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merged 3 commits into from
Nov 2, 2025
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examples: Prevent invalid semaphore reuse across frames #1009

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151047d
examples: Have a unique semaphore per swapchain image
MarijnS95 Oct 11, 2025
9dab58e
examples: Wait earlier for command-buffer fence to prevent semaphore …
MarijnS95 Oct 11, 2025
8452dff
examples: Implement triple-buffering
MarijnS95 Oct 11, 2025
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27 changes: 18 additions & 9 deletions ash-examples/src/bin/texture.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -352,8 +352,8 @@ fn main() -> Result<(), Box<dyn Error>> {

record_submit_commandbuffer(
&base.device,
base.setup_command_buffer,
base.setup_commands_reuse_fence,
base.app_setup_command_buffer,
vk::Fence::null(),
base.present_queue,
&[],
&[],
Expand Down Expand Up @@ -687,13 +687,19 @@ fn main() -> Result<(), Box<dyn Error>> {

let graphic_pipeline = graphics_pipelines[0];

let _ = base.render_loop(|| {
let _ = base.render_loop(|frame_index| {
let present_complete_semaphore =
base.present_complete_semaphores[frame_index % MAX_FRAME_LATENCY];
let draw_commands_reuse_fence =
base.draw_commands_reuse_fences[frame_index % MAX_FRAME_LATENCY];
let draw_command_buffer = base.draw_command_buffers[frame_index % MAX_FRAME_LATENCY];

let (present_index, _) = base
.swapchain_loader
.acquire_next_image(
base.swapchain,
u64::MAX,
base.present_complete_semaphore,
present_complete_semaphore,
vk::Fence::null(),
)
.unwrap();
Expand All @@ -711,6 +717,9 @@ fn main() -> Result<(), Box<dyn Error>> {
},
];

let rendering_complete_semaphore =
base.rendering_complete_semaphores[present_index as usize];

let render_pass_begin_info = vk::RenderPassBeginInfo::default()
.render_pass(renderpass)
.framebuffer(framebuffers[present_index as usize])
Expand All @@ -719,12 +728,12 @@ fn main() -> Result<(), Box<dyn Error>> {

record_submit_commandbuffer(
&base.device,
base.draw_command_buffer,
base.draw_commands_reuse_fence,
draw_command_buffer,
draw_commands_reuse_fence,
base.present_queue,
&[vk::PipelineStageFlags::BOTTOM_OF_PIPE],
&[base.present_complete_semaphore],
&[base.rendering_complete_semaphore],
&[present_complete_semaphore],
&[rendering_complete_semaphore],
|device, draw_command_buffer| {
device.cmd_begin_render_pass(
draw_command_buffer,
Expand Down Expand Up @@ -773,7 +782,7 @@ fn main() -> Result<(), Box<dyn Error>> {
);
let present_info = vk::PresentInfoKHR {
wait_semaphore_count: 1,
p_wait_semaphores: &base.rendering_complete_semaphore,
p_wait_semaphores: &rendering_complete_semaphore,
swapchain_count: 1,
p_swapchains: &base.swapchain,
p_image_indices: &present_index,
Expand Down
25 changes: 17 additions & 8 deletions ash-examples/src/bin/triangle.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -349,13 +349,19 @@ fn main() -> Result<(), Box<dyn Error>> {

let graphic_pipeline = graphics_pipelines[0];

let _ = base.render_loop(|| {
let _ = base.render_loop(|frame_index| {
let present_complete_semaphore =
base.present_complete_semaphores[frame_index % MAX_FRAME_LATENCY];
let draw_commands_reuse_fence =
base.draw_commands_reuse_fences[frame_index % MAX_FRAME_LATENCY];
let draw_command_buffer = base.draw_command_buffers[frame_index % MAX_FRAME_LATENCY];

let (present_index, _) = base
.swapchain_loader
.acquire_next_image(
base.swapchain,
u64::MAX,
base.present_complete_semaphore,
present_complete_semaphore,
vk::Fence::null(),
)
.unwrap();
Expand All @@ -373,6 +379,9 @@ fn main() -> Result<(), Box<dyn Error>> {
},
];

let rendering_complete_semaphore =
base.rendering_complete_semaphores[present_index as usize];

let render_pass_begin_info = vk::RenderPassBeginInfo::default()
.render_pass(renderpass)
.framebuffer(framebuffers[present_index as usize])
Expand All @@ -381,12 +390,12 @@ fn main() -> Result<(), Box<dyn Error>> {

