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: {}\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//! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h)
135
136use crate::alloc::{AllocError, Flags};
137use crate::{prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};
138use core::marker::PhantomData;
139
140/// Creates a [`Work`] initialiser with the given name and a newly-created lock class.
141#[macro_export]
142macro_rules! new_work {
143 ($($name:literal)?) => {
144 $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
145 };
146}
147pub use new_work;
148
149/// A kernel work queue.
150///
151/// Wraps the kernel's C `struct workqueue_struct`.
152///
153/// It allows work items to be queued to run on thread pools managed by the kernel. Several are
154/// always available, for example, `system`, `system_highpri`, `system_long`, etc.
155#[repr(transparent)]
156pub struct Queue(Opaque<bindings::workqueue_struct>);
157
158// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
159unsafe impl Send for Queue {}
160// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
161unsafe impl Sync for Queue {}
162
163impl Queue {
164 /// Use the provided `struct workqueue_struct` with Rust.
165 ///
166 /// # Safety
167 ///
168 /// The caller must ensure that the provided raw pointer is not dangling, that it points at a
169 /// valid workqueue, and that it remains valid until the end of `'a`.
170 pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue {
171 // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The
172 // caller promises that the pointer is not dangling.
173 unsafe { &*(ptr as *const Queue) }
174 }
175
176 /// Enqueues a work item.
177 ///
178 /// This may fail if the work item is already enqueued in a workqueue.
179 ///
180 /// The work item will be submitted using `WORK_CPU_UNBOUND`.
181 pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
182 where
183 W: RawWorkItem<ID> + Send + 'static,
184 {
185 let queue_ptr = self.0.get();
186
187 // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
188 // `__enqueue` requirements are not relevant since `W` is `Send` and static.
189 //
190 // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which
191 // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this
192 // closure.
193 //
194 // Furthermore, if the C workqueue code accesses the pointer after this call to
195 // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on`
196 // will have returned true. In this case, `__enqueue` promises that the raw pointer will
197 // stay valid until we call the function pointer in the `work_struct`, so the access is ok.
198 unsafe {
199 w.__enqueue(move |work_ptr| {
200 bindings::queue_work_on(
201 bindings::wq_misc_consts_WORK_CPU_UNBOUND as _,
202 queue_ptr,
203 work_ptr,
204 )
205 })
206 }
207 }
208
209 /// Tries to spawn the given function or closure as a work item.
210 ///
211 /// This method can fail because it allocates memory to store the work item.
212 pub fn try_spawn<T: 'static + Send + FnOnce()>(
213 &self,
214 flags: Flags,
215 func: T,
216 ) -> Result<(), AllocError> {
217 let init = pin_init!(ClosureWork {
218 work <- new_work!("Queue::try_spawn"),
219 func: Some(func),
220 });
221
222 self.enqueue(KBox::pin_init(init, flags).map_err(|_| AllocError)?);
223 Ok(())
224 }
225}
226
227/// A helper type used in [`try_spawn`].
228///
229/// [`try_spawn`]: Queue::try_spawn
230#[pin_data]
231struct ClosureWork<T> {
232 #[pin]
233 work: Work<ClosureWork<T>>,
234 func: Option<T>,
235}
236
237impl<T> ClosureWork<T> {
238 fn project(self: Pin<&mut Self>) -> &mut Option<T> {
239 // SAFETY: The `func` field is not structurally pinned.
240 unsafe { &mut self.get_unchecked_mut().func }
241 }
242}
243
244impl<T: FnOnce()> WorkItem for ClosureWork<T> {
245 type Pointer = Pin<KBox<Self>>;
246
247 fn run(mut this: Pin<KBox<Self>>) {
248 if let Some(func) = this.as_mut().project().take() {
249 (func)()
250 }
251 }
252}
253
254/// A raw work item.
255///
256/// This is the low-level trait that is designed for being as general as possible.
257///
258/// The `ID` parameter to this trait exists so that a single type can provide multiple
259/// implementations of this trait. For example, if a struct has multiple `work_struct` fields, then
260/// you will implement this trait once for each field, using a different id for each field. The
261/// actual value of the id is not important as long as you use different ids for different fields
262/// of the same struct. (Fields of different structs need not use different ids.)
