pub fn alloc(&self) -> &DescriptorSetAlloc {
+        &self.allocation
     }
 
     /// Returns the descriptor pool that the descriptor set was allocated from.
     #[inline]
     pub fn pool(&self) -> &DescriptorPool {
-        self.alloc.pool()
+        &self.allocation.pool
     }
 
     /// Returns the layout of this descriptor set.
     #[inline]
     pub fn layout(&self) -> &Arc<DescriptorSetLayout> {
-        self.alloc.inner().layout()
+        self.allocation.inner.layout()
     }
 
     /// Returns the variable descriptor count that this descriptor set was allocated with.
     #[inline]
     pub fn variable_descriptor_count(&self) -> u32 {
-        self.alloc.inner().variable_descriptor_count()
+        self.allocation.inner.variable_descriptor_count()
     }
 
     /// Updates the descriptor set with new values.
@@ -205,46 +206,42 @@ where
     }
 }
 
-unsafe impl<P> VulkanObject for UnsafeDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+impl Drop for UnsafeDescriptorSet {
+    #[inline]
+    fn drop(&mut self) {
+        let allocation = unsafe { ManuallyDrop::take(&mut self.allocation) };
+        unsafe { self.allocator.deallocate(allocation) };
+    }
+}
+
+unsafe impl VulkanObject for UnsafeDescriptorSet {
     type Handle = ash::vk::DescriptorSet;
 
     #[inline]
     fn handle(&self) -> Self::Handle {
-        self.alloc.inner().handle()
+        self.allocation.inner.handle()
     }
 }
 
-unsafe impl<P> DeviceOwned for UnsafeDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+unsafe impl DeviceOwned for UnsafeDescriptorSet {
     #[inline]
     fn device(&self) -> &Arc<Device> {
-        self.alloc.inner().device()
+        self.allocation.inner.device()
     }
 }
 
-impl<P> PartialEq for UnsafeDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+impl PartialEq for UnsafeDescriptorSet {
     #[inline]
     fn eq(&self, other: &Self) -> bool {
-        self.alloc.inner() == other.alloc.inner()
+        self.allocation.inner == other.allocation.inner
     }
 }
 
-impl<P> Eq for UnsafeDescriptorSet<P> where P: DescriptorSetAlloc {}
+impl Eq for UnsafeDescriptorSet {}
 
-impl<P> Hash for UnsafeDescriptorSet<P>
-where
-    P: DescriptorSetAlloc,
-{
+impl Hash for UnsafeDescriptorSet {
     #[inline]
-    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-        self.alloc.inner().hash(state);
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.allocation.inner.hash(state);
     }
 }

vulkano/src/descriptor_set/update.rs

@@ -1,5 +1,4 @@
 use super::{
-    allocator::DescriptorSetAlloc,
     layout::{DescriptorSetLayout, DescriptorType},
     sys::UnsafeDescriptorSet,
     DescriptorSet,
@@ -1625,13 +1624,10 @@ impl CopyDescriptorSet {
         }
     }
 
-    pub(crate) fn validate<P>(
+    pub(crate) fn validate(
         &self,
-        dst_set: &UnsafeDescriptorSet<P>,
-    ) -> Result<(), Box<ValidationError>>
-    where
-        P: DescriptorSetAlloc,
-    {
+        dst_set: &UnsafeDescriptorSet,
+    ) -> Result<(), Box<ValidationError>> {
         let &Self {
             ref src_set,
             src_binding,

vulkano/src/image/sampler/ycbcr.rs

@@ -40,19 +40,25 @@
 //!
 //! # let device: std::sync::Arc<vulkano::device::Device> = return;
 //! # let memory_allocator: std::sync::Arc<vulkano::memory::allocator::StandardMemoryAllocator> = return;
-//! # let descriptor_set_allocator: vulkano::descriptor_set::allocator::StandardDescriptorSetAllocator = return;
+//! # let descriptor_set_allocator: std::sync::Arc<vulkano::descriptor_set::allocator::StandardDescriptorSetAllocator> = return;
 //! #
-//! let conversion = SamplerYcbcrConversion::new(device.clone(), SamplerYcbcrConversionCreateInfo {
+//! let conversion = SamplerYcbcrConversion::new(
+//!     device.clone(),
+//!     SamplerYcbcrConversionCreateInfo {
 //!         format: Format::G8_B8_R8_3PLANE_420_UNORM,
 //!         ycbcr_model: SamplerYcbcrModelConversion::YcbcrIdentity,
 //!         ..Default::default()
-//! })
+//!     },
+//! )
 //! .unwrap();
 //!
-//! let sampler = Sampler::new(device.clone(), SamplerCreateInfo {
+//! let sampler = Sampler::new(
+//!     device.clone(),
+//!     SamplerCreateInfo {
 //!         sampler_ycbcr_conversion: Some(conversion.clone()),
 //!         ..Default::default()
-//! })
+//!     },
+//! )
 //! .unwrap();
 //!
 //! let descriptor_set_layout = DescriptorSetLayout::new(
@@ -63,7 +69,9 @@
 //!             DescriptorSetLayoutBinding {
 //!                 stages: ShaderStage::Fragment.into(),
 //!                 immutable_samplers: vec![sampler],
-//!                 ..DescriptorSetLayoutBinding::descriptor_type(DescriptorType::CombinedImageSampler)
+//!                 ..DescriptorSetLayoutBinding::descriptor_type(
+//!                     DescriptorType::CombinedImageSampler
+//!                 )
 //!             },
 //!         )]
 //!         .into(),
@@ -92,7 +100,7 @@
 //! let image_view = ImageView::new(image, create_info).unwrap();
 //!
 //! let descriptor_set = PersistentDescriptorSet::new(
-//!     &descriptor_set_allocator,
+//!     descriptor_set_allocator.clone(),
 //!     descriptor_set_layout.clone(),
 //!     [WriteDescriptorSet::image_view(0, image_view)],
 //!     [],

vulkano/src/pipeline/compute.rs

@@ -540,9 +540,12 @@ mod tests {
         )
         .unwrap();
 
-        let ds_allocator = StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+        let ds_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+            device.clone(),
+            Default::default(),
+        ));
         let set = PersistentDescriptorSet::new(
-            &ds_allocator,
+            ds_allocator,
             pipeline.layout().set_layouts().get(0).unwrap().clone(),
             [WriteDescriptorSet::buffer(0, data_buffer.clone())],
             [],
@@ -681,9 +684,12 @@ mod tests {
         )
         .unwrap();
 
-        let ds_allocator = StandardDescriptorSetAllocator::new(device.clone(), Default::default());
+        let ds_allocator = Arc::new(StandardDescriptorSetAllocator::new(
+            device.clone(),
+            Default::default(),
+        ));
         let set = PersistentDescriptorSet::new(
-            &ds_allocator,
+            ds_allocator,
             pipeline.layout().set_layouts().get(0).unwrap().clone(),
             [WriteDescriptorSet::buffer(0, data_buffer.clone())],
             [],