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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 includes
22//! 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//! ## Example
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::prelude::*;
37//! use kernel::sync::Arc;
38//! use kernel::workqueue::{self, Work, WorkItem};
39//! use kernel::{impl_has_work, new_work};
40//!
41//! #[pin_data]
42//! struct MyStruct {
43//! value: i32,
44//! #[pin]
45//! work: Work<MyStruct>,
46//! }
47//!
48//! impl_has_work! {
49//! impl HasWork<Self> for MyStruct { self.work }
50//! }
51//!
52//! impl MyStruct {
53//! fn new(value: i32) -> Result<Arc<Self>> {
54//! Arc::pin_init(pin_init!(MyStruct {
55//! value,
56//! work <- new_work!("MyStruct::work"),
57//! }))
58//! }
59//! }
60//!
61//! impl WorkItem for MyStruct {
62//! type Pointer = Arc<MyStruct>;
63//!
64//! fn run(this: Arc<MyStruct>) {
65//! pr_info!("The value is: {}", this.value);
66//! }
67//! }
68//!
69//! /// This method will enqueue the struct for execution on the system workqueue, where its value
70//! /// will be printed.
71//! fn print_later(val: Arc<MyStruct>) {
72//! let _ = workqueue::system().enqueue(val);
73//! }
74//! ```
75//!
76//! The following example shows how multiple `work_struct` fields can be used:
77//!
78//! ```
79//! use kernel::prelude::*;
80//! use kernel::sync::Arc;
81//! use kernel::workqueue::{self, Work, WorkItem};
82//! use kernel::{impl_has_work, new_work};
83//!
84//! #[pin_data]
85//! struct MyStruct {
86//! value_1: i32,
87//! value_2: i32,
88//! #[pin]
89//! work_1: Work<MyStruct, 1>,
90//! #[pin]
91//! work_2: Work<MyStruct, 2>,
92//! }
93//!
94//! impl_has_work! {
95//! impl HasWork<Self, 1> for MyStruct { self.work_1 }
96//! impl HasWork<Self, 2> for MyStruct { self.work_2 }
97//! }
98//!
99//! impl MyStruct {
100//! fn new(value_1: i32, value_2: i32) -> Result<Arc<Self>> {
101//! Arc::pin_init(pin_init!(MyStruct {
102//! value_1,
103//! value_2,
104//! work_1 <- new_work!("MyStruct::work_1"),
105//! work_2 <- new_work!("MyStruct::work_2"),
106//! }))
107//! }
108//! }
109//!
110//! impl WorkItem<1> for MyStruct {
111//! type Pointer = Arc<MyStruct>;
112//!
113//! fn run(this: Arc<MyStruct>) {
114//! pr_info!("The value is: {}", this.value_1);
115//! }
116//! }
117//!
118//! impl WorkItem<2> for MyStruct {
119//! type Pointer = Arc<MyStruct>;
120//!
121//! fn run(this: Arc<MyStruct>) {
122//! pr_info!("The second value is: {}", this.value_2);
123//! }
124//! }
125//!
126//! fn print_1_later(val: Arc<MyStruct>) {
127//! let _ = workqueue::system().enqueue::<Arc<MyStruct>, 1>(val);
128//! }
129//!
130//! fn print_2_later(val: Arc<MyStruct>) {
131//! let _ = workqueue::system().enqueue::<Arc<MyStruct>, 2>(val);
132//! }
133//! ```
134//!
135//! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h)
136
137use crate::{bindings, prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};
138use alloc::alloc::AllocError;
139use alloc::boxed::Box;
140use core::marker::PhantomData;
141use core::pin::Pin;
142
143/// Creates a [`Work`] initialiser with the given name and a newly-created lock class.
144#[macro_export]
145macro_rules! new_work {
146 ($($name:literal)?) => {
147 $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
148 };
149}
150
151/// A kernel work queue.
152///
153/// Wraps the kernel's C `struct workqueue_struct`.
154///
155/// It allows work items to be queued to run on thread pools managed by the kernel. Several are
156/// always available, for example, `system`, `system_highpri`, `system_long`, etc.
157#[repr(transparent)]
158pub struct Queue(Opaque<bindings::workqueue_struct>);
159
160// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
161unsafe impl Send for Queue {}
162// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
163unsafe impl Sync for Queue {}
164
165impl Queue {
166 /// Use the provided `struct workqueue_struct` with Rust.