263///
264/// Note that the id is used only to select the right method to call during compilation. It won't be
265/// part of the final executable.
266///
267/// # Safety
268///
269/// Implementers must ensure that any pointers passed to a `queue_work_on` closure by [`__enqueue`]
270/// remain valid for the duration specified in the guarantees section of the documentation for
271/// [`__enqueue`].
272///
273/// [`__enqueue`]: RawWorkItem::__enqueue
274pub unsafe trait RawWorkItem<const ID: u64> {
275 /// The return type of [`Queue::enqueue`].
276 type EnqueueOutput;
277
278 /// Enqueues this work item on a queue using the provided `queue_work_on` method.
279 ///
280 /// # Guarantees
281 ///
282 /// If this method calls the provided closure, then the raw pointer is guaranteed to point at a
283 /// valid `work_struct` for the duration of the call to the closure. If the closure returns
284 /// true, then it is further guaranteed that the pointer remains valid until someone calls the
285 /// function pointer stored in the `work_struct`.
286 ///
287 /// # Safety
288 ///
289 /// The provided closure may only return `false` if the `work_struct` is already in a workqueue.
290 ///
291 /// If the work item type is annotated with any lifetimes, then you must not call the function
292 /// pointer after any such lifetime expires. (Never calling the function pointer is okay.)
293 ///
294 /// If the work item type is not [`Send`], then the function pointer must be called on the same
295 /// thread as the call to `__enqueue`.
296 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
297 where
298 F: FnOnce(*mut bindings::work_struct) -> bool;
299}
300
301/// Defines the method that should be called directly when a work item is executed.
302///
303/// This trait is implemented by `Pin<KBox<T>>` and [`Arc<T>`], and is mainly intended to be
304/// implemented for smart pointer types. For your own structs, you would implement [`WorkItem`]
305/// instead. The [`run`] method on this trait will usually just perform the appropriate
306/// `container_of` translation and then call into the [`run`][WorkItem::run] method from the
307/// [`WorkItem`] trait.
308///
309/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
310///
311/// # Safety
312///
313/// Implementers must ensure that [`__enqueue`] uses a `work_struct` initialized with the [`run`]
314/// method of this trait as the function pointer.
315///
316/// [`__enqueue`]: RawWorkItem::__enqueue
317/// [`run`]: WorkItemPointer::run
318pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
319 /// Run this work item.
320 ///
321 /// # Safety
322 ///
323 /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`]
324 /// where the `queue_work_on` closure returned true, and the pointer must still be valid.
325 ///
326 /// [`__enqueue`]: RawWorkItem::__enqueue
327 unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
328}
329
330/// Defines the method that should be called when this work item is executed.
331///
332/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
333pub trait WorkItem<const ID: u64 = 0> {
334 /// The pointer type that this struct is wrapped in. This will typically be `Arc<Self>` or
335 /// `Pin<KBox<Self>>`.
336 type Pointer: WorkItemPointer<ID>;
337
338 /// The method that should be called when this work item is executed.
339 fn run(this: Self::Pointer);
340}
341
342/// Links for a work item.
343///
344/// This struct contains a function pointer to the [`run`] function from the [`WorkItemPointer`]
345/// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue.
346///
347/// Wraps the kernel's C `struct work_struct`.
348///
349/// This is a helper type used to associate a `work_struct` with the [`WorkItem`] that uses it.
350///
351/// [`run`]: WorkItemPointer::run
352#[pin_data]
353#[repr(transparent)]
354pub struct Work<T: ?Sized, const ID: u64 = 0> {
355 #[pin]
356 work: Opaque<bindings::work_struct>,
357 _inner: PhantomData<T>,
358}
359
360// SAFETY: Kernel work items are usable from any thread.
361//
362// We do not need to constrain `T` since the work item does not actually contain a `T`.
363unsafe impl<T: ?Sized, const ID: u64> Send for Work<T, ID> {}
364// SAFETY: Kernel work items are usable from any thread.
