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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
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//! ## 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, impl_has_work, new_work, Work, WorkItem};
39//!
40//! #[pin_data]
41//! struct MyStruct {
42//! value: i32,
43//! #[pin]
44//! work: Work<MyStruct>,
45//! }
46//!
47//! impl_has_work! {
48//! impl HasWork<Self> for MyStruct { self.work }
49//! }
50//!
51//! impl MyStruct {
52//! fn new(value: i32) -> Result<Arc<Self>> {
53//! Arc::pin_init(pin_init!(MyStruct {
54//! value,
55//! work <- new_work!("MyStruct::work"),
56//! }))
57//! }
58//! }
59//!
60//! impl WorkItem for MyStruct {
61//! type Pointer = Arc<MyStruct>;
62//!
63//! fn run(this: Arc<MyStruct>) {
64//! pr_info!("The value is: {}", this.value);
65//! }
66//! }
67//!
68//! /// This method will enqueue the struct for execution on the system workqueue, where its value
69//! /// will be printed.
70//! fn print_later(val: Arc<MyStruct>) {
71//! let _ = workqueue::system().enqueue(val);
72//! }
73//! ```
74//!
75//! The following example shows how multiple `work_struct` fields can be used:
76//!
77//! ```
78//! use kernel::prelude::*;
79//! use kernel::sync::Arc;
80//! use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem};
81//!
82//! #[pin_data]
83//! struct MyStruct {
84//! value_1: i32,
85//! value_2: i32,
86//! #[pin]
87//! work_1: Work<MyStruct, 1>,
88//! #[pin]
89//! work_2: Work<MyStruct, 2>,
90//! }
91//!
92//! impl_has_work! {
93//! impl HasWork<Self, 1> for MyStruct { self.work_1 }
94//! impl HasWork<Self, 2> for MyStruct { self.work_2 }
95//! }
96//!
97//! impl MyStruct {
98//! fn new(value_1: i32, value_2: i32) -> Result<Arc<Self>> {
99//! Arc::pin_init(pin_init!(MyStruct {
100//! value_1,
101//! value_2,
102//! work_1 <- new_work!("MyStruct::work_1"),
103//! work_2 <- new_work!("MyStruct::work_2"),
104//! }))
105//! }
106//! }
107//!
108//! impl WorkItem<1> for MyStruct {
109//! type Pointer = Arc<MyStruct>;
110//!
111//! fn run(this: Arc<MyStruct>) {
112//! pr_info!("The value is: {}", this.value_1);
113//! }
114//! }
115//!
116//! impl WorkItem<2> for MyStruct {
117//! type Pointer = Arc<MyStruct>;
118//!
119//! fn run(this: Arc<MyStruct>) {
120//! pr_info!("The second value is: {}", this.value_2);
121//! }
122//! }
123//!
124//! fn print_1_later(val: Arc<MyStruct>) {
125//! let _ = workqueue::system().enqueue::<Arc<MyStruct>, 1>(val);
126//! }
127//!
128//! fn print_2_later(val: Arc<MyStruct>) {
129//! let _ = workqueue::system().enqueue::<Arc<MyStruct>, 2>(val);
130//! }
131//! ```
132//!
133//! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h)
134
135use crate::{bindings, prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};
136use alloc::alloc::AllocError;
137use alloc::boxed::Box;
138use core::marker::PhantomData;
139use core::pin::Pin;
140
141/// Creates a [`Work`] initialiser with the given name and a newly-created lock class.
142#[macro_export]
143macro_rules! new_work {
144 ($($name:literal)?) => {
145 $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
146 };
147}
148pub use new_work;
149
150/// A kernel work queue.
151///
152/// Wraps the kernel's C `struct workqueue_struct`.
153///
154/// It allows work items to be queued to run on thread pools managed by the kernel. Several are
155/// always available, for example, `system`, `system_highpri`, `system_long`, etc.
156#[repr(transparent)]
157pub struct Queue(Opaque<bindings::workqueue_struct>);
158
159// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
160unsafe impl Send for Queue {}
161// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
162unsafe impl Sync for Queue {}
163
164impl Queue {
165 /// Use the provided `struct workqueue_struct` with Rust.
166 ///
167 /// # Safety
168 ///
169 /// The caller must ensure that the provided raw pointer is not dangling, that it points at a
170 /// valid workqueue, and that it remains valid until the end of `'a`.
