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// Copyright (c) 2016 The vulkano developers
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or https://opensource.org/licenses/MIT>,
// at your option. All files in the project carrying such
// notice may not be copied, modified, or distributed except
// according to those terms.
//! Represents an event that will happen on the GPU in the future.
//!
//! Whenever you ask the GPU to start an operation by using a function of the vulkano library (for
//! example executing a command buffer), this function will return a *future*. A future is an
//! object that implements [the `GpuFuture` trait](crate::sync::GpuFuture) and that represents the
//! point in time when this operation is over.
//!
//! No function in vulkano immediately sends an operation to the GPU (with the exception of some
//! unsafe low-level functions). Instead they return a future that is in the pending state. Before
//! the GPU actually starts doing anything, you have to *flush* the future by calling the `flush()`
//! method or one of its derivatives.
//!
//! Futures serve several roles:
//!
//! - Futures can be used to build dependencies between operations and makes it possible to ask
//! that an operation starts only after a previous operation is finished.
//! - Submitting an operation to the GPU is a costly operation. By chaining multiple operations
//! with futures you will submit them all at once instead of one by one, thereby reducing this
//! cost.
//! - Futures keep alive the resources and objects used by the GPU so that they don't get destroyed
//! while they are still in use.
//!
//! The last point means that you should keep futures alive in your program for as long as their
//! corresponding operation is potentially still being executed by the GPU. Dropping a future
//! earlier will block the current thread (after flushing, if necessary) until the GPU has finished
//! the operation, which is usually not what you want.
//!
//! If you write a function that submits an operation to the GPU in your program, you are
//! encouraged to let this function return the corresponding future and let the caller handle it.
//! This way the caller will be able to chain multiple futures together and decide when it wants to
//! keep the future alive or drop it.
//!
//! # Executing an operation after a future
//!
//! Respecting the order of operations on the GPU is important, as it is what *proves* vulkano that
//! what you are doing is indeed safe. For example if you submit two operations that modify the
//! same buffer, then you need to execute one after the other instead of submitting them
//! independently. Failing to do so would mean that these two operations could potentially execute
//! simultaneously on the GPU, which would be unsafe.
//!
//! This is done by calling one of the methods of the `GpuFuture` trait. For example calling
//! `prev_future.then_execute(command_buffer)` takes ownership of `prev_future` and will make sure
//! to only start executing `command_buffer` after the moment corresponding to `prev_future`
//! happens. The object returned by the `then_execute` function is itself a future that corresponds
//! to the moment when the execution of `command_buffer` ends.
//!
//! ## Between two different GPU queues
//!
//! When you want to perform an operation after another operation on two different queues, you
//! **must** put a *semaphore* between them. Failure to do so would result in a runtime error.
//! Adding a semaphore is a simple as replacing `prev_future.then_execute(...)` with
//! `prev_future.then_signal_semaphore().then_execute(...)`.
//!
//! > **Note**: A common use-case is using a transfer queue (ie. a queue that is only capable of
//! > performing transfer operations) to write data to a buffer, then read that data from the
//! > rendering queue.
//!
//! What happens when you do so is that the first queue will execute the first set of operations
//! (represented by `prev_future` in the example), then put a semaphore in the signalled state.
//! Meanwhile the second queue blocks (if necessary) until that same semaphore gets signalled, and
//! then only will execute the second set of operations.
//!
//! Since you want to avoid blocking the second queue as much as possible, you probably want to
//! flush the operation to the first queue as soon as possible. This can easily be done by calling
//! `then_signal_semaphore_and_flush()` instead of `then_signal_semaphore()`.
//!
//! ## Between several different GPU queues
//!
//! The `then_signal_semaphore()` method is appropriate when you perform an operation in one queue,
//! and want to see the result in another queue. However in some situations you want to start
//! multiple operations on several different queues.
//!
//! TODO: this is not yet implemented
//!
//! # Fences
//!
//! A `Fence` is an object that is used to signal the CPU when an operation on the GPU is finished.
//!
//! Signalling a fence is done by calling `then_signal_fence()` on a future. Just like semaphores,
//! you are encouraged to use `then_signal_fence_and_flush()` instead.
//!
//! Signalling a fence is kind of a "terminator" to a chain of futures
pub use self::{
fence_signal::{FenceSignalFuture, FenceSignalFutureBehavior},
join::JoinFuture,
now::{now, NowFuture},
semaphore_signal::SemaphoreSignalFuture,
};
use super::{fence::Fence, semaphore::Semaphore};
use crate::{
buffer::Buffer,
command_buffer::{
CommandBufferExecError, CommandBufferExecFuture, PrimaryCommandBufferAbstract, SubmitInfo,
},
device::{DeviceOwned, Queue},
image::{Image, ImageLayout},
memory::BindSparseInfo,
swapchain::{self, PresentFuture, PresentInfo, Swapchain, SwapchainPresentInfo},
DeviceSize, Validated, VulkanError,
};
use smallvec::SmallVec;
use std::{
error::Error,
fmt::{Display, Error as FmtError, Formatter},
ops::Range,
sync::Arc,
};
mod fence_signal;
mod join;
mod now;
mod semaphore_signal;
/// Represents an event that will happen on the GPU in the future.