365//
366// We do not need to constrain `T` since the work item does not actually contain a `T`.
367unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
368
369impl<T: ?Sized, const ID: u64> Work<T, ID> {
370 /// Creates a new instance of [`Work`].
371 #[inline]
372 pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self>
373 where
374 T: WorkItem<ID>,
375 {
376 pin_init!(Self {
377 work <- Opaque::ffi_init(|slot| {
378 // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as
379 // the work item function.
380 unsafe {
381 bindings::init_work_with_key(
382 slot,
383 Some(T::Pointer::run),
384 false,
385 name.as_char_ptr(),
386 key.as_ptr(),
387 )
388 }
389 }),
390 _inner: PhantomData,
391 })
392 }
393
394 /// Get a pointer to the inner `work_struct`.
395 ///
396 /// # Safety
397 ///
398 /// The provided pointer must not be dangling and must be properly aligned. (But the memory
399 /// need not be initialized.)
400 #[inline]
401 pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
402 // SAFETY: The caller promises that the pointer is aligned and not dangling.
403 //
404 // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
405 // the compiler does not complain that the `work` field is unused.
406 unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) }
407 }
408}
409
410/// Declares that a type has a [`Work<T, ID>`] field.
411///
412/// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro
413/// like this:
414///
415/// ```no_run
416/// use kernel::workqueue::{impl_has_work, Work};
417///
418/// struct MyWorkItem {
419/// work_field: Work<MyWorkItem, 1>,
420/// }
421///
422/// impl_has_work! {
423/// impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field }
424/// }
425/// ```
426///
427/// Note that since the [`Work`] type is annotated with an id, you can have several `work_struct`
428/// fields by using a different id for each one.
429///
430/// # Safety
431///
432/// The methods [`raw_get_work`] and [`work_container_of`] must return valid pointers and must be
433/// true inverses of each other; that is, they must satisfy the following invariants:
434/// - `work_container_of(raw_get_work(ptr)) == ptr` for any `ptr: *mut Self`.
435/// - `raw_get_work(work_container_of(ptr)) == ptr` for any `ptr: *mut Work<T, ID>`.
436///
437/// [`impl_has_work!`]: crate::impl_has_work
438/// [`raw_get_work`]: HasWork::raw_get_work
439/// [`work_container_of`]: HasWork::work_container_of
440pub unsafe trait HasWork<T, const ID: u64 = 0> {
441 /// Returns a pointer to the [`Work<T, ID>`] field.
442 ///
443 /// # Safety
444 ///
445 /// The provided pointer must point at a valid struct of type `Self`.
446 unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID>;
447
448 /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
449 ///
450 /// # Safety
451 ///
452 /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
453 unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self;
454}
455
456/// Used to safely implement the [`HasWork<T, ID>`] trait.
457///
458/// # Examples
459///
460/// ```
461/// use kernel::sync::Arc;
462/// use kernel::workqueue::{self, impl_has_work, Work};
463///
464/// struct MyStruct<'a, T, const N: usize> {
465/// work_field: Work<MyStruct<'a, T, N>, 17>,
466/// f: fn(&'a [T; N]),
467/// }
468///
469/// impl_has_work! {
470/// impl{'a, T, const N: usize} HasWork<MyStruct<'a, T, N>, 17>
471/// for MyStruct<'a, T, N> { self.work_field }
472/// }
473/// ```
474#[macro_export]
475macro_rules! impl_has_work {
476 ($(impl$({$($generics:tt)*})?
477 HasWork<$work_type:ty $(, $id:tt)?>
478 for $self:ty
479 { self.$field:ident }
480 )*) => {$(
481 // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
482 // type.
483 unsafe impl$(<$($generics)+>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self {
484 #[inline]
485 unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
486 // SAFETY: The caller promises that the pointer is not dangling.
487 unsafe {
488 ::core::ptr::addr_of_mut!((*ptr).$field)
489 }
490 }
491
492 #[inline]
493 unsafe fn work_container_of(
494 ptr: *mut $crate::workqueue::Work<$work_type $(, $id)?>,
495 ) -> *mut Self {
496 // SAFETY: The caller promises that the pointer points at a field of the right type
497 // in the right kind of struct.