171 pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue {
172 // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The
173 // caller promises that the pointer is not dangling.
174 unsafe { &*(ptr as *const Queue) }
175 }
176
177 /// Enqueues a work item.
178 ///
179 /// This may fail if the work item is already enqueued in a workqueue.
180 ///
181 /// The work item will be submitted using `WORK_CPU_UNBOUND`.
182 pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
183 where
184 W: RawWorkItem<ID> + Send + 'static,
185 {
186 let queue_ptr = self.0.get();
187
188 // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
189 // `__enqueue` requirements are not relevant since `W` is `Send` and static.
190 //
191 // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which
192 // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this
193 // closure.
194 //
195 // Furthermore, if the C workqueue code accesses the pointer after this call to
196 // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on`
197 // will have returned true. In this case, `__enqueue` promises that the raw pointer will
198 // stay valid until we call the function pointer in the `work_struct`, so the access is ok.
199 unsafe {
200 w.__enqueue(move |work_ptr| {
201 bindings::queue_work_on(
202 bindings::wq_misc_consts_WORK_CPU_UNBOUND as _,
203 queue_ptr,
204 work_ptr,
205 )
206 })
207 }
208 }
209
210 /// Tries to spawn the given function or closure as a work item.
211 ///
212 /// This method can fail because it allocates memory to store the work item.
213 pub fn try_spawn<T: 'static + Send + FnOnce()>(&self, func: T) -> Result<(), AllocError> {
214 let init = pin_init!(ClosureWork {
215 work <- new_work!("Queue::try_spawn"),
216 func: Some(func),
217 });
218
219 self.enqueue(Box::pin_init(init).map_err(|_| AllocError)?);
220 Ok(())
221 }
222}
223
224/// A helper type used in [`try_spawn`].
225///
226/// [`try_spawn`]: Queue::try_spawn
227#[pin_data]
228struct ClosureWork<T> {
229 #[pin]
230 work: Work<ClosureWork<T>>,
231 func: Option<T>,
232}
233
234impl<T> ClosureWork<T> {
235 fn project(self: Pin<&mut Self>) -> &mut Option<T> {
236 // SAFETY: The `func` field is not structurally pinned.
237 unsafe { &mut self.get_unchecked_mut().func }
238 }
239}
240
241impl<T: FnOnce()> WorkItem for ClosureWork<T> {
242 type Pointer = Pin<Box<Self>>;
243
244 fn run(mut this: Pin<Box<Self>>) {
245 if let Some(func) = this.as_mut().project().take() {
246 (func)()
247 }
248 }
249}
250
251/// A raw work item.
252///
253/// This is the low-level trait that is designed for being as general as possible.
254///
255/// The `ID` parameter to this trait exists so that a single type can provide multiple
256/// implementations of this trait. For example, if a struct has multiple `work_struct` fields, then
257/// you will implement this trait once for each field, using a different id for each field. The
258/// actual value of the id is not important as long as you use different ids for different fields
259/// of the same struct. (Fields of different structs need not use different ids.)
260///
261/// Note that the id is used only to select the right method to call during compilation. It won't be
262/// part of the final executable.
263///
264/// # Safety
265///
266/// Implementers must ensure that any pointers passed to a `queue_work_on` closure by [`__enqueue`]
267/// remain valid for the duration specified in the guarantees section of the documentation for
268/// [`__enqueue`].
269///
270/// [`__enqueue`]: RawWorkItem::__enqueue
271pub unsafe trait RawWorkItem<const ID: u64> {
272 /// The return type of [`Queue::enqueue`].
273 type EnqueueOutput;
274
275 /// Enqueues this work item on a queue using the provided `queue_work_on` method.
276 ///
277 /// # Guarantees
278 ///
279 /// If this method calls the provided closure, then the raw pointer is guaranteed to point at a
280 /// valid `work_struct` for the duration of the call to the closure. If the closure returns
281 /// true, then it is further guaranteed that the pointer remains valid until someone calls the
282 /// function pointer stored in the `work_struct`.
283 ///
284 /// # Safety
285 ///
286 /// The provided closure may only return `false` if the `work_struct` is already in a workqueue.