///
/// See the documentation of the `sync` module for explanations about futures.
// TODO: consider switching all methods to take `&mut self` for optimization purposes
pub unsafe trait GpuFuture: DeviceOwned {
/// If possible, checks whether the submission has finished. If so, gives up ownership of the
/// resources used by these submissions.
///
/// It is highly recommended to call `cleanup_finished` from time to time. Doing so will
/// prevent memory usage from increasing over time, and will also destroy the locks on
/// resources used by the GPU.
fn cleanup_finished(&mut self);
/// Builds a submission that, if submitted, makes sure that the event represented by this
/// `GpuFuture` will happen, and possibly contains extra elements (eg. a semaphore wait or an
/// event wait) that makes the dependency with subsequent operations work.
///
/// It is the responsibility of the caller to ensure that the submission is going to be
/// submitted only once. However keep in mind that this function can perfectly be called
/// multiple times (as long as the returned object is only submitted once).
/// Also note that calling `flush()` on the future may change the value returned by
/// `build_submission()`.
///
/// It is however the responsibility of the implementation to not return the same submission
/// from multiple different future objects. For example if you implement `GpuFuture` on
/// `Arc<Foo>` then `build_submission()` must always return `SubmitAnyBuilder::Empty`,
/// otherwise it would be possible for the user to clone the `Arc` and make the same
/// submission be submitted multiple times.
///
/// It is also the responsibility of the implementation to ensure that it works if you call
/// `build_submission()` and submits the returned value without calling `flush()` first. In
/// other words, `build_submission()` should perform an implicit flush if necessary.
///
/// Once the caller has submitted the submission and has determined that the GPU has finished
/// executing it, it should call `signal_finished`. Failure to do so will incur a large runtime
/// overhead, as the future will have to block to make sure that it is finished.
unsafe fn build_submission(&self) -> Result<SubmitAnyBuilder, Validated<VulkanError>>;
/// Flushes the future and submits to the GPU the actions that will permit this future to
/// occur.
///
/// The implementation must remember that it was flushed. If the function is called multiple
/// times, only the first time must result in a flush.
fn flush(&self) -> Result<(), Validated<VulkanError>>;
/// Sets the future to its "complete" state, meaning that it can safely be destroyed.
///
/// This must only be done if you called `build_submission()`, submitted the returned
/// submission, and determined that it was finished.
///
/// The implementation must be aware that this function can be called multiple times on the
/// same future.
unsafe fn signal_finished(&self);
/// Returns the queue that triggers the event. Returns `None` if unknown or irrelevant.
///
/// If this function returns `None` and `queue_change_allowed` returns `false`, then a panic
/// is likely to occur if you use this future. This is only a problem if you implement
/// the `GpuFuture` trait yourself for a type outside of vulkano.
fn queue(&self) -> Option<Arc<Queue>>;
/// Returns `true` if elements submitted after this future can be submitted to a different
/// queue than the other returned by `queue()`.
fn queue_change_allowed(&self) -> bool;
/// Checks whether submitting something after this future grants access (exclusive or shared,
/// depending on the parameter) to the given buffer on the given queue.
///
/// > **Note**: Returning `Ok` means "access granted", while returning `Err` means
/// > "don't know". Therefore returning `Err` is never unsafe.
fn check_buffer_access(
&self,
buffer: &Buffer,
range: Range<DeviceSize>,
exclusive: bool,
queue: &Queue,
) -> Result<(), AccessCheckError>;
/// Checks whether submitting something after this future grants access (exclusive or shared,
/// depending on the parameter) to the given image on the given queue.
///
/// Implementations must ensure that the image is in the given layout. However if the `layout`
/// is `Undefined` then the implementation should accept any actual layout.
///
/// > **Note**: Returning `Ok` means "access granted", while returning `Err` means
/// > "don't know". Therefore returning `Err` is never unsafe.
///
/// > **Note**: Keep in mind that changing the layout of an image also requires exclusive
/// > access.
fn check_image_access(
&self,
image: &Image,
range: Range<DeviceSize>,
exclusive: bool,
expected_layout: ImageLayout,
queue: &Queue,
) -> Result<(), AccessCheckError>;
/// Checks whether accessing a swapchain image is permitted.
