vulkan: synchronize access to execution pool fences

vkResetFences is specified as being user-synchronized
(yet vkWaitFences, is not).

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);

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;