kernel/
workqueue.rs

1// SPDX-License-Identifier: GPL-2.0
2
3//! Work queues.
4//!
5//! This file has two components: The raw work item API, and the safe work item API.
6//!
7//! One pattern that is used in both APIs is the `ID` const generic, which exists to allow a single
8//! type to define multiple `work_struct` fields. This is done by choosing an id for each field,
9//! and using that id to specify which field you wish to use. (The actual value doesn't matter, as
10//! long as you use different values for different fields of the same struct.) Since these IDs are
11//! generic, they are used only at compile-time, so they shouldn't exist in the final binary.
12//!
13//! # The raw API
14//!
15//! The raw API consists of the [`RawWorkItem`] trait, where the work item needs to provide an
16//! arbitrary function that knows how to enqueue the work item. It should usually not be used
17//! directly, but if you want to, you can use it without using the pieces from the safe API.
18//!
19//! # The safe API
20//!
21//! The safe API is used via the [`Work`] struct and [`WorkItem`] traits. Furthermore, it also
22//! includes a trait called [`WorkItemPointer`], which is usually not used directly by the user.
23//!
24//!  * The [`Work`] struct is the Rust wrapper for the C `work_struct` type.
25//!  * The [`WorkItem`] trait is implemented for structs that can be enqueued to a workqueue.
26//!  * The [`WorkItemPointer`] trait is implemented for the pointer type that points at a something
27//!    that implements [`WorkItem`].
28//!
29//! ## Examples
30//!
31//! This example defines a struct that holds an integer and can be scheduled on the workqueue. When
32//! the struct is executed, it will print the integer. Since there is only one `work_struct` field,
33//! we do not need to specify ids for the fields.
34//!
35//! ```
36//! use kernel::sync::Arc;
37//! use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem};
38//!
39//! #[pin_data]
40//! struct MyStruct {
41//!     value: i32,
42//!     #[pin]
43//!     work: Work<MyStruct>,
44//! }
45//!
46//! impl_has_work! {
47//!     impl HasWork<Self> for MyStruct { self.work }
48//! }
49//!
50//! impl MyStruct {
51//!     fn new(value: i32) -> Result<Arc<Self>> {
52//!         Arc::pin_init(pin_init!(MyStruct {
53//!             value,
54//!             work <- new_work!("MyStruct::work"),
55//!         }), GFP_KERNEL)
56//!     }
57//! }
58//!
59//! impl WorkItem for MyStruct {
60//!     type Pointer = Arc<MyStruct>;
61//!
62//!     fn run(this: Arc<MyStruct>) {
63//!         pr_info!("The value is: {}\n", this.value);
64//!     }
65//! }
66//!
67//! /// This method will enqueue the struct for execution on the system workqueue, where its value
68//! /// will be printed.
69//! fn print_later(val: Arc<MyStruct>) {
70//!     let _ = workqueue::system().enqueue(val);
71//! }
72//! # print_later(MyStruct::new(42).unwrap());
73//! ```
74//!
75//! The following example shows how multiple `work_struct` fields can be used:
76//!
77//! ```
78//! use kernel::sync::Arc;
79//! use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem};
80//!
81//! #[pin_data]
82//! struct MyStruct {
83//!     value_1: i32,
84//!     value_2: i32,
85//!     #[pin]
86//!     work_1: Work<MyStruct, 1>,
87//!     #[pin]
88//!     work_2: Work<MyStruct, 2>,
89//! }
90//!
91//! impl_has_work! {
92//!     impl HasWork<Self, 1> for MyStruct { self.work_1 }
93//!     impl HasWork<Self, 2> for MyStruct { self.work_2 }
94//! }
95//!
96//! impl MyStruct {
97//!     fn new(value_1: i32, value_2: i32) -> Result<Arc<Self>> {
98//!         Arc::pin_init(pin_init!(MyStruct {
99//!             value_1,
100//!             value_2,
101//!             work_1 <- new_work!("MyStruct::work_1"),
102//!             work_2 <- new_work!("MyStruct::work_2"),
103//!         }), GFP_KERNEL)
104//!     }
105//! }
106//!
107//! impl WorkItem<1> for MyStruct {
108//!     type Pointer = Arc<MyStruct>;
109//!
110//!     fn run(this: Arc<MyStruct>) {
111//!         pr_info!("The value is: {}\n", this.value_1);
112//!     }
113//! }
114//!
115//! impl WorkItem<2> for MyStruct {
116//!     type Pointer = Arc<MyStruct>;
117//!
118//!     fn run(this: Arc<MyStruct>) {
119//!         pr_info!("The second value is: {}\n", this.value_2);
120//!     }
121//! }
122//!
123//! fn print_1_later(val: Arc<MyStruct>) {
124//!     let _ = workqueue::system().enqueue::<Arc<MyStruct>, 1>(val);
125//! }
126//!