///
/// > **Note**: Setting `before` to `true` should skip checking the current future and always
/// > forward the call to the future before.
fn check_swapchain_image_acquired(
&self,
swapchain: &Swapchain,
image_index: u32,
before: bool,
) -> Result<(), AccessCheckError>;
/// Joins this future with another one, representing the moment when both events have happened.
// TODO: handle errors
fn join<F>(self, other: F) -> JoinFuture<Self, F>
where
Self: Sized,
F: GpuFuture,
{
join::join(self, other)
}
/// Executes a command buffer after this future.
///
/// > **Note**: This is just a shortcut function. The actual implementation is in the
/// > `CommandBuffer` trait.
fn then_execute(
self,
queue: Arc<Queue>,
command_buffer: Arc<impl PrimaryCommandBufferAbstract + 'static>,
) -> Result<CommandBufferExecFuture<Self>, CommandBufferExecError>
where
Self: Sized,
{
command_buffer.execute_after(self, queue)
}
/// Executes a command buffer after this future, on the same queue as the future.
///
/// > **Note**: This is just a shortcut function. The actual implementation is in the
/// > `CommandBuffer` trait.
fn then_execute_same_queue(
self,
command_buffer: Arc<impl PrimaryCommandBufferAbstract + 'static>,
) -> Result<CommandBufferExecFuture<Self>, CommandBufferExecError>
where
Self: Sized,
{
let queue = self.queue().unwrap();
command_buffer.execute_after(self, queue)
}
/// Signals a semaphore after this future. Returns another future that represents the signal.
///
/// Call this function when you want to execute some operations on a queue and want to see the
/// result on another queue.
#[inline]
fn then_signal_semaphore(self) -> SemaphoreSignalFuture<Self>
where
Self: Sized,
{
semaphore_signal::then_signal_semaphore(self)
}
/// Signals a semaphore after this future and flushes it. Returns another future that
/// represents the moment when the semaphore is signalled.
///
/// This is a just a shortcut for `then_signal_semaphore()` followed with `flush()`.
///
/// When you want to execute some operations A on a queue and some operations B on another
/// queue that need to see the results of A, it can be a good idea to submit A as soon as
/// possible while you're preparing B.
///
/// If you ran A and B on the same queue, you would have to decide between submitting A then
/// B, or A and B simultaneously. Both approaches have their trade-offs. But if A and B are
/// on two different queues, then you would need two submits anyway and it is always
/// advantageous to submit A as soon as possible.
#[inline]
fn then_signal_semaphore_and_flush(
self,
) -> Result<SemaphoreSignalFuture<Self>, Validated<VulkanError>>
where
Self: Sized,
{
let f = self.then_signal_semaphore();
f.flush()?;
Ok(f)
}
/// Signals a fence after this future. Returns another future that represents the signal.
///
/// > **Note**: More often than not you want to immediately flush the future after calling this
/// > function. If so, consider using `then_signal_fence_and_flush`.
#[inline]
fn then_signal_fence(self) -> FenceSignalFuture<Self>
where
Self: Sized,
{
fence_signal::then_signal_fence(self, FenceSignalFutureBehavior::Continue)
}
/// Signals a fence after this future. Returns another future that represents the signal.
///
/// This is a just a shortcut for `then_signal_fence()` followed with `flush()`.
#[inline]
fn then_signal_fence_and_flush(self) -> Result<FenceSignalFuture<Self>, Validated<VulkanError>>
where
Self: Sized,
{
let f = self.then_signal_fence();
f.flush()?;
Ok(f)
}
/// Presents a swapchain image after this future.
///
/// You should only ever do this indirectly after a `SwapchainAcquireFuture` of the same image,
/// otherwise an error will occur when flushing.
///
/// > **Note**: This is just a shortcut for the `Swapchain::present()` function.
#[inline]
fn then_swapchain_present(
self,
queue: Arc<Queue>,
swapchain_info: SwapchainPresentInfo,
) -> PresentFuture<Self>
where
Self: Sized,
{
swapchain::present(self, queue, swapchain_info)
}
/// Turn the current future into a `Box<dyn GpuFuture>`.
///
/// This is a helper function that calls `Box::new(yourFuture) as Box<dyn GpuFuture>`.
#[inline]
fn boxed(self) -> Box<dyn GpuFuture>
where
Self: Sized + 'static,
{
Box::new(self) as _
}
/// Turn the current future into a `Box<dyn GpuFuture + Send>`.
///
/// This is a helper function that calls `Box::new(yourFuture) as Box<dyn GpuFuture + Send>`.
#[inline]
fn boxed_send(self) -> Box<dyn GpuFuture + Send>
where
Self: Sized + Send + 'static,
{
Box::new(self) as _
}
/// Turn the current future into a `Box<dyn GpuFuture + Sync>`.
