Synchronise access to the ring buffer pool

We need to synchronise access to the ring buffer pool in order to avoid
concurrency bugs as multiple threads can mutate the state of the ring
buffer and if we do not serialise these changes then they can result in
errors.

Change-Id: If96e1707716370bcf57416cd505d16aa75c0d68c
Signed-off-by: Dennis Tsiang <dennis.tsiang@arm.com>

diff --git a/wsi/swapchain_base.cpp b/wsi/swapchain_base.cpp
index fb38a24..7f93c14 100644 (file)
--- a/wsi/swapchain_base.cpp
+++ b/wsi/swapchain_base.cpp
@@ -71,8 +71,10 @@ void swapchain_base::page_flip_thread()
 
       /* We want to present the oldest queued for present image from our present queue,
        * which we can find at the sc->pending_buffer_pool.head index. */
+      std::unique_lock<std::recursive_mutex> image_status_lock(m_image_status_mutex);
       auto pending_index = m_pending_buffer_pool.pop_front();
       assert(pending_index.has_value());
+      image_status_lock.unlock();
 
       /* We may need to wait for the payload of the present sync of the oldest pending image to be finished. */
       vk_res = image_wait_present(sc_images[*pending_index], timeout);
@@ -466,7 +468,9 @@ VkResult swapchain_base::queue_present(VkQueue queue, const VkPresentInfoKHR *pr
    }
 
    m_swapchain_images[image_index].status = swapchain_image::PENDING;
-   m_pending_buffer_pool.push_back(image_index);
+   bool buffer_pool_res = m_pending_buffer_pool.push_back(image_index);
+   (void)buffer_pool_res;
+   assert(buffer_pool_res);
    m_page_flip_semaphore.post();
    return VK_SUCCESS;
 }