127//! fn print_2_later(val: Arc<MyStruct>) {
128//!     let _ = workqueue::system().enqueue::<Arc<MyStruct>, 2>(val);
129//! }
130//! # print_1_later(MyStruct::new(24, 25).unwrap());
131//! # print_2_later(MyStruct::new(41, 42).unwrap());
132//! ```
133//!
134//! This example shows how you can schedule delayed work items:
135//!
136//! ```
137//! use kernel::sync::Arc;
138//! use kernel::workqueue::{self, impl_has_delayed_work, new_delayed_work, DelayedWork, WorkItem};
139//!
140//! #[pin_data]
141//! struct MyStruct {
142//!     value: i32,
143//!     #[pin]
144//!     work: DelayedWork<MyStruct>,
145//! }
146//!
147//! impl_has_delayed_work! {
148//!     impl HasDelayedWork<Self> for MyStruct { self.work }
149//! }
150//!
151//! impl MyStruct {
152//!     fn new(value: i32) -> Result<Arc<Self>> {
153//!         Arc::pin_init(
154//!             pin_init!(MyStruct {
155//!                 value,
156//!                 work <- new_delayed_work!("MyStruct::work"),
157//!             }),
158//!             GFP_KERNEL,
159//!         )
160//!     }
161//! }
162//!
163//! impl WorkItem for MyStruct {
164//!     type Pointer = Arc<MyStruct>;
165//!
166//!     fn run(this: Arc<MyStruct>) {
167//!         pr_info!("The value is: {}\n", this.value);
168//!     }
169//! }
170//!
171//! /// This method will enqueue the struct for execution on the system workqueue, where its value
172//! /// will be printed 12 jiffies later.
173//! fn print_later(val: Arc<MyStruct>) {
174//!     let _ = workqueue::system().enqueue_delayed(val, 12);
175//! }
176//!
177//! /// It is also possible to use the ordinary `enqueue` method together with `DelayedWork`. This
178//! /// is equivalent to calling `enqueue_delayed` with a delay of zero.
179//! fn print_now(val: Arc<MyStruct>) {
180//!     let _ = workqueue::system().enqueue(val);
181//! }
182//! # print_later(MyStruct::new(42).unwrap());
183//! # print_now(MyStruct::new(42).unwrap());
184//! ```
185//!
186//! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h)
187
188use crate::{
189    alloc::{AllocError, Flags},
190    container_of,
191    prelude::*,
192    sync::Arc,
193    sync::LockClassKey,
194    time::Jiffies,
195    types::Opaque,
196};
197use core::marker::PhantomData;
198
199/// Creates a [`Work`] initialiser with the given name and a newly-created lock class.
200#[macro_export]
201macro_rules! new_work {
202    ($($name:literal)?) => {
203        $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
204    };
205}
206pub use new_work;
207
208/// Creates a [`DelayedWork`] initialiser with the given name and a newly-created lock class.
209#[macro_export]
210macro_rules! new_delayed_work {
211    () => {
212        $crate::workqueue::DelayedWork::new(
213            $crate::optional_name!(),
214            $crate::static_lock_class!(),
215            $crate::c_str!(::core::concat!(
216                ::core::file!(),
217                ":",
218                ::core::line!(),
219                "_timer"
220            )),
221            $crate::static_lock_class!(),
222        )
223    };
224    ($name:literal) => {
225        $crate::workqueue::DelayedWork::new(
226            $crate::c_str!($name),
227            $crate::static_lock_class!(),
228            $crate::c_str!(::core::concat!($name, "_timer")),
229            $crate::static_lock_class!(),
230        )
231    };
232}
233pub use new_delayed_work;
234
235/// A kernel work queue.
236///
237/// Wraps the kernel's C `struct workqueue_struct`.
238///
239/// It allows work items to be queued to run on thread pools managed by the kernel. Several are
240/// always available, for example, `system`, `system_highpri`, `system_long`, etc.
241#[repr(transparent)]
242pub struct Queue(Opaque<bindings::workqueue_struct>);
243
244// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
245unsafe impl Send for Queue {}
246// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
247unsafe impl Sync for Queue {}
248
249impl Queue {
250    /// Use the provided `struct workqueue_struct` with Rust.
251    ///
252    /// # Safety
253    ///
254    /// The caller must ensure that the provided raw pointer is not dangling, that it points at a
255    /// valid workqueue, and that it remains valid until the end of `'a`.
256    pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue {
257        // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The
258        // caller promises that the pointer is not dangling.
259        unsafe { &*ptr.cast::<Queue>() }
260    }
261
262    /// Enqueues a work item.
263    ///
264    /// This may fail if the work item is already enqueued in a workqueue.
265    ///
266    /// The work item will be submitted using `WORK_CPU_UNBOUND`.
