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::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: {}", 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 //! ```
73 //!
74 //! The following example shows how multiple `work_struct` fields can be used:
75 //!
76 //! ```
77 //! use kernel::sync::Arc;
78 //! use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem};
79 //!
80 //! #[pin_data]
81 //! struct MyStruct {
82 //! value_1: i32,
83 //! value_2: i32,
84 //! #[pin]
85 //! work_1: Work<MyStruct, 1>,
86 //! #[pin]
87 //! work_2: Work<MyStruct, 2>,
88 //! }
89 //!
90 //! impl_has_work! {
91 //! impl HasWork<Self, 1> for MyStruct { self.work_1 }
92 //! impl HasWork<Self, 2> for MyStruct { self.work_2 }
93 //! }
94 //!
95 //! impl MyStruct {
96 //! fn new(value_1: i32, value_2: i32) -> Result<Arc<Self>> {
97 //! Arc::pin_init(pin_init!(MyStruct {
98 //! value_1,
99 //! value_2,
100 //! work_1 <- new_work!("MyStruct::work_1"),
101 //! work_2 <- new_work!("MyStruct::work_2"),
102 //! }), GFP_KERNEL)
103 //! }
104 //! }
105 //!
106 //! impl WorkItem<1> for MyStruct {
107 //! type Pointer = Arc<MyStruct>;
108 //!
109 //! fn run(this: Arc<MyStruct>) {
110 //! pr_info!("The value is: {}", this.value_1);
111 //! }
112 //! }
113 //!
114 //! impl WorkItem<2> for MyStruct {
115 //! type Pointer = Arc<MyStruct>;
116 //!
117 //! fn run(this: Arc<MyStruct>) {
118 //! pr_info!("The second value is: {}", this.value_2);
119 //! }
120 //! }
121 //!
122 //! fn print_1_later(val: Arc<MyStruct>) {
123 //! let _ = workqueue::system().enqueue::<Arc<MyStruct>, 1>(val);
124 //! }
125 //!
126 //! fn print_2_later(val: Arc<MyStruct>) {
127 //! let _ = workqueue::system().enqueue::<Arc<MyStruct>, 2>(val);
128 //! }
129 //! ```
130 //!
131 //! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h)
132
133 use crate::alloc::{AllocError, Flags};
134 use crate::{prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};
135 use core::marker::PhantomData;
136
137 /// Creates a [`Work`] initialiser with the given name and a newly-created lock class.
138 #[macro_export]
139 macro_rules! new_work {
140 ($($name:literal)?) => {
141 $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
142 };
143 }
144 pub use new_work;
145
146 /// A kernel work queue.
147 ///
148 /// Wraps the kernel's C `struct workqueue_struct`.
149 ///
150 /// It allows work items to be queued to run on thread pools managed by the kernel. Several are
151 /// always available, for example, `system`, `system_highpri`, `system_long`, etc.
152 #[repr(transparent)]
153 pub struct Queue(Opaque<bindings::workqueue_struct>);
154
155 // SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
156 unsafe impl Send for Queue {}
157 // SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
158 unsafe impl Sync for Queue {}
159
160 impl Queue {
161 /// Use the provided `struct workqueue_struct` with Rust.
162 ///
163 /// # Safety
164 ///
165 /// The caller must ensure that the provided raw pointer is not dangling, that it points at a
166 /// valid workqueue, and that it remains valid until the end of `'a`.
167 pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue {
168 // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The
169 // caller promises that the pointer is not dangling.
170 unsafe { &*(ptr as *const Queue) }
171 }
172
173 /// Enqueues a work item.
174 ///
175 /// This may fail if the work item is already enqueued in a workqueue.
176 ///
177 /// The work item will be submitted using `WORK_CPU_UNBOUND`.
178 pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
179 where
180 W: RawWorkItem<ID> + Send + 'static,
181 {
182 let queue_ptr = self.0.get();
183
184 // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
185 // `__enqueue` requirements are not relevant since `W` is `Send` and static.
186 //
187 // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which
188 // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this
189 // closure.