record_submit_commandbuffer(
&base.device,
base.draw_command_buffer,
base.draw_commands_reuse_fence,
draw_command_buffer,
draw_commands_reuse_fence,
base.present_queue,
&[vk::PipelineStageFlags::COLOR_ATTACHMENT_OUTPUT],
&[base.present_complete_semaphore],
&[base.rendering_complete_semaphore],
&[present_complete_semaphore],
&[rendering_complete_semaphore],
|device, draw_command_buffer| {
device.cmd_begin_render_pass(
draw_command_buffer,
Expand Down Expand Up @@ -425,11 +434,11 @@ fn main() -> Result<(), Box<dyn Error>> {
device.cmd_end_render_pass(draw_command_buffer);
},
);
let wait_semaphors = [base.rendering_complete_semaphore];
let wait_semaphores = [rendering_complete_semaphore];
let swapchains = [base.swapchain];
let image_indices = [present_index];
let present_info = vk::PresentInfoKHR::default()
.wait_semaphores(&wait_semaphors) // &base.rendering_complete_semaphore)
.wait_semaphores(&wait_semaphores)
.swapchains(&swapchains)
.image_indices(&image_indices);

Expand Down
123 changes: 72 additions & 51 deletions ash-examples/src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,9 @@ use winit::{
window::WindowBuilder,
};

// The maximum number of frames we allow to be in flight at any given time
pub const MAX_FRAME_LATENCY: usize = 3;

// Simple offset_of macro akin to C++ offsetof
#[macro_export]
macro_rules! offset_of {
Expand All @@ -36,9 +39,7 @@ macro_rules! offset_of {
}
}};
}
/// Helper function for submitting command buffers. Immediately waits for the fence before the command buffer
/// is executed. That way we can delay the waiting for the fences by 1 frame which is good for performance.
/// Make sure to create the fence in a signaled state on the first use.

#[allow(clippy::too_many_arguments)]
pub fn record_submit_commandbuffer<F: FnOnce(&Device, vk::CommandBuffer)>(
device: &Device,
Expand All @@ -51,14 +52,6 @@ pub fn record_submit_commandbuffer<F: FnOnce(&Device, vk::CommandBuffer)>(
f: F,
) {
unsafe {
device
.wait_for_fences(&[command_buffer_reuse_fence], true, u64::MAX)
.expect("Wait for fence failed.");

device
.reset_fences(&[command_buffer_reuse_fence])
.expect("Reset fences failed.");

device
.reset_command_buffer(
command_buffer,
Expand Down Expand Up @@ -143,6 +136,7 @@ pub struct ExampleBase {
pub debug_utils_loader: debug_utils::Instance,
pub window: winit::window::Window,
pub event_loop: RefCell<EventLoop<()>>,
pub frame_index: RefCell<usize>,
pub debug_call_back: vk::DebugUtilsMessengerEXT,

pub pdevice: vk::PhysicalDevice,
Expand All @@ -159,22 +153,22 @@ pub struct ExampleBase {
pub present_image_views: Vec<vk::ImageView>,

pub pool: vk::CommandPool,
pub draw_command_buffer: vk::CommandBuffer,
pub draw_command_buffers: [vk::CommandBuffer; MAX_FRAME_LATENCY],
pub setup_command_buffer: vk::CommandBuffer,
pub app_setup_command_buffer: vk::CommandBuffer,

pub depth_image: vk::Image,
pub depth_image_view: vk::ImageView,
pub depth_image_memory: vk::DeviceMemory,

pub present_complete_semaphore: vk::Semaphore,
pub rendering_complete_semaphore: vk::Semaphore,
pub present_complete_semaphores: [vk::Semaphore; MAX_FRAME_LATENCY],
pub rendering_complete_semaphores: Vec<vk::Semaphore>,

pub draw_commands_reuse_fence: vk::Fence,
pub setup_commands_reuse_fence: vk::Fence,
pub draw_commands_reuse_fences: [vk::Fence; MAX_FRAME_LATENCY],
}

impl ExampleBase {
pub fn render_loop<F: Fn()>(&self, f: F) -> Result<(), impl Error> {
pub fn render_loop<F: Fn(usize)>(&self, f: F) -> Result<(), impl Error> {
self.event_loop.borrow_mut().run_on_demand(|event, elwp| {
elwp.set_control_flow(ControlFlow::Poll);
match event {
Expand All @@ -194,7 +188,24 @@ impl ExampleBase {
} => {
elwp.exit();
}
Event::AboutToWait => f(),
Event::AboutToWait => {
let mut frame_index = self.frame_index.borrow_mut();

