framebuffer: Fix timeline semaphore leak and corruption on resize

During sequence reconfiguration (e.g., resolution change), the
NvPerFrameDecodeImageSet::init() function was unconditionally creating
new timeline semaphores without checking if they already existed.

This caused two problems:
1. Memory leak: Old semaphores were never destroyed (the 8 allocations
   / 1456 bytes leak seen in debug builds)
2. Synchronization corruption: In-flight GPU work was still waiting on
   the OLD semaphore values, but the NEW semaphores started at
   initialValue=0. This caused device lost when using display
   presentation, because the swap chain consumer was using the
   corrupted timeline synchronization.

Headless mode (--noPresent) was unaffected because timeline semaphores
are not used for presentation synchronization in that path.

Fix: Only create the timeline semaphores if they don't already exist.
On reconfigure, reuse the existing semaphores to preserve in-flight
synchronization state.

Signed-off-by: Tony Zlatinski <tzlatinski@nvidia.com>

Author: zlatinski

vk_video_decoder/libs/VulkanVideoFrameBuffer/VulkanVideoFrameBuffer.cpp

@@ -944,19 +944,23 @@ int32_t NvPerFrameDecodeImageSet::init(const VulkanDeviceContext* vkDevCtx,
         }
     }
 
-    // Create timeline semaphores instead of binary semaphores
-    VkSemaphoreTypeCreateInfo timelineCreateInfo = {};
-    timelineCreateInfo.sType = VK_STRUCTURE_TYPE_SEMAPHORE_TYPE_CREATE_INFO;
-    timelineCreateInfo.pNext = nullptr;
-    timelineCreateInfo.semaphoreType = VK_SEMAPHORE_TYPE_TIMELINE;
-    timelineCreateInfo.initialValue = 0ULL;
-
-    VkSemaphoreCreateInfo semInfo = { VK_STRUCTURE_TYPE_SEMAPHORE_CREATE_INFO, &timelineCreateInfo };
-    VkResult result = vkDevCtx->CreateSemaphore(*vkDevCtx, &semInfo, nullptr, &m_frameCompleteSemaphore);
-    assert(result == VK_SUCCESS);
+    // Create timeline semaphores instead of binary semaphores.
+    // Only create if not already created - on reconfigure, we MUST reuse the existing
+    // semaphores to avoid corrupting in-flight synchronization.
+    if (m_frameCompleteSemaphore == VK_NULL_HANDLE) {
+        VkSemaphoreTypeCreateInfo timelineCreateInfo = {};
+        timelineCreateInfo.sType = VK_STRUCTURE_TYPE_SEMAPHORE_TYPE_CREATE_INFO;
+        timelineCreateInfo.pNext = nullptr;
+        timelineCreateInfo.semaphoreType = VK_SEMAPHORE_TYPE_TIMELINE;
+        timelineCreateInfo.initialValue = 0ULL;
+
+        VkSemaphoreCreateInfo semInfo = { VK_STRUCTURE_TYPE_SEMAPHORE_CREATE_INFO, &timelineCreateInfo };
+        VkResult result = vkDevCtx->CreateSemaphore(*vkDevCtx, &semInfo, nullptr, &m_frameCompleteSemaphore);
+        assert(result == VK_SUCCESS);
 
-    result = vkDevCtx->CreateSemaphore(*vkDevCtx, &semInfo, nullptr, &m_consumerCompleteSemaphore);
-    assert(result == VK_SUCCESS);
+        result = vkDevCtx->CreateSemaphore(*vkDevCtx, &semInfo, nullptr, &m_consumerCompleteSemaphore);
+        assert(result == VK_SUCCESS);
+    }
 
     m_videoProfile.InitFromProfile(pDecodeProfile);