190 //
191 // Furthermore, if the C workqueue code accesses the pointer after this call to
192 // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on`
193 // will have returned true. In this case, `__enqueue` promises that the raw pointer will
194 // stay valid until we call the function pointer in the `work_struct`, so the access is ok.
195 unsafe {
196 w.__enqueue(move |work_ptr| {
197 bindings::queue_work_on(
198 bindings::wq_misc_consts_WORK_CPU_UNBOUND as _,
199 queue_ptr,
200 work_ptr,
201 )
202 })
203 }
204 }
205
206 /// Tries to spawn the given function or closure as a work item.
207 ///
208 /// This method can fail because it allocates memory to store the work item.
209 pub fn try_spawn<T: 'static + Send + FnOnce()>(
210 &self,
211 flags: Flags,
212 func: T,
213 ) -> 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, flags).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]
228 struct ClosureWork<T> {
229 #[pin]
230 work: Work<ClosureWork<T>>,
231 func: Option<T>,
232 }
233
234 impl<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
241 impl<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
271 pub 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
315 pub 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.
330 pub 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 #[pin_data]
350 #[repr(transparent)]
351 pub struct Work<T: ?Sized, const ID: u64 = 0> {
352 #[pin]
353 work: Opaque<bindings::work_struct>,
354 _inner: PhantomData<T>,
355 }
356
357 // SAFETY: Kernel work items are usable from any thread.
358 //
359 // We do not need to constrain `T` since the work item does not actually contain a `T`.
360 unsafe impl<T: ?Sized, const ID: u64> Send for Work<T, ID> {}
361 // SAFETY: Kernel work items are usable from any thread.
362 //
363 // We do not need to constrain `T` since the work item does not actually contain a `T`.
364 unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
365
366 impl<T: ?Sized, const ID: u64> Work<T, ID> {
367 /// Creates a new instance of [`Work`].
368 #[inline]
369 #[allow(clippy::new_ret_no_self)]
370 pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self>
371 where
372 T: WorkItem<ID>,
373 {
374 pin_init!(Self {
375 work <- Opaque::ffi_init(|slot| {
376 // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as
377 // the work item function.
378 unsafe {
379 bindings::init_work_with_key(
380 slot,
381 Some(T::Pointer::run),
382 false,
383 name.as_char_ptr(),
384 key.as_ptr(),
385 )
386 }
387 }),
388 _inner: PhantomData,
389 })
390 }
391
392 /// Get a pointer to the inner `work_struct`.
393 ///
394 /// # Safety
395 ///
396 /// The provided pointer must not be dangling and must be properly aligned. (But the memory
397 /// need not be initialized.)
398 #[inline]
399 pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
400 // SAFETY: The caller promises that the pointer is aligned and not dangling.
401 //
402 // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
403 // the compiler does not complain that the `work` field is unused.
404 unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) }
405 }
406 }
407
408 /// Declares that a type has a [`Work<T, ID>`] field.
409 ///
410 /// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro
411 /// like this:
412 ///
413 /// ```no_run
414 /// use kernel::workqueue::{impl_has_work, Work};
415 ///
416 /// struct MyWorkItem {
417 /// work_field: Work<MyWorkItem, 1>,
418 /// }
419 ///
420 /// impl_has_work! {
421 /// impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field }
422 /// }
423 /// ```
424 ///
425 /// Note that since the [`Work`] type is annotated with an id, you can have several `work_struct`
426 /// fields by using a different id for each one.
427 ///
428 /// # Safety
429 ///
430 /// The [`OFFSET`] constant must be the offset of a field in `Self` of type [`Work<T, ID>`]. The
431 /// methods on this trait must have exactly the behavior that the definitions given below have.
432 ///
433 /// [`impl_has_work!`]: crate::impl_has_work
434 /// [`OFFSET`]: HasWork::OFFSET
435 pub unsafe trait HasWork<T, const ID: u64 = 0> {
436 /// The offset of the [`Work<T, ID>`] field.
437 const OFFSET: usize;
438
439 /// Returns the offset of the [`Work<T, ID>`] field.
440 ///
441 /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not
442 /// [`Sized`].