498 unsafe { $crate::container_of!(ptr, Self, $field) }
499 }
500 }
501 )*};
502}
503pub use impl_has_work;
504
505impl_has_work! {
506 impl{T} HasWork<Self> for ClosureWork<T> { self.work }
507}
508
509// SAFETY: The `__enqueue` implementation in RawWorkItem uses a `work_struct` initialized with the
510// `run` method of this trait as the function pointer because:
511// - `__enqueue` gets the `work_struct` from the `Work` field, using `T::raw_get_work`.
512// - The only safe way to create a `Work` object is through `Work::new`.
513// - `Work::new` makes sure that `T::Pointer::run` is passed to `init_work_with_key`.
514// - Finally `Work` and `RawWorkItem` guarantee that the correct `Work` field
515// will be used because of the ID const generic bound. This makes sure that `T::raw_get_work`
516// uses the correct offset for the `Work` field, and `Work::new` picks the correct
517// implementation of `WorkItemPointer` for `Arc<T>`.
518unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
519where
520 T: WorkItem<ID, Pointer = Self>,
521 T: HasWork<T, ID>,
522{
523 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
524 // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
525 let ptr = ptr as *mut Work<T, ID>;
526 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
527 let ptr = unsafe { T::work_container_of(ptr) };
528 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
529 let arc = unsafe { Arc::from_raw(ptr) };
530
531 T::run(arc)
532 }
533}
534
535// SAFETY: The `work_struct` raw pointer is guaranteed to be valid for the duration of the call to
536// the closure because we get it from an `Arc`, which means that the ref count will be at least 1,
537// and we don't drop the `Arc` ourselves. If `queue_work_on` returns true, it is further guaranteed
538// to be valid until a call to the function pointer in `work_struct` because we leak the memory it
539// points to, and only reclaim it if the closure returns false, or in `WorkItemPointer::run`, which
540// is what the function pointer in the `work_struct` must be pointing to, according to the safety
541// requirements of `WorkItemPointer`.
542unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>
543where
544 T: WorkItem<ID, Pointer = Self>,
545 T: HasWork<T, ID>,
546{
547 type EnqueueOutput = Result<(), Self>;
548
549 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
550 where
551 F: FnOnce(*mut bindings::work_struct) -> bool,
552 {
553 // Casting between const and mut is not a problem as long as the pointer is a raw pointer.
554 let ptr = Arc::into_raw(self).cast_mut();
555
556 // SAFETY: Pointers into an `Arc` point at a valid value.
557 let work_ptr = unsafe { T::raw_get_work(ptr) };
558 // SAFETY: `raw_get_work` returns a pointer to a valid value.
559 let work_ptr = unsafe { Work::raw_get(work_ptr) };
560
561 if queue_work_on(work_ptr) {
562 Ok(())
563 } else {
564 // SAFETY: The work queue has not taken ownership of the pointer.
565 Err(unsafe { Arc::from_raw(ptr) })
566 }
567 }
568}
569
570// SAFETY: TODO.
571unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<KBox<T>>
572where
573 T: WorkItem<ID, Pointer = Self>,
574 T: HasWork<T, ID>,
575{
576 unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
577 // The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
578 let ptr = ptr as *mut Work<T, ID>;
579 // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
580 let ptr = unsafe { T::work_container_of(ptr) };
581 // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
582 let boxed = unsafe { KBox::from_raw(ptr) };
583 // SAFETY: The box was already pinned when it was enqueued.
584 let pinned = unsafe { Pin::new_unchecked(boxed) };
585
586 T::run(pinned)
587 }
588}
589
590// SAFETY: TODO.
591unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<KBox<T>>
592where
593 T: WorkItem<ID, Pointer = Self>,
594 T: HasWork<T, ID>,
595{
596 type EnqueueOutput = ();
597
598 unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
599 where
600 F: FnOnce(*mut bindings::work_struct) -> bool,
601 {
602 // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily
603 // remove the `Pin` wrapper.