167 ///
168 /// # Safety
169 ///
170 /// The caller must ensure that the provided raw pointer is not dangling, that it points at a
171 /// valid workqueue, and that it remains valid until the end of 'a.
172 pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue {
173 // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The
174 // caller promises that the pointer is not dangling.
175 unsafe { &*(ptr as *const Queue) }
176 }
177
178 /// Enqueues a work item.
179 ///
180 /// This may fail if the work item is already enqueued in a workqueue.
181 ///
182 /// The work item will be submitted using `WORK_CPU_UNBOUND`.
183 pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
184 where
185 W: RawWorkItem<ID> + Send + 'static,
186 {
187 let queue_ptr = self.0.get();
188
189 // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
190 // `__enqueue` requirements are not relevant since `W` is `Send` and static.
191 //
192 // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which
193 // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this
194 // closure.
195 //
196 // Furthermore, if the C workqueue code accesses the pointer after this call to
197 // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on`
198 // will have returned true. In this case, `__enqueue` promises that the raw pointer will
199 // stay valid until we call the function pointer in the `work_struct`, so the access is ok.
200 unsafe {
201 w.__enqueue(move |work_ptr| {
202 bindings::queue_work_on(bindings::WORK_CPU_UNBOUND as _, queue_ptr, work_ptr)
203 })
204 }
205 }
206
207 /// Tries to spawn the given function or closure as a work item.
208 ///
209 /// This method can fail because it allocates memory to store the work item.
210 pub fn try_spawn<T: 'static + Send + FnOnce()>(&self, func: T) -> Result<(), AllocError> {
211 let init = pin_init!(ClosureWork {
212 work <- new_work!("Queue::try_spawn"),
213 func: Some(func),
214 });
215
216 self.enqueue(Box::pin_init(init).map_err(|_| AllocError)?);
217 Ok(())
218 }
219}
220
221/// A helper type used in `try_spawn`.
222#[pin_data]
223struct ClosureWork<T> {
224 #[pin]
225 work: Work<ClosureWork<T>>,
226 func: Option<T>,
227}
228
229impl<T> ClosureWork<T> {
230 fn project(self: Pin<&mut Self>) -> &mut Option<T> {
231 // SAFETY: The `func` field is not structurally pinned.
232 unsafe { &mut self.get_unchecked_mut().func }
233 }
234}
235
236impl<T: FnOnce()> WorkItem for ClosureWork<T> {
237 type Pointer = Pin<Box<Self>>;
238
239 fn run(mut this: Pin<Box<Self>>) {
240 if let Some(func) = this.as_mut().project().take() {
241 (func)()
242 }
243 }
244}
245
246/// A raw work item.
247///
248/// This is the low-level trait that is designed for being as general as possible.
249///
250/// The `ID` parameter to this trait exists so that a single type can provide multiple
251/// implementations of this trait. For example, if a struct has multiple `work_struct` fields, then
252/// you will implement this trait once for each field, using a different id for each field. The
253/// actual value of the id is not important as long as you use different ids for different fields
254/// of the same struct. (Fields of different structs need not use different ids.)
255///
256/// Note that the id is used only to select the right method to call during compilation. It wont be
257/// part of the final executable.
258///
259/// # Safety
260///
261/// Implementers must ensure that any pointers passed to a `queue_work_on` closure by `__enqueue`
262/// remain valid for the duration specified in the guarantees section of the documentation for
263/// `__enqueue`.
264pub unsafe trait RawWorkItem<const ID: u64> {
265 /// The return type of [`Queue::enqueue`].
266 type EnqueueOutput;
267
268 /// Enqueues this work item on a queue using the provided `queue_work_on` method.
269 ///
270 /// # Guarantees
271 ///
272 /// If this method calls the provided closure, then the raw pointer is guaranteed to point at a
273 /// valid `work_struct` for the duration of the call to the closure. If the closure returns
274 /// true, then it is further guaranteed that the pointer remains valid until someone calls the
275 /// function pointer stored in the `work_struct`.
276 ///
277 /// # Safety
278 ///
279 /// The provided closure may only return `false` if the `work_struct` is already in a workqueue.
280 ///
281 /// If the work item type is annotated with any lifetimes, then you must not call the function
282 /// pointer after any such lifetime expires. (Never calling the function pointer is okay.)