///
/// This is a helper function that calls `Box::new(yourFuture) as Box<dyn GpuFuture + Sync>`.
#[inline]
fn boxed_sync(self) -> Box<dyn GpuFuture + Sync>
where
Self: Sized + Sync + 'static,
{
Box::new(self) as _
}
/// Turn the current future into a `Box<dyn GpuFuture + Send + Sync>`.
///
/// This is a helper function that calls `Box::new(yourFuture) as Box<dyn GpuFuture + Send +
/// Sync>`.
#[inline]
fn boxed_send_sync(self) -> Box<dyn GpuFuture + Send + Sync>
where
Self: Sized + Send + Sync + 'static,
{
Box::new(self) as _
}
}
unsafe impl<F: ?Sized> GpuFuture for Box<F>
where
F: GpuFuture,
{
fn cleanup_finished(&mut self) {
(**self).cleanup_finished()
}
unsafe fn build_submission(&self) -> Result<SubmitAnyBuilder, Validated<VulkanError>> {
(**self).build_submission()
}
fn flush(&self) -> Result<(), Validated<VulkanError>> {
(**self).flush()
}
unsafe fn signal_finished(&self) {
(**self).signal_finished()
}
fn queue_change_allowed(&self) -> bool {
(**self).queue_change_allowed()
}
fn queue(&self) -> Option<Arc<Queue>> {
(**self).queue()
}
fn check_buffer_access(
&self,
buffer: &Buffer,
range: Range<DeviceSize>,
exclusive: bool,
queue: &Queue,
) -> Result<(), AccessCheckError> {
(**self).check_buffer_access(buffer, range, exclusive, queue)
}
fn check_image_access(
&self,
image: &Image,
range: Range<DeviceSize>,
exclusive: bool,
expected_layout: ImageLayout,
queue: &Queue,
) -> Result<(), AccessCheckError> {
(**self).check_image_access(image, range, exclusive, expected_layout, queue)
}
#[inline]
fn check_swapchain_image_acquired(
&self,
swapchain: &Swapchain,
image_index: u32,
before: bool,
) -> Result<(), AccessCheckError> {
(**self).check_swapchain_image_acquired(swapchain, image_index, before)
}
}
/// Contains all the possible submission builders.
#[derive(Debug)]
pub enum SubmitAnyBuilder {
Empty,
SemaphoresWait(SmallVec<[Arc<Semaphore>; 8]>),
CommandBuffer(SubmitInfo, Option<Arc<Fence>>),
QueuePresent(PresentInfo),
BindSparse(SmallVec<[BindSparseInfo; 1]>, Option<Arc<Fence>>),
}
impl SubmitAnyBuilder {
/// Returns true if equal to `SubmitAnyBuilder::Empty`.
#[inline]
pub fn is_empty(&self) -> bool {
matches!(self, SubmitAnyBuilder::Empty)
}
}
/// Access to a resource was denied.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum AccessError {
/// The resource is already in use, and there is no tracking of concurrent usages.
AlreadyInUse,
UnexpectedImageLayout {
allowed: ImageLayout,
requested: ImageLayout,
},
/// Trying to use an image without transitioning it from the "undefined" or "preinitialized"
/// layouts first.
ImageNotInitialized {
/// The layout that was requested for the image.
requested: ImageLayout,
},
/// Trying to use a swapchain image without depending on a corresponding acquire image future.
SwapchainImageNotAcquired,
}
impl Error for AccessError {}
impl Display for AccessError {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
let value = match self {
AccessError::AlreadyInUse => {
"the resource is already in use, and there is no tracking of concurrent usages"
}
AccessError::UnexpectedImageLayout { allowed, requested } => {
return write!(
f,
"unexpected image layout: requested {:?}, allowed {:?}",
allowed, requested
)
}
AccessError::ImageNotInitialized { .. } => {
"trying to use an image without transitioning it from the undefined or \
preinitialized layouts first"
}
AccessError::SwapchainImageNotAcquired => {
"trying to use a swapchain image without depending on a corresponding acquire \
image future"
}
};
write!(f, "{}", value,)
}
}
/// Error that can happen when checking whether we have access to a resource.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum AccessCheckError {
/// Access to the resource has been denied.
Denied(AccessError),
/// The resource is unknown, therefore we cannot possibly answer whether we have access or not.
Unknown,
}
impl Error for AccessCheckError {}
impl Display for AccessCheckError {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
match self {
AccessCheckError::Denied(err) => {
write!(f, "access to the resource has been denied: {}", err)
}
AccessCheckError::Unknown => write!(f, "the resource is unknown"),
}
}
}
impl From<AccessError> for AccessCheckError {
fn from(err: AccessError) -> AccessCheckError {
AccessCheckError::Denied(err)
}
}