267    pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
268    where
269        W: RawWorkItem<ID> + Send + 'static,
270    {
271        let queue_ptr = self.0.get();
272
273        // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
274        // `__enqueue` requirements are not relevant since `W` is `Send` and static.
275        //
276        // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which
277        // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this
278        // closure.
279        //
280        // Furthermore, if the C workqueue code accesses the pointer after this call to
281        // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on`
282        // will have returned true. In this case, `__enqueue` promises that the raw pointer will
283        // stay valid until we call the function pointer in the `work_struct`, so the access is ok.
284        unsafe {
285            w.__enqueue(move |work_ptr| {
286                bindings::queue_work_on(
287                    bindings::wq_misc_consts_WORK_CPU_UNBOUND as ffi::c_int,
288                    queue_ptr,
289                    work_ptr,
290                )
291            })
292        }
293    }
294
295    /// Enqueues a delayed work item.
296    ///
297    /// This may fail if the work item is already enqueued in a workqueue.
298    ///
299    /// The work item will be submitted using `WORK_CPU_UNBOUND`.
300    pub fn enqueue_delayed<W, const ID: u64>(&self, w: W, delay: Jiffies) -> W::EnqueueOutput
301    where
302        W: RawDelayedWorkItem<ID> + Send + 'static,
303    {
304        let queue_ptr = self.0.get();
305
306        // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
307        // `__enqueue` requirements are not relevant since `W` is `Send` and static.
308        //
309        // The call to `bindings::queue_delayed_work_on` will dereference the provided raw pointer,
310        // which is ok because `__enqueue` guarantees that the pointer is valid for the duration of
311        // this closure, and the safety requirements of `RawDelayedWorkItem` expands this
312        // requirement to apply to the entire `delayed_work`.
313        //
314        // Furthermore, if the C workqueue code accesses the pointer after this call to
315        // `__enqueue`, then the work item was successfully enqueued, and
316        // `bindings::queue_delayed_work_on` will have returned true. In this case, `__enqueue`
317        // promises that the raw pointer will stay valid until we call the function pointer in the
318        // `work_struct`, so the access is ok.
319        unsafe {
320            w.__enqueue(move |work_ptr| {
321                bindings::queue_delayed_work_on(
322                    bindings::wq_misc_consts_WORK_CPU_UNBOUND as ffi::c_int,
323                    queue_ptr,
324                    container_of!(work_ptr, bindings::delayed_work, work),
325                    delay,
326                )
327            })
328        }
329    }
330
331    /// Tries to spawn the given function or closure as a work item.
332    ///
333    /// This method can fail because it allocates memory to store the work item.
334    pub fn try_spawn<T: 'static + Send + FnOnce()>(
335        &self,
336        flags: Flags,
337        func: T,
338    ) -> Result<(), AllocError> {
339        let init = pin_init!(ClosureWork {
340            work <- new_work!("Queue::try_spawn"),
341            func: Some(func),
342        });
343
344        self.enqueue(KBox::pin_init(init, flags).map_err(|_| AllocError)?);
345        Ok(())
346    }
347}
348
349/// A helper type used in [`try_spawn`].
350///
351/// [`try_spawn`]: Queue::try_spawn
352#[pin_data]
353struct ClosureWork<T> {
354    #[pin]
355    work: Work<ClosureWork<T>>,
356    func: Option<T>,
357}
358
359impl<T> ClosureWork<T> {
360    fn project(self: Pin<&mut Self>) -> &mut Option<T> {
361        // SAFETY: The `func` field is not structurally pinned.
362        unsafe { &mut self.get_unchecked_mut().func }
363    }
364}
365
366impl<T: FnOnce()> WorkItem for ClosureWork<T> {
367    type Pointer = Pin<KBox<Self>>;
368
369    fn run(mut this: Pin<KBox<Self>>) {
370        if let Some(func) = this.as_mut().project().take() {
371            (func)()
372        }
373    }
374}
375
376/// A raw work item.
377///
378/// This is the low-level trait that is designed for being as general as possible.
379///
380/// The `ID` parameter to this trait exists so that a single type can provide multiple
381/// implementations of this trait. For example, if a struct has multiple `work_struct` fields, then
382/// you will implement this trait once for each field, using a different id for each field. The
383/// actual value of the id is not important as long as you use different ids for different fields
384/// of the same struct. (Fields of different structs need not use different ids.)
385///
386/// Note that the id is used only to select the right method to call during compilation. It won't be
387/// part of the final executable.
388///
389/// # Safety
390///
391/// Implementers must ensure that any pointers passed to a `queue_work_on` closure by [`__enqueue`]
392/// remain valid for the duration specified in the guarantees section of the documentation for
393/// [`__enqueue`].
394///
395/// [`__enqueue`]: RawWorkItem::__enqueue
396pub unsafe trait RawWorkItem<const ID: u64> {
397    /// The return type of [`Queue::enqueue`].
