From 58b0ae84b56996304b6ad373e4f6cff2cf6bdd41 Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Thu, 10 Sep 2020 03:43:30 -0300
Subject: renderer_vulkan: Make unconditional use of VK_KHR_timeline_semaphore

This reworks how host<->device synchronization works on the Vulkan
backend. Instead of "protecting" resources with a fence and signalling
these as free when the fence is known to be signalled by the host GPU,
use timeline semaphores.

Vulkan timeline semaphores allow use to work on a subset of D3D12
fences. As far as we are concerned, timeline semaphores are a value set
by the host or the device that can be waited by either of them.

Taking advantange of this, we can have a monolithically increasing
atomic value for each submission to the graphics queue. Instead of
protecting resources with a fence, we simply store the current logical
tick (the atomic value stored in CPU memory). When we want to know if a
resource is free, it can be compared to the current GPU tick.

This greatly simplifies resource management code and the free status of
resources should have less false negatives.

To workaround bugs in validation layers, when these are attached there's
a thread waiting for timeline semaphores.
---
 src/video_core/renderer_vulkan/vk_descriptor_pool.h | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'src/video_core/renderer_vulkan/vk_descriptor_pool.h')

diff --git a/src/video_core/renderer_vulkan/vk_descriptor_pool.h b/src/video_core/renderer_vulkan/vk_descriptor_pool.h
index 9efa66bef..544f32a20 100644
--- a/src/video_core/renderer_vulkan/vk_descriptor_pool.h
+++ b/src/video_core/renderer_vulkan/vk_descriptor_pool.h
@@ -6,21 +6,24 @@
 
 #include <vector>
 
-#include "video_core/renderer_vulkan/vk_resource_manager.h"
+#include "video_core/renderer_vulkan/vk_resource_pool.h"
 #include "video_core/renderer_vulkan/wrapper.h"
 
 namespace Vulkan {
 
+class VKDevice;
 class VKDescriptorPool;
+class VKScheduler;
 
-class DescriptorAllocator final : public VKFencedPool {
+class DescriptorAllocator final : public ResourcePool {
 public:
     explicit DescriptorAllocator(VKDescriptorPool& descriptor_pool, VkDescriptorSetLayout layout);
     ~DescriptorAllocator() override;
 
+    DescriptorAllocator& operator=(const DescriptorAllocator&) = delete;
     DescriptorAllocator(const DescriptorAllocator&) = delete;
 
-    VkDescriptorSet Commit(VKFence& fence);
+    VkDescriptorSet Commit();
 
 protected:
     void Allocate(std::size_t begin, std::size_t end) override;
@@ -36,15 +39,19 @@ class VKDescriptorPool final {
     friend DescriptorAllocator;
 
 public:
-    explicit VKDescriptorPool(const VKDevice& device);
+    explicit VKDescriptorPool(const VKDevice& device, VKScheduler& scheduler);
     ~VKDescriptorPool();
 
+    VKDescriptorPool(const VKDescriptorPool&) = delete;
+    VKDescriptorPool& operator=(const VKDescriptorPool&) = delete;
+
 private:
     vk::DescriptorPool* AllocateNewPool();
 
     vk::DescriptorSets AllocateDescriptors(VkDescriptorSetLayout layout, std::size_t count);
 
     const VKDevice& device;
+    MasterSemaphore& master_semaphore;
 
     std::vector<vk::DescriptorPool> pools;
     vk::DescriptorPool* active_pool;
-- 
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