283 ///
284 /// If the work item type is not [`Send`], then the function pointer must be called on the same
285 /// thread as the call to `__enqueue`.
286 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
287 where
288 F: FnOnce(*mut bindings::work_struct) -> bool;
289}
290
291/// Defines the method that should be called directly when a work item is executed.
292///
293/// This trait is implemented by `Pin<Box<T>>` and `Arc<T>`, and is mainly intended to be
294/// implemented for smart pointer types. For your own structs, you would implement [`WorkItem`]
295/// instead. The `run` method on this trait will usually just perform the appropriate
296/// `container_of` translation and then call into the `run` method from the [`WorkItem`] trait.
297///
298/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
299///
300/// # Safety
301///
302/// Implementers must ensure that [`__enqueue`] uses a `work_struct` initialized with the [`run`]
303/// method of this trait as the function pointer.
304///
305/// [`__enqueue`]: RawWorkItem::__enqueue
306/// [`run`]: WorkItemPointer::run
307pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
308 /// Run this work item.
309 ///
310 /// # Safety
311 ///
312 /// The provided `work_struct` pointer must originate from a previous call to `__enqueue` where
313 /// the `queue_work_on` closure returned true, and the pointer must still be valid.
314 unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
315}
316
317/// Defines the method that should be called when this work item is executed.
318///
319/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
320pub trait WorkItem<const ID: u64 = 0> {
321 /// The pointer type that this struct is wrapped in. This will typically be `Arc<Self>` or
322 /// `Pin<Box<Self>>`.
323 type Pointer: WorkItemPointer<ID>;
324
325 /// The method that should be called when this work item is executed.
326 fn run(this: Self::Pointer);
327}
328
329/// Links for a work item.
330///
331/// This struct contains a function pointer to the `run` function from the [`WorkItemPointer`]
332/// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue.
333///
334/// Wraps the kernel's C `struct work_struct`.
335///
336/// This is a helper type used to associate a `work_struct` with the [`WorkItem`] that uses it.
337#[repr(transparent)]
338pub struct Work<T: ?Sized, const ID: u64 = 0> {
339 work: Opaque<bindings::work_struct>,
340 _inner: PhantomData<T>,
341}
342
343// SAFETY: Kernel work items are usable from any thread.
344//
345// We do not need to constrain `T` since the work item does not actually contain a `T`.
346unsafe impl<T: ?Sized, const ID: u64> Send for Work<T, ID> {}
347// SAFETY: Kernel work items are usable from any thread.
348//
349// We do not need to constrain `T` since the work item does not actually contain a `T`.
350unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
351
352impl<T: ?Sized, const ID: u64> Work<T, ID> {
353 /// Creates a new instance of [`Work`].
354 #[inline]
355 #[allow(clippy::new_ret_no_self)]
356 pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self>
357 where
358 T: WorkItem<ID>,
359 {
360 // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as the work
361 // item function.
362 unsafe {
363 kernel::init::pin_init_from_closure(move |slot| {
364 let slot = Self::raw_get(slot);
365 bindings::init_work_with_key(
366 slot,
367 Some(T::Pointer::run),
368 false,
369 name.as_char_ptr(),
370 key.as_ptr(),
371 );
372 Ok(())
373 })
374 }
375 }
376
377 /// Get a pointer to the inner `work_struct`.
378 ///
379 /// # Safety
380 ///
381 /// The provided pointer must not be dangling and must be properly aligned. (But the memory
382 /// need not be initialized.)
383 #[inline]
384 pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
385 // SAFETY: The caller promises that the pointer is aligned and not dangling.
386 //
387 // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
388 // the compiler does not complain that the `work` field is unused.
389 unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) }
390 }
391}
392
393/// Declares that a type has a [`Work<T, ID>`] field.
394///
395/// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro
396/// like this:
397///
398/// ```no_run
399/// use kernel::impl_has_work;
400/// use kernel::prelude::*;
401/// use kernel::workqueue::Work;
402///
403/// struct MyWorkItem {
404/// work_field: Work<MyWorkItem, 1>,
405/// }
406///
407/// impl_has_work! {
408/// impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field }
409/// }
410/// ```
411///
412/// Note that since the `Work` type is annotated with an id, you can have several `work_struct`
413/// fields by using a different id for each one.