604 let boxed = unsafe { Pin::into_inner_unchecked(self) };
605 let ptr = KBox::into_raw(boxed);
606
607 // SAFETY: Pointers into a `KBox` point at a valid value.
608 let work_ptr = unsafe { T::raw_get_work(ptr) };
609 // SAFETY: `raw_get_work` returns a pointer to a valid value.
610 let work_ptr = unsafe { Work::raw_get(work_ptr) };
611
612 if !queue_work_on(work_ptr) {
613 // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a
614 // workqueue.
615 unsafe { ::core::hint::unreachable_unchecked() }
616 }
617 }
618}
619
620/// Returns the system work queue (`system_wq`).
621///
622/// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
623/// users which expect relatively short queue flush time.
624///
625/// Callers shouldn't queue work items which can run for too long.
626pub fn system() -> &'static Queue {
627 // SAFETY: `system_wq` is a C global, always available.
628 unsafe { Queue::from_raw(bindings::system_wq) }
629}
630
631/// Returns the system high-priority work queue (`system_highpri_wq`).
632///
633/// It is similar to the one returned by [`system`] but for work items which require higher
634/// scheduling priority.
635pub fn system_highpri() -> &'static Queue {
636 // SAFETY: `system_highpri_wq` is a C global, always available.
637 unsafe { Queue::from_raw(bindings::system_highpri_wq) }
638}
639
640/// Returns the system work queue for potentially long-running work items (`system_long_wq`).
641///
642/// It is similar to the one returned by [`system`] but may host long running work items. Queue
643/// flushing might take relatively long.
644pub fn system_long() -> &'static Queue {
645 // SAFETY: `system_long_wq` is a C global, always available.
646 unsafe { Queue::from_raw(bindings::system_long_wq) }
647}
648
649/// Returns the system unbound work queue (`system_unbound_wq`).
650///
651/// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
652/// are executed immediately as long as `max_active` limit is not reached and resources are
653/// available.
654pub fn system_unbound() -> &'static Queue {
655 // SAFETY: `system_unbound_wq` is a C global, always available.
656 unsafe { Queue::from_raw(bindings::system_unbound_wq) }
657}
658
659/// Returns the system freezable work queue (`system_freezable_wq`).
660///
661/// It is equivalent to the one returned by [`system`] except that it's freezable.
662///
663/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
664/// items on the workqueue are drained and no new work item starts execution until thawed.
665pub fn system_freezable() -> &'static Queue {
666 // SAFETY: `system_freezable_wq` is a C global, always available.
667 unsafe { Queue::from_raw(bindings::system_freezable_wq) }
668}
669
670/// Returns the system power-efficient work queue (`system_power_efficient_wq`).
671///
672/// It is inclined towards saving power and is converted to "unbound" variants if the
673/// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
674/// returned by [`system`].
675pub fn system_power_efficient() -> &'static Queue {
676 // SAFETY: `system_power_efficient_wq` is a C global, always available.
677 unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
678}
679
680/// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`).
681///
682/// It is similar to the one returned by [`system_power_efficient`] except that is freezable.
683///
684/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
685/// items on the workqueue are drained and no new work item starts execution until thawed.
686pub fn system_freezable_power_efficient() -> &'static Queue {
687 // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available.
688 unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) }
689}
690
691/// Returns the system bottom halves work queue (`system_bh_wq`).
692///
693/// It is similar to the one returned by [`system`] but for work items which
694/// need to run from a softirq context.
695pub fn system_bh() -> &'static Queue {
696 // SAFETY: `system_bh_wq` is a C global, always available.
697 unsafe { Queue::from_raw(bindings::system_bh_wq) }
698}
699
700/// Returns the system bottom halves high-priority work queue (`system_bh_highpri_wq`).
701///
702/// It is similar to the one returned by [`system_bh`] but for work items which
703/// require higher scheduling priority.
704pub fn system_bh_highpri() -> &'static Queue {
705 // SAFETY: `system_bh_highpri_wq` is a C global, always available.
706 unsafe { Queue::from_raw(bindings::system_bh_highpri_wq) }
707}
708

source code of linux/rust/kernel/workqueue.rs

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