// The fence from 3 frames ago, that will also be signaled this frame
let draw_commands_reuse_fence =
self.draw_commands_reuse_fences[*frame_index % MAX_FRAME_LATENCY];
unsafe {
self.device
.wait_for_fences(&[draw_commands_reuse_fence], true, u64::MAX)
}
.expect("Wait for fence failed.");

unsafe { self.device.reset_fences(&[draw_commands_reuse_fence]) }
.expect("Reset fences failed.");

f(*frame_index);
*frame_index += 1;
}
_ => (),
}
})
Expand Down Expand Up @@ -400,15 +411,18 @@ impl ExampleBase {
let pool = device.create_command_pool(&pool_create_info, None).unwrap();

let command_buffer_allocate_info = vk::CommandBufferAllocateInfo::default()
.command_buffer_count(2)
.command_buffer_count(2 + MAX_FRAME_LATENCY as u32)
.command_pool(pool)
.level(vk::CommandBufferLevel::PRIMARY);

let command_buffers = device
.allocate_command_buffers(&command_buffer_allocate_info)
.unwrap();
let setup_command_buffer = command_buffers[0];
let draw_command_buffer = command_buffers[1];
let app_setup_command_buffer = command_buffers[1];
let draw_command_buffers = command_buffers[2..][..MAX_FRAME_LATENCY]
.try_into()
.unwrap();

let present_images = swapchain_loader.get_swapchain_images(swapchain).unwrap();
let present_image_views: Vec<vk::ImageView> = present_images
Expand Down Expand Up @@ -467,20 +481,10 @@ impl ExampleBase {
.bind_image_memory(depth_image, depth_image_memory, 0)
.expect("Unable to bind depth image memory");

let fence_create_info =
vk::FenceCreateInfo::default().flags(vk::FenceCreateFlags::SIGNALED);

let draw_commands_reuse_fence = device
.create_fence(&fence_create_info, None)
.expect("Create fence failed.");
let setup_commands_reuse_fence = device
.create_fence(&fence_create_info, None)
.expect("Create fence failed.");

record_submit_commandbuffer(
&device,
setup_command_buffer,
setup_commands_reuse_fence,
vk::Fence::null(),
present_queue,
&[],
&[],
Expand Down Expand Up @@ -530,15 +534,31 @@ impl ExampleBase {

let semaphore_create_info = vk::SemaphoreCreateInfo::default();

let present_complete_semaphore = device
.create_semaphore(&semaphore_create_info, None)
.unwrap();
let rendering_complete_semaphore = device
.create_semaphore(&semaphore_create_info, None)
.unwrap();
let present_complete_semaphores = std::array::from_fn(|_| {
device
.create_semaphore(&semaphore_create_info, None)
.unwrap()
});
let rendering_complete_semaphores = (0..present_images.len())
.map(|_| {
device
.create_semaphore(&semaphore_create_info, None)
.unwrap()
})
.collect();

let fence_create_info =
vk::FenceCreateInfo::default().flags(vk::FenceCreateFlags::SIGNALED);

let draw_commands_reuse_fences = std::array::from_fn(|_| {
device
.create_fence(&fence_create_info, None)
.expect("Create fence failed.")
});

Ok(Self {
event_loop: RefCell::new(event_loop),
frame_index: RefCell::new(0),
entry,
instance,
device,
Expand All @@ -555,14 +575,14 @@ impl ExampleBase {
present_images,
present_image_views,
pool,
draw_command_buffer,
draw_command_buffers,
setup_command_buffer,
app_setup_command_buffer,
depth_image,
depth_image_view,
present_complete_semaphore,
rendering_complete_semaphore,
draw_commands_reuse_fence,
setup_commands_reuse_fence,
present_complete_semaphores,
rendering_complete_semaphores,
draw_commands_reuse_fences,
surface,
debug_call_back,
debug_utils_loader,
Expand All @@ -576,18 +596,19 @@ impl Drop for ExampleBase {
fn drop(&mut self) {
unsafe {
self.device.device_wait_idle().unwrap();
self.device
.destroy_semaphore(self.present_complete_semaphore, None);
self.device
.destroy_semaphore(self.rendering_complete_semaphore, None);
self.device
.destroy_fence(self.draw_commands_reuse_fence, None);
self.device
.destroy_fence(self.setup_commands_reuse_fence, None);
for &semaphore in &self.present_complete_semaphores {
self.device.destroy_semaphore(semaphore, None);
}
for &semaphore in &self.rendering_complete_semaphores {
self.device.destroy_semaphore(semaphore, None);
}
for &fence in &self.draw_commands_reuse_fences {
self.device.destroy_fence(fence, None);
}
self.device.free_memory(self.depth_image_memory, None);
self.device.destroy_image_view(self.depth_image_view, None);
self.device.destroy_image(self.depth_image, None);
for &image_view in self.present_image_views.iter() {
for &image_view in &self.present_image_views {
self.device.destroy_image_view(image_view, None);
}
self.device.destroy_command_pool(self.pool, None);
Expand Down