mirror of https://github.com/torvalds/linux.git
107 lines
3.2 KiB
Rust
107 lines
3.2 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2024 Google LLC.
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//! Utilities for working with `struct poll_table`.
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use crate::{
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bindings,
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fs::File,
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prelude::*,
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sync::{CondVar, LockClassKey},
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};
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use core::{marker::PhantomData, ops::Deref};
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/// Creates a [`PollCondVar`] initialiser with the given name and a newly-created lock class.
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#[macro_export]
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macro_rules! new_poll_condvar {
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($($name:literal)?) => {
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$crate::sync::poll::PollCondVar::new(
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$crate::optional_name!($($name)?), $crate::static_lock_class!()
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)
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};
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}
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/// Wraps the kernel's `poll_table`.
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///
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/// # Invariants
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///
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/// The pointer must be null or reference a valid `poll_table`.
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#[repr(transparent)]
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pub struct PollTable<'a> {
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table: *mut bindings::poll_table,
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_lifetime: PhantomData<&'a bindings::poll_table>,
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}
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impl<'a> PollTable<'a> {
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/// Creates a [`PollTable`] from a valid pointer.
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///
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/// # Safety
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///
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/// The pointer must be null or reference a valid `poll_table` for the duration of `'a`.
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pub unsafe fn from_raw(table: *mut bindings::poll_table) -> Self {
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// INVARIANTS: The safety requirements are the same as the struct invariants.
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PollTable {
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table,
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_lifetime: PhantomData,
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}
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}
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/// Register this [`PollTable`] with the provided [`PollCondVar`], so that it can be notified
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/// using the condition variable.
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pub fn register_wait(&self, file: &File, cv: &PollCondVar) {
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// SAFETY:
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// * `file.as_ptr()` references a valid file for the duration of this call.
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// * `self.table` is null or references a valid poll_table for the duration of this call.
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// * Since `PollCondVar` is pinned, its destructor is guaranteed to run before the memory
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// containing `cv.wait_queue_head` is invalidated. Since the destructor clears all
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// waiters and then waits for an rcu grace period, it's guaranteed that
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// `cv.wait_queue_head` remains valid for at least an rcu grace period after the removal
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// of the last waiter.
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unsafe { bindings::poll_wait(file.as_ptr(), cv.wait_queue_head.get(), self.table) }
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}
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}
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/// A wrapper around [`CondVar`] that makes it usable with [`PollTable`].
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///
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/// [`CondVar`]: crate::sync::CondVar
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#[pin_data(PinnedDrop)]
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pub struct PollCondVar {
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#[pin]
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inner: CondVar,
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}
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impl PollCondVar {
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/// Constructs a new condvar initialiser.
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pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self> {
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pin_init!(Self {
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inner <- CondVar::new(name, key),
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})
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}
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}
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// Make the `CondVar` methods callable on `PollCondVar`.
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impl Deref for PollCondVar {
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type Target = CondVar;
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fn deref(&self) -> &CondVar {
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&self.inner
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}
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}
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#[pinned_drop]
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impl PinnedDrop for PollCondVar {
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#[inline]
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fn drop(self: Pin<&mut Self>) {
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// Clear anything registered using `register_wait`.
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//
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// SAFETY: The pointer points at a valid `wait_queue_head`.
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unsafe { bindings::__wake_up_pollfree(self.inner.wait_queue_head.get()) };
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// Wait for epoll items to be properly removed.
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//
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// SAFETY: Just an FFI call.
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unsafe { bindings::synchronize_rcu() };
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}
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}
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