Re: [FFmpeg-devel] [PATCH 1/2] vulkan: synchronize access to execution pool fences

[Lynne <dev@lynne.ee>]

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Jun 7, 2023, 01:45 by dev@lynne.ee:

> Jun 7, 2023, 01:22 by dev@lynne.ee:
>
>> vkResetFences is specified as being user-synchronized
>> (yet vkWaitFences, is not).
>>
>> Patch attached.
>>
>
> Stray change in vulkan_decode.c removed locally.
>

Also removed the vkWaitForFences call during
the _start function from the mutex lock, as
it's safe to do so, and added a comment.


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From ef13ab7974ea3833e1063dfd14e92550ad27b53b Mon Sep 17 00:00:00 2001
From: Lynne <dev@lynne.ee>
Date: Wed, 7 Jun 2023 00:24:43 +0200
Subject: [PATCH v2 1/2] vulkan: synchronize access to execution pool fences

vkResetFences is specified as being user-synchronized
(yet vkWaitFences, is not).
---
 libavutil/vulkan.c | 16 +++++++++++++---
 libavutil/vulkan.h |  2 ++
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/libavutil/vulkan.c b/libavutil/vulkan.c
index bc4466e6c9..b1c585292e 100644
--- a/libavutil/vulkan.c
+++ b/libavutil/vulkan.c
@@ -241,6 +241,7 @@ void ff_vk_exec_pool_free(FFVulkanContext *s, FFVkExecPool *pool)
             vk->WaitForFences(s->hwctx->act_dev, 1, &e->fence, VK_TRUE, UINT64_MAX);
             vk->DestroyFence(s->hwctx->act_dev, e->fence, s->hwctx->alloc);
         }
+        pthread_mutex_destroy(&e->lock);
 
         ff_vk_exec_discard_deps(s, e);
 
@@ -379,12 +380,17 @@ int ff_vk_exec_pool_init(FFVulkanContext *s, FFVkQueueFamilyCtx *qf,
     /* Init contexts */
     for (int i = 0; i < pool->pool_size; i++) {
         FFVkExecContext *e = &pool->contexts[i];
-
-        /* Fence */
         VkFenceCreateInfo fence_create = {
             .sType = VK_STRUCTURE_TYPE_FENCE_CREATE_INFO,
             .flags = VK_FENCE_CREATE_SIGNALED_BIT,
         };
+
+        /* Mutex */
+        err = pthread_mutex_init(&e->lock, NULL);
+        if (err != 0)
+            return AVERROR(err);
+
+        /* Fence */
         ret = vk->CreateFence(s->hwctx->act_dev, &fence_create, s->hwctx->alloc,
                               &e->fence);
         if (ret != VK_SUCCESS) {
@@ -488,9 +494,13 @@ int ff_vk_exec_start(FFVulkanContext *s, FFVkExecContext *e)
         .flags = VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT,
     };
 
-    /* Create the fence and don't wait for it initially */
+    /* Wait for the fence to be signalled */
     vk->WaitForFences(s->hwctx->act_dev, 1, &e->fence, VK_TRUE, UINT64_MAX);
+
+    /* vkResetFences is defined as being host-synchronized */
+    pthread_mutex_lock(&e->lock);
     vk->ResetFences(s->hwctx->act_dev, 1, &e->fence);
+    pthread_mutex_unlock(&e->lock);
 
     /* Discard queue dependencies */
     ff_vk_exec_discard_deps(s, e);
diff --git a/libavutil/vulkan.h b/libavutil/vulkan.h
index 58da720a1c..bbbc9374ae 100644
--- a/libavutil/vulkan.h
+++ b/libavutil/vulkan.h
@@ -23,6 +23,7 @@
 
 #include <stdatomic.h>
 
+#include "thread.h"
 #include "pixdesc.h"
 #include "bprint.h"
 #include "hwcontext.h"
@@ -152,6 +153,7 @@ typedef struct FFVulkanPipeline {
 typedef struct FFVkExecContext {
     int idx;
     const struct FFVkExecPool *parent;
+    pthread_mutex_t lock;
 
     /* Queue for the execution context */
     VkQueue queue;
-- 
2.40.1


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