398    type EnqueueOutput;
399
400    /// Enqueues this work item on a queue using the provided `queue_work_on` method.
401    ///
402    /// # Guarantees
403    ///
404    /// If this method calls the provided closure, then the raw pointer is guaranteed to point at a
405    /// valid `work_struct` for the duration of the call to the closure. If the closure returns
406    /// true, then it is further guaranteed that the pointer remains valid until someone calls the
407    /// function pointer stored in the `work_struct`.
408    ///
409    /// # Safety
410    ///
411    /// The provided closure may only return `false` if the `work_struct` is already in a workqueue.
412    ///
413    /// If the work item type is annotated with any lifetimes, then you must not call the function
414    /// pointer after any such lifetime expires. (Never calling the function pointer is okay.)
415    ///
416    /// If the work item type is not [`Send`], then the function pointer must be called on the same
417    /// thread as the call to `__enqueue`.
418    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
419    where
420        F: FnOnce(*mut bindings::work_struct) -> bool;
421}
422
423/// A raw delayed work item.
424///
425/// # Safety
426///
427/// If the `__enqueue` method in the `RawWorkItem` implementation calls the closure, then the
428/// provided pointer must point at the `work` field of a valid `delayed_work`, and the guarantees
429/// that `__enqueue` provides about accessing the `work_struct` must also apply to the rest of the
430/// `delayed_work` struct.
431pub unsafe trait RawDelayedWorkItem<const ID: u64>: RawWorkItem<ID> {}
432
433/// Defines the method that should be called directly when a work item is executed.
434///
435/// This trait is implemented by `Pin<KBox<T>>` and [`Arc<T>`], and is mainly intended to be
436/// implemented for smart pointer types. For your own structs, you would implement [`WorkItem`]
437/// instead. The [`run`] method on this trait will usually just perform the appropriate
438/// `container_of` translation and then call into the [`run`][WorkItem::run] method from the
439/// [`WorkItem`] trait.
440///
441/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
442///
443/// # Safety
444///
445/// Implementers must ensure that [`__enqueue`] uses a `work_struct` initialized with the [`run`]
446/// method of this trait as the function pointer.
447///
448/// [`__enqueue`]: RawWorkItem::__enqueue
449/// [`run`]: WorkItemPointer::run
450pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
451    /// Run this work item.
452    ///
453    /// # Safety
454    ///
455    /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
456    /// where the `queue_work_on` closure returned true, and the pointer must still be valid.
457    ///
458    /// [`__enqueue`]: RawWorkItem::__enqueue
459    unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
460}
461
462/// Defines the method that should be called when this work item is executed.
463///
464/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
465pub trait WorkItem<const ID: u64 = 0> {
466    /// The pointer type that this struct is wrapped in. This will typically be `Arc<Self>` or
467    /// `Pin<KBox<Self>>`.
468    type Pointer: WorkItemPointer<ID>;
469
470    /// The method that should be called when this work item is executed.
471    fn run(this: Self::Pointer);
472}
473
474/// Links for a work item.
475///
476/// This struct contains a function pointer to the [`run`] function from the [`WorkItemPointer`]
477/// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue.
478///
479/// Wraps the kernel's C `struct work_struct`.
480///
481/// This is a helper type used to associate a `work_struct` with the [`WorkItem`] that uses it.
482///
483/// [`run`]: WorkItemPointer::run
484#[pin_data]
485#[repr(transparent)]
486pub struct Work<T: ?Sized, const ID: u64 = 0> {
487    #[pin]
488    work: Opaque<bindings::work_struct>,
489    _inner: PhantomData<T>,
490}
491
492// SAFETY: Kernel work items are usable from any thread.
493//
494// We do not need to constrain `T` since the work item does not actually contain a `T`.
495unsafe impl<T: ?Sized, const ID: u64> Send for Work<T, ID> {}
496// SAFETY: Kernel work items are usable from any thread.
497//
498// We do not need to constrain `T` since the work item does not actually contain a `T`.
499unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
500
501impl<T: ?Sized, const ID: u64> Work<T, ID> {
502    /// Creates a new instance of [`Work`].
503    #[inline]
504    pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self>
505    where
506        T: WorkItem<ID>,
507    {
508        pin_init!(Self {
509            work <- Opaque::ffi_init(|slot| {
510                // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as
511                // the work item function.
512                unsafe {
513                    bindings::init_work_with_key(
514                        slot,
515                        Some(T::Pointer::run),
516                        false,
517                        name.as_char_ptr(),
518                        key.as_ptr(),
519                    )
520                }
521            }),
522            _inner: PhantomData,
523        })
524    }
525
526    /// Get a pointer to the inner `work_struct`.
527    ///
528    /// # Safety
529    ///
530    /// The provided pointer must not be dangling and must be properly aligned. (But the memory
531    /// need not be initialized.)