414///
415/// # Safety
416///
417/// The [`OFFSET`] constant must be the offset of a field in Self of type [`Work<T, ID>`]. The methods on
418/// this trait must have exactly the behavior that the definitions given below have.
419///
420/// [`Work<T, ID>`]: Work
421/// [`impl_has_work!`]: crate::impl_has_work
422/// [`OFFSET`]: HasWork::OFFSET
423pub unsafe trait HasWork<T, const ID: u64 = 0> {
424 /// The offset of the [`Work<T, ID>`] field.
425 ///
426 /// [`Work<T, ID>`]: Work
427 const OFFSET: usize;
428
429 /// Returns the offset of the [`Work<T, ID>`] field.
430 ///
431 /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not Sized.
432 ///
433 /// [`Work<T, ID>`]: Work
434 /// [`OFFSET`]: HasWork::OFFSET
435 #[inline]
436 fn get_work_offset(&self) -> usize {
437 Self::OFFSET
438 }
439
440 /// Returns a pointer to the [`Work<T, ID>`] field.
441 ///
442 /// # Safety
443 ///
444 /// The provided pointer must point at a valid struct of type `Self`.
445 ///
446 /// [`Work<T, ID>`]: Work
447 #[inline]
448 unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID> {
449 // SAFETY: The caller promises that the pointer is valid.
450 unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work<T, ID> }
451 }
452
453 /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
454 ///
455 /// # Safety
456 ///
457 /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
458 ///
459 /// [`Work<T, ID>`]: Work
460 #[inline]
461 unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self
462 where
463 Self: Sized,
464 {
465 // SAFETY: The caller promises that the pointer points at a field of the right type in the
466 // right kind of struct.
467 unsafe { (ptr as *mut u8).sub(Self::OFFSET) as *mut Self }
468 }
469}
470
471/// Used to safely implement the [`HasWork<T, ID>`] trait.
472///
473/// # Examples
474///
475/// ```
476/// use kernel::impl_has_work;
477/// use kernel::sync::Arc;
478/// use kernel::workqueue::{self, Work};
479///
480/// struct MyStruct {
481/// work_field: Work<MyStruct, 17>,
482/// }
483///
484/// impl_has_work! {
485/// impl HasWork<MyStruct, 17> for MyStruct { self.work_field }
486/// }
487/// ```
488///
489/// [`HasWork<T, ID>`]: HasWork
490#[macro_export]
491macro_rules! impl_has_work {
492 ($(impl$(<$($implarg:ident),*>)?
493 HasWork<$work_type:ty $(, $id:tt)?>
494 for $self:ident $(<$($selfarg:ident),*>)?
495 { self.$field:ident }
496 )*) => {$(
497 // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
498 // type.
499 unsafe impl$(<$($implarg),*>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self $(<$($selfarg),*>)? {
500 const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
501
502 #[inline]
503 unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
504 // SAFETY: The caller promises that the pointer is not dangling.
505 unsafe {
506 ::core::ptr::addr_of_mut!((*ptr).$field)
507 }
508 }
509 }
510 )*};
511}
512
513impl_has_work! {
514 impl<T> HasWork<Self> for ClosureWork<T> { self.work }
515}
516
517unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
518where
519 T: WorkItem<ID, Pointer = Self>,
520 T: HasWork<T, ID>,
521{
522 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
523 // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
524 let ptr = ptr as *mut Work<T, ID>;
525 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
526 let ptr = unsafe { T::work_container_of(ptr) };
527 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
528 let arc = unsafe { Arc::from_raw(ptr) };
529
530 T::run(arc)
531 }
532}
533
534unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>
535where
536 T: WorkItem<ID, Pointer = Self>,
537 T: HasWork<T, ID>,
538{
539 type EnqueueOutput = Result<(), Self>;
540
541 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
542 where
543 F: FnOnce(*mut bindings::work_struct) -> bool,
544 {
545 // Casting between const and mut is not a problem as long as the pointer is a raw pointer.
546 let ptr = Arc::into_raw(self).cast_mut();
547
548 // SAFETY: Pointers into an `Arc` point at a valid value.
549 let work_ptr = unsafe { T::raw_get_work(ptr) };
550 // SAFETY: `raw_get_work` returns a pointer to a valid value.
551 let work_ptr = unsafe { Work::raw_get(work_ptr) };
552
553 if queue_work_on(work_ptr) {
554 Ok(())
555 } else {
556 // SAFETY: The work queue has not taken ownership of the pointer.