287 ///
288 /// If the work item type is annotated with any lifetimes, then you must not call the function
289 /// pointer after any such lifetime expires. (Never calling the function pointer is okay.)
290 ///
291 /// If the work item type is not [`Send`], then the function pointer must be called on the same
292 /// thread as the call to `__enqueue`.
293 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
294 where
295 F: FnOnce(*mut bindings::work_struct) -> bool;
296}
297
298/// Defines the method that should be called directly when a work item is executed.
299///
300/// This trait is implemented by `Pin<Box<T>>` and [`Arc<T>`], and is mainly intended to be
301/// implemented for smart pointer types. For your own structs, you would implement [`WorkItem`]
302/// instead. The [`run`] method on this trait will usually just perform the appropriate
303/// `container_of` translation and then call into the [`run`][WorkItem::run] method from the
304/// [`WorkItem`] trait.
305///
306/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
307///
308/// # Safety
309///
310/// Implementers must ensure that [`__enqueue`] uses a `work_struct` initialized with the [`run`]
311/// method of this trait as the function pointer.
312///
313/// [`__enqueue`]: RawWorkItem::__enqueue
314/// [`run`]: WorkItemPointer::run
315pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
316 /// Run this work item.
317 ///
318 /// # Safety
319 ///
320 /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
321 /// where the `queue_work_on` closure returned true, and the pointer must still be valid.
322 ///
323 /// [`__enqueue`]: RawWorkItem::__enqueue
324 unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
325}
326
327/// Defines the method that should be called when this work item is executed.
328///
329/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
330pub trait WorkItem<const ID: u64 = 0> {
331 /// The pointer type that this struct is wrapped in. This will typically be `Arc<Self>` or
332 /// `Pin<Box<Self>>`.
333 type Pointer: WorkItemPointer<ID>;
334
335 /// The method that should be called when this work item is executed.
336 fn run(this: Self::Pointer);
337}
338
339/// Links for a work item.
340///
341/// This struct contains a function pointer to the [`run`] function from the [`WorkItemPointer`]
342/// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue.
343///
344/// Wraps the kernel's C `struct work_struct`.
345///
346/// This is a helper type used to associate a `work_struct` with the [`WorkItem`] that uses it.
347///
348/// [`run`]: WorkItemPointer::run
349#[repr(transparent)]
350pub struct Work<T: ?Sized, const ID: u64 = 0> {
351 work: Opaque<bindings::work_struct>,
352 _inner: PhantomData<T>,
353}
354
355// SAFETY: Kernel work items are usable from any thread.
356//
357// We do not need to constrain `T` since the work item does not actually contain a `T`.
358unsafe impl<T: ?Sized, const ID: u64> Send for Work<T, ID> {}
359// SAFETY: Kernel work items are usable from any thread.
360//
361// We do not need to constrain `T` since the work item does not actually contain a `T`.
362unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
363
364impl<T: ?Sized, const ID: u64> Work<T, ID> {
365 /// Creates a new instance of [`Work`].
366 #[inline]
367 #[allow(clippy::new_ret_no_self)]
368 pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self>
369 where
370 T: WorkItem<ID>,
371 {
372 // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as the work
373 // item function.
374 unsafe {
375 kernel::init::pin_init_from_closure(move |slot| {
376 let slot = Self::raw_get(slot);
377 bindings::init_work_with_key(
378 slot,
379 Some(T::Pointer::run),
380 false,
381 name.as_char_ptr(),
382 key.as_ptr(),
383 );
384 Ok(())
385 })
386 }
387 }
388
389 /// Get a pointer to the inner `work_struct`.
390 ///
391 /// # Safety
392 ///
393 /// The provided pointer must not be dangling and must be properly aligned. (But the memory
394 /// need not be initialized.)
395 #[inline]
396 pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
397 // SAFETY: The caller promises that the pointer is aligned and not dangling.
398 //
399 // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
400 // the compiler does not complain that the `work` field is unused.
401 unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) }
402 }
403}
404
405/// Declares that a type has a [`Work<T, ID>`] field.
406///
407/// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro
408/// like this:
409///
410/// ```no_run
411/// use kernel::prelude::*;
412/// use kernel::workqueue::{impl_has_work, Work};
413///
414/// struct MyWorkItem {
415/// work_field: Work<MyWorkItem, 1>,
416/// }
417///
418/// impl_has_work! {
419/// impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field }
420/// }
421/// ```
422///
423/// Note that since the [`Work`] type is annotated with an id, you can have several `work_struct`
424/// fields by using a different id for each one.