532    #[inline]
533    pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
534        // SAFETY: The caller promises that the pointer is aligned and not dangling.
535        //
536        // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
537        // the compiler does not complain that the `work` field is unused.
538        unsafe { Opaque::cast_into(core::ptr::addr_of!((*ptr).work)) }
539    }
540}
541
542/// Declares that a type contains a [`Work<T, ID>`].
543///
544/// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro
545/// like this:
546///
547/// ```no_run
548/// use kernel::workqueue::{impl_has_work, Work};
549///
550/// struct MyWorkItem {
551///     work_field: Work<MyWorkItem, 1>,
552/// }
553///
554/// impl_has_work! {
555///     impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field }
556/// }
557/// ```
558///
559/// Note that since the [`Work`] type is annotated with an id, you can have several `work_struct`
560/// fields by using a different id for each one.
561///
562/// # Safety
563///
564/// The methods [`raw_get_work`] and [`work_container_of`] must return valid pointers and must be
565/// true inverses of each other; that is, they must satisfy the following invariants:
566/// - `work_container_of(raw_get_work(ptr)) == ptr` for any `ptr: *mut Self`.
567/// - `raw_get_work(work_container_of(ptr)) == ptr` for any `ptr: *mut Work<T, ID>`.
568///
569/// [`impl_has_work!`]: crate::impl_has_work
570/// [`raw_get_work`]: HasWork::raw_get_work
571/// [`work_container_of`]: HasWork::work_container_of
572pub unsafe trait HasWork<T, const ID: u64 = 0> {
573    /// Returns a pointer to the [`Work<T, ID>`] field.
574    ///
575    /// # Safety
576    ///
577    /// The provided pointer must point at a valid struct of type `Self`.
578    unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID>;
579
580    /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
581    ///
582    /// # Safety
583    ///
584    /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
585    unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self;
586}
587
588/// Used to safely implement the [`HasWork<T, ID>`] trait.
589///
590/// # Examples
591///
592/// ```
593/// use kernel::sync::Arc;
594/// use kernel::workqueue::{self, impl_has_work, Work};
595///
596/// struct MyStruct<'a, T, const N: usize> {
597///     work_field: Work<MyStruct<'a, T, N>, 17>,
598///     f: fn(&'a [T; N]),
599/// }
600///
601/// impl_has_work! {
602///     impl{'a, T, const N: usize} HasWork<MyStruct<'a, T, N>, 17>
603///     for MyStruct<'a, T, N> { self.work_field }
604/// }
605/// ```
606#[macro_export]
607macro_rules! impl_has_work {
608    ($(impl$({$($generics:tt)*})?
609       HasWork<$work_type:ty $(, $id:tt)?>
610       for $self:ty
611       { self.$field:ident }
612    )*) => {$(
613        // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
614        // type.
615        unsafe impl$(<$($generics)+>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self {
616            #[inline]
617            unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
618                // SAFETY: The caller promises that the pointer is not dangling.
619                unsafe {
620                    ::core::ptr::addr_of_mut!((*ptr).$field)
621                }
622            }
623
624            #[inline]
625            unsafe fn work_container_of(
626                ptr: *mut $crate::workqueue::Work<$work_type $(, $id)?>,
627            ) -> *mut Self {
628                // SAFETY: The caller promises that the pointer points at a field of the right type
629                // in the right kind of struct.
630                unsafe { $crate::container_of!(ptr, Self, $field) }
631            }
632        }
633    )*};
634}
635pub use impl_has_work;
636
637impl_has_work! {
638    impl{T} HasWork<Self> for ClosureWork<T> { self.work }
639}
640
641/// Links for a delayed work item.
642///
643/// This struct contains a function pointer to the [`run`] function from the [`WorkItemPointer`]
644/// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue in
645/// a delayed manner.
646///
647/// Wraps the kernel's C `struct delayed_work`.
648///
649/// This is a helper type used to associate a `delayed_work` with the [`WorkItem`] that uses it.
650///
651/// [`run`]: WorkItemPointer::run
652#[pin_data]
653#[repr(transparent)]
654pub struct DelayedWork<T: ?Sized, const ID: u64 = 0> {
655    #[pin]
656    dwork: Opaque<bindings::delayed_work>,
657    _inner: PhantomData<T>,
658}
659
660// SAFETY: Kernel work items are usable from any thread.
661//
662// We do not need to constrain `T` since the work item does not actually contain a `T`.
663unsafe impl<T: ?Sized, const ID: u64> Send for DelayedWork<T, ID> {}
664// SAFETY: Kernel work items are usable from any thread.
665//
666// We do not need to constrain `T` since the work item does not actually contain a `T`.
667unsafe impl<T: ?Sized, const ID: u64> Sync for DelayedWork<T, ID> {}
668
669impl<T: ?Sized, const ID: u64> DelayedWork<T, ID> {
670    /// Creates a new instance of [`DelayedWork`].
