Vulkan sync

sync.md

Ordering

/* 1 */ vkCmdDispatch(cb, 1, 1, 1);
/* 2 */ vkCmdDispatch(cb, 1, 1, 1);

dispatches 1 and 2 aren't ordered wrt each other. So the threads spawned by 1 and 2 may start in any order, execute in parallel, and complete in any order.

/* 1 */ vkCmdDispatch(cb, 1, 1, 1);
        vkCmdPipelineBarrier2(cb,
                              srcStageMask = VK_PIPELINE_STAGE_2_ALL_COMMANDS_BIT,
                              srcAccessMask = VK_ACCESS_2_MEMORY_WRITE_BIT,
                              dstStageMask = VK_PIPELINE_STAGE_2_ALL_COMMANDS_BIT,
                              dstAccessMask = VK_ACCESS_2_MEMORY_READ_BIT | VK_ACCESS_2_MEMORY_WRITE_BIT);
/* 2 */ vkCmdDispatch(cb, 1, 1, 1);

now, the thread spawned by dispatch 1 will start, execute and complete before the thread spawned by dispatch 2 will start, execute and complete.