425///
426/// # Safety
427///
428/// The [`OFFSET`] constant must be the offset of a field in `Self` of type [`Work<T, ID>`]. The
429/// methods on this trait must have exactly the behavior that the definitions given below have.
430///
431/// [`impl_has_work!`]: crate::impl_has_work
432/// [`OFFSET`]: HasWork::OFFSET
433pub unsafe trait HasWork<T, const ID: u64 = 0> {
434 /// The offset of the [`Work<T, ID>`] field.
435 const OFFSET: usize;
436
437 /// Returns the offset of the [`Work<T, ID>`] field.
438 ///
439 /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not
440 /// [`Sized`].
441 ///
442 /// [`OFFSET`]: HasWork::OFFSET
443 #[inline]
444 fn get_work_offset(&self) -> usize {
445 Self::OFFSET
446 }
447
448 /// Returns a pointer to the [`Work<T, ID>`] field.
449 ///
450 /// # Safety
451 ///
452 /// The provided pointer must point at a valid struct of type `Self`.
453 #[inline]
454 unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID> {
455 // SAFETY: The caller promises that the pointer is valid.
456 unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work<T, ID> }
457 }
458
459 /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
460 ///
461 /// # Safety
462 ///
463 /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
464 #[inline]
465 unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self
466 where
467 Self: Sized,
468 {
469 // SAFETY: The caller promises that the pointer points at a field of the right type in the
470 // right kind of struct.
471 unsafe { (ptr as *mut u8).sub(Self::OFFSET) as *mut Self }
472 }
473}
474
475/// Used to safely implement the [`HasWork<T, ID>`] trait.
476///
477/// # Examples
478///
479/// ```
480/// use kernel::sync::Arc;
481/// use kernel::workqueue::{self, impl_has_work, Work};
482///
483/// struct MyStruct {
484/// work_field: Work<MyStruct, 17>,
485/// }
486///
487/// impl_has_work! {
488/// impl HasWork<MyStruct, 17> for MyStruct { self.work_field }
489/// }
490/// ```
491#[macro_export]
492macro_rules! impl_has_work {
493 ($(impl$(<$($implarg:ident),*>)?
494 HasWork<$work_type:ty $(, $id:tt)?>
495 for $self:ident $(<$($selfarg:ident),*>)?
496 { self.$field:ident }
497 )*) => {$(
498 // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
499 // type.
500 unsafe impl$(<$($implarg),*>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self $(<$($selfarg),*>)? {
501 const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
502
503 #[inline]
504 unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
505 // SAFETY: The caller promises that the pointer is not dangling.
506 unsafe {
507 ::core::ptr::addr_of_mut!((*ptr).$field)
508 }
509 }
510 }
511 )*};
512}
513pub use impl_has_work;
514
515impl_has_work! {
516 impl<T> HasWork<Self> for ClosureWork<T> { self.work }
517}
518
519unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
520where
521 T: WorkItem<ID, Pointer = Self>,
522 T: HasWork<T, ID>,
523{
524 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
525 // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
526 let ptr = ptr as *mut Work<T, ID>;
527 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
528 let ptr = unsafe { T::work_container_of(ptr) };
529 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
530 let arc = unsafe { Arc::from_raw(ptr) };
531
532 T::run(arc)
533 }
534}
535
536unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>
537where
538 T: WorkItem<ID, Pointer = Self>,
539 T: HasWork<T, ID>,
540{
541 type EnqueueOutput = Result<(), Self>;
542
543 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
544 where
545 F: FnOnce(*mut bindings::work_struct) -> bool,
546 {
547 // Casting between const and mut is not a problem as long as the pointer is a raw pointer.
548 let ptr = Arc::into_raw(self).cast_mut();
549
550 // SAFETY: Pointers into an `Arc` point at a valid value.
551 let work_ptr = unsafe { T::raw_get_work(ptr) };
552 // SAFETY: `raw_get_work` returns a pointer to a valid value.
553 let work_ptr = unsafe { Work::raw_get(work_ptr) };
554
555 if queue_work_on(work_ptr) {
556 Ok(())
557 } else {
558 // SAFETY: The work queue has not taken ownership of the pointer.