443 ///
444 /// [`OFFSET`]: HasWork::OFFSET
445 #[inline]
446 fn get_work_offset(&self) -> usize {
447 Self::OFFSET
448 }
449
450 /// Returns a pointer to the [`Work<T, ID>`] field.
451 ///
452 /// # Safety
453 ///
454 /// The provided pointer must point at a valid struct of type `Self`.
455 #[inline]
456 unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID> {
457 // SAFETY: The caller promises that the pointer is valid.
458 unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work<T, ID> }
459 }
460
461 /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
462 ///
463 /// # Safety
464 ///
465 /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
466 #[inline]
467 unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self
468 where
469 Self: Sized,
470 {
471 // SAFETY: The caller promises that the pointer points at a field of the right type in the
472 // right kind of struct.
473 unsafe { (ptr as *mut u8).sub(Self::OFFSET) as *mut Self }
474 }
475 }
476
477 /// Used to safely implement the [`HasWork<T, ID>`] trait.
478 ///
479 /// # Examples
480 ///
481 /// ```
482 /// use kernel::sync::Arc;
483 /// use kernel::workqueue::{self, impl_has_work, Work};
484 ///
485 /// struct MyStruct<'a, T, const N: usize> {
486 /// work_field: Work<MyStruct<'a, T, N>, 17>,
487 /// f: fn(&'a [T; N]),
488 /// }
489 ///
490 /// impl_has_work! {
491 /// impl{'a, T, const N: usize} HasWork<MyStruct<'a, T, N>, 17>
492 /// for MyStruct<'a, T, N> { self.work_field }
493 /// }
494 /// ```
495 #[macro_export]
496 macro_rules! impl_has_work {
497 ($(impl$({$($generics:tt)*})?
498 HasWork<$work_type:ty $(, $id:tt)?>
499 for $self:ty
500 { self.$field:ident }
501 )*) => {$(
502 // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
503 // type.
504 unsafe impl$(<$($generics)+>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self {
505 const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
506
507 #[inline]
508 unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
509 // SAFETY: The caller promises that the pointer is not dangling.
510 unsafe {
511 ::core::ptr::addr_of_mut!((*ptr).$field)
512 }
513 }
514 }
515 )*};
516 }
517 pub use impl_has_work;
518
519 impl_has_work! {
520 impl{T} HasWork<Self> for ClosureWork<T> { self.work }
521 }
522
523 unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
524 where
525 T: WorkItem<ID, Pointer = Self>,
526 T: HasWork<T, ID>,
527 {
528 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
529 // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
530 let ptr = ptr as *mut Work<T, ID>;
531 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
532 let ptr = unsafe { T::work_container_of(ptr) };
533 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
534 let arc = unsafe { Arc::from_raw(ptr) };
535
536 T::run(arc)
537 }
538 }
539
540 unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>
541 where
542 T: WorkItem<ID, Pointer = Self>,
543 T: HasWork<T, ID>,
544 {
545 type EnqueueOutput = Result<(), Self>;
546
547 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
548 where
549 F: FnOnce(*mut bindings::work_struct) -> bool,
550 {
551 // Casting between const and mut is not a problem as long as the pointer is a raw pointer.
552 let ptr = Arc::into_raw(self).cast_mut();
553
554 // SAFETY: Pointers into an `Arc` point at a valid value.
555 let work_ptr = unsafe { T::raw_get_work(ptr) };
556 // SAFETY: `raw_get_work` returns a pointer to a valid value.
557 let work_ptr = unsafe { Work::raw_get(work_ptr) };
558
559 if queue_work_on(work_ptr) {
560 Ok(())
561 } else {
562 // SAFETY: The work queue has not taken ownership of the pointer.
563 Err(unsafe { Arc::from_raw(ptr) })
564 }
565 }
566 }
567
568 unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<Box<T>>
569 where
570 T: WorkItem<ID, Pointer = Self>,
571 T: HasWork<T, ID>,
572 {
573 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
574 // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
575 let ptr = ptr as *mut Work<T, ID>;
576 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
577 let ptr = unsafe { T::work_container_of(ptr) };
578 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
579 let boxed = unsafe { Box::from_raw(ptr) };
580 // SAFETY: The box was already pinned when it was enqueued.
