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webgpu: Use WGPU poller thread for poll_all_devices (#32266)
* Use special WGPU poller thread for poll_all_devices * Switch to latest wgpu This is required to fix some deadlocks. * non-blocking poll unconditionally * small fixes
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| Original file line number | Diff line number | Diff line change |
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| /* This Source Code Form is subject to the terms of the Mozilla Public | ||
| * License, v. 2.0. If a copy of the MPL was not distributed with this | ||
| * file, You can obtain one at https://mozilla.org/MPL/2.0/. */ | ||
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| //! Data and main loop of WGPU poll thread. | ||
| //! | ||
| //! This is roughly based on <https://github.com/LucentFlux/wgpu-async/blob/1322c7e3fcdfc1865a472c7bbbf0e2e06dcf4da8/src/wgpu_future.rs> | ||
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| use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering}; | ||
| use std::sync::Arc; | ||
| use std::thread::JoinHandle; | ||
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| use log::warn; | ||
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| use crate::wgc::global::Global; | ||
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| /// Polls devices while there is something to poll. | ||
| /// | ||
| /// This objects corresponds to a thread that parks itself when there is no work, | ||
| /// waiting on it, and then calls `poll_all_devices` repeatedly to block. | ||
| /// | ||
| /// The thread dies when this object is dropped, and all work in submission is done. | ||
| /// | ||
| /// ## Example | ||
| /// ```no_run | ||
| /// let token = self.poller.token(); // create a new token | ||
| /// let callback = SubmittedWorkDoneClosure::from_rust(Box::from(move || { | ||
| /// drop(token); // drop token as closure has been fired | ||
| /// // ... | ||
| /// })); | ||
| /// let result = gfx_select!(queue_id => global.queue_on_submitted_work_done(queue_id, callback)); | ||
| /// self.poller.wake(); // wake poller thread to actually poll | ||
| /// ``` | ||
| #[derive(Debug)] | ||
| pub(crate) struct Poller { | ||
| /// The number of closures that still needs to be fired. | ||
| /// When this is 0, the thread can park itself. | ||
| work_count: Arc<AtomicUsize>, | ||
| /// True if thread should die after all work in submission is done | ||
| is_done: Arc<AtomicBool>, | ||
| /// Handle to the WGPU poller thread (to be used for unparking the thread) | ||
| handle: Option<JoinHandle<()>>, | ||
| } | ||
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| #[inline] | ||
| fn poll_all_devices(global: &Arc<Global>, more_work: &mut bool, force_wait: bool) { | ||
| match global.poll_all_devices(force_wait) { | ||
| Ok(all_queue_empty) => *more_work = !all_queue_empty, | ||
| Err(e) => warn!("Poller thread got `{e}` on poll_all_devices."), | ||
| } | ||
| } | ||
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| impl Poller { | ||
| pub(crate) fn new(global: Arc<Global>) -> Self { | ||
| let work_count = Arc::new(AtomicUsize::new(0)); | ||
| let is_done = Arc::new(AtomicBool::new(false)); | ||
| let work = work_count.clone(); | ||
| let done = is_done.clone(); | ||
| Self { | ||
| work_count, | ||
| is_done, | ||
| handle: Some( | ||
| std::thread::Builder::new() | ||
| .name("WGPU poller".into()) | ||
| .spawn(move || { | ||
| while !done.load(Ordering::Acquire) { | ||
| let mut more_work = false; | ||
| // Do non-blocking poll unconditionally | ||
| // so every `ẁake` (even spurious) will do at least one poll. | ||
| // this is mostly useful for stuff that is deferred | ||
| // to maintain calls in wgpu (device resource destruction) | ||
| poll_all_devices(&global, &mut more_work, false); | ||
| while more_work || work.load(Ordering::Acquire) != 0 { | ||
| poll_all_devices(&global, &mut more_work, true); | ||
| } | ||
| std::thread::park(); //TODO: should we use timeout here | ||
| } | ||
| }) | ||
| .expect("Spawning thread should not fail"), | ||
| ), | ||
| } | ||
| } | ||
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| /// Creates a token of work | ||
| pub(crate) fn token(&self) -> WorkToken { | ||
| let prev = self.work_count.fetch_add(1, Ordering::AcqRel); | ||
| debug_assert!( | ||
| prev < usize::MAX, | ||
| "cannot have more than `usize::MAX` outstanding operations on the GPU" | ||
| ); | ||
| WorkToken { | ||
| work_count: Arc::clone(&self.work_count), | ||
| } | ||
| } | ||
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| /// Wakes the poller thread to start polling. | ||
| pub(crate) fn wake(&self) { | ||
| self.handle | ||
| .as_ref() | ||
| .expect("Poller thread does not exist!") | ||
| .thread() | ||
| .unpark(); | ||
| } | ||
| } | ||
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| impl Drop for Poller { | ||
| fn drop(&mut self) { | ||
| self.is_done.store(true, Ordering::Release); | ||
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| let handle = self.handle.take().expect("Poller dropped twice"); | ||
| handle.thread().unpark(); | ||
| handle.join().expect("Poller thread panicked"); | ||
| } | ||
| } | ||
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| /// RAII indicating that there is some work enqueued (closure to be fired), | ||
| /// while this token is held. | ||
| pub(crate) struct WorkToken { | ||
| work_count: Arc<AtomicUsize>, | ||
| } | ||
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| impl Drop for WorkToken { | ||
| fn drop(&mut self) { | ||
| self.work_count.fetch_sub(1, Ordering::AcqRel); | ||
| } | ||
| } |
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