671    #[inline]
672    pub fn new(
673        work_name: &'static CStr,
674        work_key: Pin<&'static LockClassKey>,
675        timer_name: &'static CStr,
676        timer_key: Pin<&'static LockClassKey>,
677    ) -> impl PinInit<Self>
678    where
679        T: WorkItem<ID>,
680    {
681        pin_init!(Self {
682            dwork <- Opaque::ffi_init(|slot: *mut bindings::delayed_work| {
683                // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as
684                // the work item function.
685                unsafe {
686                    bindings::init_work_with_key(
687                        core::ptr::addr_of_mut!((*slot).work),
688                        Some(T::Pointer::run),
689                        false,
690                        work_name.as_char_ptr(),
691                        work_key.as_ptr(),
692                    )
693                }
694
695                // SAFETY: The `delayed_work_timer_fn` function pointer can be used here because
696                // the timer is embedded in a `struct delayed_work`, and only ever scheduled via
697                // the core workqueue code, and configured to run in irqsafe context.
698                unsafe {
699                    bindings::timer_init_key(
700                        core::ptr::addr_of_mut!((*slot).timer),
701                        Some(bindings::delayed_work_timer_fn),
702                        bindings::TIMER_IRQSAFE,
703                        timer_name.as_char_ptr(),
704                        timer_key.as_ptr(),
705                    )
706                }
707            }),
708            _inner: PhantomData,
709        })
710    }
711
712    /// Get a pointer to the inner `delayed_work`.
713    ///
714    /// # Safety
715    ///
716    /// The provided pointer must not be dangling and must be properly aligned. (But the memory
717    /// need not be initialized.)
718    #[inline]
719    pub unsafe fn raw_as_work(ptr: *const Self) -> *mut Work<T, ID> {
720        // SAFETY: The caller promises that the pointer is aligned and not dangling.
721        let dw: *mut bindings::delayed_work =
722            unsafe { Opaque::cast_into(core::ptr::addr_of!((*ptr).dwork)) };
723        // SAFETY: The caller promises that the pointer is aligned and not dangling.
724        let wrk: *mut bindings::work_struct = unsafe { core::ptr::addr_of_mut!((*dw).work) };
725        // CAST: Work and work_struct have compatible layouts.
726        wrk.cast()
727    }
728}
729
730/// Declares that a type contains a [`DelayedWork<T, ID>`].
731///
732/// # Safety
733///
734/// The `HasWork<T, ID>` implementation must return a `work_struct` that is stored in the `work`
735/// field of a `delayed_work` with the same access rules as the `work_struct`.
736pub unsafe trait HasDelayedWork<T, const ID: u64 = 0>: HasWork<T, ID> {}
737
738/// Used to safely implement the [`HasDelayedWork<T, ID>`] trait.
739///
740/// This macro also implements the [`HasWork`] trait, so you do not need to use [`impl_has_work!`]
741/// when using this macro.
742///
743/// # Examples
744///
745/// ```
746/// use kernel::sync::Arc;
747/// use kernel::workqueue::{self, impl_has_delayed_work, DelayedWork};
748///
749/// struct MyStruct<'a, T, const N: usize> {
750///     work_field: DelayedWork<MyStruct<'a, T, N>, 17>,
751///     f: fn(&'a [T; N]),
752/// }
753///
754/// impl_has_delayed_work! {
755///     impl{'a, T, const N: usize} HasDelayedWork<MyStruct<'a, T, N>, 17>
756///     for MyStruct<'a, T, N> { self.work_field }
757/// }
758/// ```
759#[macro_export]
760macro_rules! impl_has_delayed_work {
761    ($(impl$({$($generics:tt)*})?
762       HasDelayedWork<$work_type:ty $(, $id:tt)?>
763       for $self:ty
764       { self.$field:ident }
765    )*) => {$(
766        // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
767        // type.
768        unsafe impl$(<$($generics)+>)?
769            $crate::workqueue::HasDelayedWork<$work_type $(, $id)?> for $self {}
770
771        // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
772        // type.
773        unsafe impl$(<$($generics)+>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self {
774            #[inline]
775            unsafe fn raw_get_work(
776                ptr: *mut Self
777            ) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
778                // SAFETY: The caller promises that the pointer is not dangling.
779                let ptr: *mut $crate::workqueue::DelayedWork<$work_type $(, $id)?> = unsafe {
780                    ::core::ptr::addr_of_mut!((*ptr).$field)
781                };
782
783                // SAFETY: The caller promises that the pointer is not dangling.
784                unsafe { $crate::workqueue::DelayedWork::raw_as_work(ptr) }
785            }
786
787            #[inline]
788            unsafe fn work_container_of(
789                ptr: *mut $crate::workqueue::Work<$work_type $(, $id)?>,
790            ) -> *mut Self {
791                // SAFETY: The caller promises that the pointer points at a field of the right type
792                // in the right kind of struct.