559 Err(unsafe { Arc::from_raw(ptr) })
560 }
561 }
562}
563
564unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<Box<T>>
565where
566 T: WorkItem<ID, Pointer = Self>,
567 T: HasWork<T, ID>,
568{
569 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
570 // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
571 let ptr = ptr as *mut Work<T, ID>;
572 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
573 let ptr = unsafe { T::work_container_of(ptr) };
574 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
575 let boxed = unsafe { Box::from_raw(ptr) };
576 // SAFETY: The box was already pinned when it was enqueued.
577 let pinned = unsafe { Pin::new_unchecked(boxed) };
578
579 T::run(pinned)
580 }
581}
582
583unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<Box<T>>
584where
585 T: WorkItem<ID, Pointer = Self>,
586 T: HasWork<T, ID>,
587{
588 type EnqueueOutput = ();
589
590 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
591 where
592 F: FnOnce(*mut bindings::work_struct) -> bool,
593 {
594 // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily
595 // remove the `Pin` wrapper.
596 let boxed = unsafe { Pin::into_inner_unchecked(self) };
597 let ptr = Box::into_raw(boxed);
598
599 // SAFETY: Pointers into a `Box` point at a valid value.
600 let work_ptr = unsafe { T::raw_get_work(ptr) };
601 // SAFETY: `raw_get_work` returns a pointer to a valid value.
602 let work_ptr = unsafe { Work::raw_get(work_ptr) };
603
604 if !queue_work_on(work_ptr) {
605 // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a
606 // workqueue.
607 unsafe { ::core::hint::unreachable_unchecked() }
608 }
609 }
610}
611
612/// Returns the system work queue (`system_wq`).
613///
614/// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
615/// users which expect relatively short queue flush time.
616///
617/// Callers shouldn't queue work items which can run for too long.
618pub fn system() -> &'static Queue {
619 // SAFETY: `system_wq` is a C global, always available.
620 unsafe { Queue::from_raw(bindings::system_wq) }
621}
622
623/// Returns the system high-priority work queue (`system_highpri_wq`).
624///
625/// It is similar to the one returned by [`system`] but for work items which require higher
626/// scheduling priority.
627pub fn system_highpri() -> &'static Queue {
628 // SAFETY: `system_highpri_wq` is a C global, always available.
629 unsafe { Queue::from_raw(bindings::system_highpri_wq) }
630}
631
632/// Returns the system work queue for potentially long-running work items (`system_long_wq`).
633///
634/// It is similar to the one returned by [`system`] but may host long running work items. Queue
635/// flushing might take relatively long.
636pub fn system_long() -> &'static Queue {
637 // SAFETY: `system_long_wq` is a C global, always available.
638 unsafe { Queue::from_raw(bindings::system_long_wq) }
639}
640
641/// Returns the system unbound work queue (`system_unbound_wq`).
642///
643/// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
644/// are executed immediately as long as `max_active` limit is not reached and resources are
645/// available.
646pub fn system_unbound() -> &'static Queue {
647 // SAFETY: `system_unbound_wq` is a C global, always available.
648 unsafe { Queue::from_raw(bindings::system_unbound_wq) }
649}
650
651/// Returns the system freezable work queue (`system_freezable_wq`).
652///
653/// It is equivalent to the one returned by [`system`] except that it's freezable.
654///
655/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
656/// items on the workqueue are drained and no new work item starts execution until thawed.
657pub fn system_freezable() -> &'static Queue {
658 // SAFETY: `system_freezable_wq` is a C global, always available.
659 unsafe { Queue::from_raw(bindings::system_freezable_wq) }
660}
661
662/// Returns the system power-efficient work queue (`system_power_efficient_wq`).
663///
664/// It is inclined towards saving power and is converted to "unbound" variants if the
665/// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
666/// returned by [`system`].
667pub fn system_power_efficient() -> &'static Queue {
668 // SAFETY: `system_power_efficient_wq` is a C global, always available.
669 unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
670}
671
672/// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`).
673///
674/// It is similar to the one returned by [`system_power_efficient`] except that is freezable.
675///
676/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
677/// items on the workqueue are drained and no new work item starts execution until thawed.
678pub fn system_freezable_power_efficient() -> &'static Queue {
679 // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available.
680 unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) }
681}