581 let pinned = unsafe { Pin::new_unchecked(boxed) };
582
583 T::run(pinned)
584 }
585 }
586
587 unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<Box<T>>
588 where
589 T: WorkItem<ID, Pointer = Self>,
590 T: HasWork<T, ID>,
591 {
592 type EnqueueOutput = ();
593
594 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
595 where
596 F: FnOnce(*mut bindings::work_struct) -> bool,
597 {
598 // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily
599 // remove the `Pin` wrapper.
600 let boxed = unsafe { Pin::into_inner_unchecked(self) };
601 let ptr = Box::into_raw(boxed);
602
603 // SAFETY: Pointers into a `Box` point at a valid value.
604 let work_ptr = unsafe { T::raw_get_work(ptr) };
605 // SAFETY: `raw_get_work` returns a pointer to a valid value.
606 let work_ptr = unsafe { Work::raw_get(work_ptr) };
607
608 if !queue_work_on(work_ptr) {
609 // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a
610 // workqueue.
611 unsafe { ::core::hint::unreachable_unchecked() }
612 }
613 }
614 }
615
616 /// Returns the system work queue (`system_wq`).
617 ///
618 /// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
619 /// users which expect relatively short queue flush time.
620 ///
621 /// Callers shouldn't queue work items which can run for too long.
622 pub fn system() -> &'static Queue {
623 // SAFETY: `system_wq` is a C global, always available.
624 unsafe { Queue::from_raw(bindings::system_wq) }
625 }
626
627 /// Returns the system high-priority work queue (`system_highpri_wq`).
628 ///
629 /// It is similar to the one returned by [`system`] but for work items which require higher
630 /// scheduling priority.
631 pub fn system_highpri() -> &'static Queue {
632 // SAFETY: `system_highpri_wq` is a C global, always available.
633 unsafe { Queue::from_raw(bindings::system_highpri_wq) }
634 }
635
636 /// Returns the system work queue for potentially long-running work items (`system_long_wq`).
637 ///
638 /// It is similar to the one returned by [`system`] but may host long running work items. Queue
639 /// flushing might take relatively long.
640 pub fn system_long() -> &'static Queue {
641 // SAFETY: `system_long_wq` is a C global, always available.
642 unsafe { Queue::from_raw(bindings::system_long_wq) }
643 }
644
645 /// Returns the system unbound work queue (`system_unbound_wq`).
646 ///
647 /// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
648 /// are executed immediately as long as `max_active` limit is not reached and resources are
649 /// available.
650 pub fn system_unbound() -> &'static Queue {
651 // SAFETY: `system_unbound_wq` is a C global, always available.
652 unsafe { Queue::from_raw(bindings::system_unbound_wq) }
653 }
654
655 /// Returns the system freezable work queue (`system_freezable_wq`).
656 ///
657 /// It is equivalent to the one returned by [`system`] except that it's freezable.
658 ///
659 /// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
660 /// items on the workqueue are drained and no new work item starts execution until thawed.
661 pub fn system_freezable() -> &'static Queue {
662 // SAFETY: `system_freezable_wq` is a C global, always available.
663 unsafe { Queue::from_raw(bindings::system_freezable_wq) }
664 }
665
666 /// Returns the system power-efficient work queue (`system_power_efficient_wq`).
667 ///
668 /// It is inclined towards saving power and is converted to "unbound" variants if the
669 /// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
670 /// returned by [`system`].
671 pub fn system_power_efficient() -> &'static Queue {
672 // SAFETY: `system_power_efficient_wq` is a C global, always available.
673 unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
674 }
675
676 /// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`).
677 ///
678 /// It is similar to the one returned by [`system_power_efficient`] except that is freezable.
679 ///
680 /// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
681 /// items on the workqueue are drained and no new work item starts execution until thawed.
682 pub fn system_freezable_power_efficient() -> &'static Queue {
683 // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available.
684 unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) }
685 }
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