557 Err(unsafe { Arc::from_raw(ptr) })
558 }
559 }
560}
561
562unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<Box<T>>
563where
564 T: WorkItem<ID, Pointer = Self>,
565 T: HasWork<T, ID>,
566{
567 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
568 // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
569 let ptr = ptr as *mut Work<T, ID>;
570 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
571 let ptr = unsafe { T::work_container_of(ptr) };
572 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
573 let boxed = unsafe { Box::from_raw(ptr) };
574 // SAFETY: The box was already pinned when it was enqueued.
575 let pinned = unsafe { Pin::new_unchecked(boxed) };
576
577 T::run(pinned)
578 }
579}
580
581unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<Box<T>>
582where
583 T: WorkItem<ID, Pointer = Self>,
584 T: HasWork<T, ID>,
585{
586 type EnqueueOutput = ();
587
588 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
589 where
590 F: FnOnce(*mut bindings::work_struct) -> bool,
591 {
592 // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily
593 // remove the `Pin` wrapper.
594 let boxed = unsafe { Pin::into_inner_unchecked(self) };
595 let ptr = Box::into_raw(boxed);
596
597 // SAFETY: Pointers into a `Box` point at a valid value.
598 let work_ptr = unsafe { T::raw_get_work(ptr) };
599 // SAFETY: `raw_get_work` returns a pointer to a valid value.
600 let work_ptr = unsafe { Work::raw_get(work_ptr) };
601
602 if !queue_work_on(work_ptr) {
603 // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a
604 // workqueue.
605 unsafe { ::core::hint::unreachable_unchecked() }
606 }
607 }
608}
609
610/// Returns the system work queue (`system_wq`).
611///
612/// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
613/// users which expect relatively short queue flush time.
614///
615/// Callers shouldn't queue work items which can run for too long.
616pub fn system() -> &'static Queue {
617 // SAFETY: `system_wq` is a C global, always available.
618 unsafe { Queue::from_raw(bindings::system_wq) }
619}
620
621/// Returns the system high-priority work queue (`system_highpri_wq`).
622///
623/// It is similar to the one returned by [`system`] but for work items which require higher
624/// scheduling priority.
625pub fn system_highpri() -> &'static Queue {
626 // SAFETY: `system_highpri_wq` is a C global, always available.
627 unsafe { Queue::from_raw(bindings::system_highpri_wq) }
628}
629
630/// Returns the system work queue for potentially long-running work items (`system_long_wq`).
631///
632/// It is similar to the one returned by [`system`] but may host long running work items. Queue
633/// flushing might take relatively long.
634pub fn system_long() -> &'static Queue {
635 // SAFETY: `system_long_wq` is a C global, always available.
636 unsafe { Queue::from_raw(bindings::system_long_wq) }
637}
638
639/// Returns the system unbound work queue (`system_unbound_wq`).
640///
641/// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
642/// are executed immediately as long as `max_active` limit is not reached and resources are
643/// available.
644pub fn system_unbound() -> &'static Queue {
645 // SAFETY: `system_unbound_wq` is a C global, always available.
646 unsafe { Queue::from_raw(bindings::system_unbound_wq) }
647}
648
649/// Returns the system freezable work queue (`system_freezable_wq`).
650///
651/// It is equivalent to the one returned by [`system`] except that it's freezable.
652///
653/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
654/// items on the workqueue are drained and no new work item starts execution until thawed.
655pub fn system_freezable() -> &'static Queue {
656 // SAFETY: `system_freezable_wq` is a C global, always available.
657 unsafe { Queue::from_raw(bindings::system_freezable_wq) }
658}
659
660/// Returns the system power-efficient work queue (`system_power_efficient_wq`).
661///
662/// It is inclined towards saving power and is converted to "unbound" variants if the
663/// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
664/// returned by [`system`].
665pub fn system_power_efficient() -> &'static Queue {
666 // SAFETY: `system_power_efficient_wq` is a C global, always available.
667 unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
668}
669
670/// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`).
671///
672/// It is similar to the one returned by [`system_power_efficient`] except that is freezable.
673///
674/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
675/// items on the workqueue are drained and no new work item starts execution until thawed.
676pub fn system_freezable_power_efficient() -> &'static Queue {
677 // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available.
678 unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) }
679}