793                let ptr = unsafe { $crate::workqueue::Work::raw_get(ptr) };
794
795                // SAFETY: The caller promises that the pointer points at a field of the right type
796                // in the right kind of struct.
797                let delayed_work = unsafe {
798                    $crate::container_of!(ptr, $crate::bindings::delayed_work, work)
799                };
800
801                let delayed_work: *mut $crate::workqueue::DelayedWork<$work_type $(, $id)?> =
802                    delayed_work.cast();
803
804                // SAFETY: The caller promises that the pointer points at a field of the right type
805                // in the right kind of struct.
806                unsafe { $crate::container_of!(delayed_work, Self, $field) }
807            }
808        }
809    )*};
810}
811pub use impl_has_delayed_work;
812
813// SAFETY: The `__enqueue` implementation in RawWorkItem uses a `work_struct` initialized with the
814// `run` method of this trait as the function pointer because:
815//   - `__enqueue` gets the `work_struct` from the `Work` field, using `T::raw_get_work`.
816//   - The only safe way to create a `Work` object is through `Work::new`.
817//   - `Work::new` makes sure that `T::Pointer::run` is passed to `init_work_with_key`.
818//   - Finally `Work` and `RawWorkItem` guarantee that the correct `Work` field
819//     will be used because of the ID const generic bound. This makes sure that `T::raw_get_work`
820//     uses the correct offset for the `Work` field, and `Work::new` picks the correct
821//     implementation of `WorkItemPointer` for `Arc<T>`.
822unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
823where
824    T: WorkItem<ID, Pointer = Self>,
825    T: HasWork<T, ID>,
826{
827    unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
828        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
829        let ptr = ptr.cast::<Work<T, ID>>();
830        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
831        let ptr = unsafe { T::work_container_of(ptr) };
832        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
833        let arc = unsafe { Arc::from_raw(ptr) };
834
835        T::run(arc)
836    }
837}
838
839// SAFETY: The `work_struct` raw pointer is guaranteed to be valid for the duration of the call to
840// the closure because we get it from an `Arc`, which means that the ref count will be at least 1,
841// and we don't drop the `Arc` ourselves. If `queue_work_on` returns true, it is further guaranteed
842// to be valid until a call to the function pointer in `work_struct` because we leak the memory it
843// points to, and only reclaim it if the closure returns false, or in `WorkItemPointer::run`, which
844// is what the function pointer in the `work_struct` must be pointing to, according to the safety
845// requirements of `WorkItemPointer`.
846unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>
847where
848    T: WorkItem<ID, Pointer = Self>,
849    T: HasWork<T, ID>,
850{
851    type EnqueueOutput = Result<(), Self>;
852
853    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
854    where
855        F: FnOnce(*mut bindings::work_struct) -> bool,
856    {
857        // Casting between const and mut is not a problem as long as the pointer is a raw pointer.
858        let ptr = Arc::into_raw(self).cast_mut();
859
860        // SAFETY: Pointers into an `Arc` point at a valid value.
861        let work_ptr = unsafe { T::raw_get_work(ptr) };
862        // SAFETY: `raw_get_work` returns a pointer to a valid value.
863        let work_ptr = unsafe { Work::raw_get(work_ptr) };
864
865        if queue_work_on(work_ptr) {
866            Ok(())
867        } else {
868            // SAFETY: The work queue has not taken ownership of the pointer.
869            Err(unsafe { Arc::from_raw(ptr) })
870        }
871    }
872}
873
874// SAFETY: By the safety requirements of `HasDelayedWork`, the `work_struct` returned by methods in
875// `HasWork` provides a `work_struct` that is the `work` field of a `delayed_work`, and the rest of
876// the `delayed_work` has the same access rules as its `work` field.
877unsafe impl<T, const ID: u64> RawDelayedWorkItem<ID> for Arc<T>
878where
879    T: WorkItem<ID, Pointer = Self>,
880    T: HasDelayedWork<T, ID>,
881{
882}
883
884// SAFETY: TODO.
885unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<KBox<T>>
886where
887    T: WorkItem<ID, Pointer = Self>,
888    T: HasWork<T, ID>,
889{
890    unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
891        // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
892        let ptr = ptr.cast::<Work<T, ID>>();
893        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
894        let ptr = unsafe { T::work_container_of(ptr) };
895        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
896        let boxed = unsafe { KBox::from_raw(ptr) };
897        // SAFETY: The box was already pinned when it was enqueued.
898        let pinned = unsafe { Pin::new_unchecked(boxed) };
899
900        T::run(pinned)
901    }
902}
903
904// SAFETY: TODO.
905unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<KBox<T>>
906where
907    T: WorkItem<ID, Pointer = Self>,
908    T: HasWork<T, ID>,
909{
910    type EnqueueOutput = ();
911
912    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
913    where
914        F: FnOnce(*mut bindings::work_struct) -> bool,
915    {
916        // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily
917        // remove the `Pin` wrapper.
918        let boxed = unsafe { Pin::into_inner_unchecked(self) };
919        let ptr = KBox::into_raw(boxed);
920
921        // SAFETY: Pointers into a `KBox` point at a valid value.
922        let work_ptr = unsafe { T::raw_get_work(ptr) };
923        // SAFETY: `raw_get_work` returns a pointer to a valid value.
924        let work_ptr = unsafe { Work::raw_get(work_ptr) };
925
926        if !queue_work_on(work_ptr) {
927            // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a
928            // workqueue.
929            unsafe { ::core::hint::unreachable_unchecked() }
930        }
931    }
932}
933
934// SAFETY: By the safety requirements of `HasDelayedWork`, the `work_struct` returned by methods in
935// `HasWork` provides a `work_struct` that is the `work` field of a `delayed_work`, and the rest of
936// the `delayed_work` has the same access rules as its `work` field.
937unsafe impl<T, const ID: u64> RawDelayedWorkItem<ID> for Pin<KBox<T>>
938where
939    T: WorkItem<ID, Pointer = Self>,
940    T: HasDelayedWork<T, ID>,
941{
942}
943
944/// Returns the system work queue (`system_wq`).
945///
946/// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
947/// users which expect relatively short queue flush time.
948///
949/// Callers shouldn't queue work items which can run for too long.
950pub fn system() -> &'static Queue {
951    // SAFETY: `system_wq` is a C global, always available.
952    unsafe { Queue::from_raw(bindings::system_wq) }
953}
954
955/// Returns the system high-priority work queue (`system_highpri_wq`).
956///
957/// It is similar to the one returned by [`system`] but for work items which require higher
958/// scheduling priority.
959pub fn system_highpri() -> &'static Queue {
960    // SAFETY: `system_highpri_wq` is a C global, always available.
961    unsafe { Queue::from_raw(bindings::system_highpri_wq) }
962}
963
964/// Returns the system work queue for potentially long-running work items (`system_long_wq`).
965///
966/// It is similar to the one returned by [`system`] but may host long running work items. Queue
967/// flushing might take relatively long.
968pub fn system_long() -> &'static Queue {
969    // SAFETY: `system_long_wq` is a C global, always available.
970    unsafe { Queue::from_raw(bindings::system_long_wq) }
971}
972
973/// Returns the system unbound work queue (`system_unbound_wq`).
974///
975/// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
976/// are executed immediately as long as `max_active` limit is not reached and resources are
977/// available.
978pub fn system_unbound() -> &'static Queue {
979    // SAFETY: `system_unbound_wq` is a C global, always available.
980    unsafe { Queue::from_raw(bindings::system_unbound_wq) }
981}
982
983/// Returns the system freezable work queue (`system_freezable_wq`).
984///
985/// It is equivalent to the one returned by [`system`] except that it's freezable.
986///
987/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
988/// items on the workqueue are drained and no new work item starts execution until thawed.
989pub fn system_freezable() -> &'static Queue {
990    // SAFETY: `system_freezable_wq` is a C global, always available.
991    unsafe { Queue::from_raw(bindings::system_freezable_wq) }
992}
993
994/// Returns the system power-efficient work queue (`system_power_efficient_wq`).
995///
996/// It is inclined towards saving power and is converted to "unbound" variants if the
997/// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
998/// returned by [`system`].
999pub fn system_power_efficient() -> &'static Queue {
1000    // SAFETY: `system_power_efficient_wq` is a C global, always available.
1001    unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
1002}
1003
1004/// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`).
1005///
1006/// It is similar to the one returned by [`system_power_efficient`] except that is freezable.
1007///
1008/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
1009/// items on the workqueue are drained and no new work item starts execution until thawed.
1010pub fn system_freezable_power_efficient() -> &'static Queue {
1011    // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available.
1012    unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) }
1013}
1014
1015/// Returns the system bottom halves work queue (`system_bh_wq`).
1016///
1017/// It is similar to the one returned by [`system`] but for work items which
1018/// need to run from a softirq context.
1019pub fn system_bh() -> &'static Queue {
1020    // SAFETY: `system_bh_wq` is a C global, always available.
1021    unsafe { Queue::from_raw(bindings::system_bh_wq) }
1022}
1023
1024/// Returns the system bottom halves high-priority work queue (`system_bh_highpri_wq`).
1025///
1026/// It is similar to the one returned by [`system_bh`] but for work items which
1027/// require higher scheduling priority.
1028pub fn system_bh_highpri() -> &'static Queue {
1029    // SAFETY: `system_bh_highpri_wq` is a C global, always available.
1030    unsafe { Queue::from_raw(bindings::system_bh_highpri_wq) }
1031}