// SPDX-License-Identifier: GPL-2.0 //! Work queues. //! //! This file has two components: The raw work item API, and the safe work item API. //! //! One pattern that is used in both APIs is the `ID` const generic, which exists to allow a single //! type to define multiple `work_struct` fields. This is done by choosing an id for each field, //! and using that id to specify which field you wish to use. (The actual value doesn't matter, as //! long as you use different values for different fields of the same struct.) Since these IDs are //! generic, they are used only at compile-time, so they shouldn't exist in the final binary. //! //! # The raw API //! //! The raw API consists of the [`RawWorkItem`] trait, where the work item needs to provide an //! arbitrary function that knows how to enqueue the work item. It should usually not be used //! directly, but if you want to, you can use it without using the pieces from the safe API. //! //! # The safe API //! //! The safe API is used via the [`Work`] struct and [`WorkItem`] traits. Furthermore, it also //! includes a trait called [`WorkItemPointer`], which is usually not used directly by the user. //! //! * The [`Work`] struct is the Rust wrapper for the C `work_struct` type. //! * The [`WorkItem`] trait is implemented for structs that can be enqueued to a workqueue. //! * The [`WorkItemPointer`] trait is implemented for the pointer type that points at a something //! that implements [`WorkItem`]. //! //! ## Example //! //! This example defines a struct that holds an integer and can be scheduled on the workqueue. When //! the struct is executed, it will print the integer. Since there is only one `work_struct` field, //! we do not need to specify ids for the fields. //! //! ``` //! use kernel::sync::Arc; //! use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem}; //! //! #[pin_data] //! struct MyStruct { //! value: i32, //! #[pin] //! work: Work, //! } //! //! impl_has_work! { //! impl HasWork for MyStruct { self.work } //! } //! //! impl MyStruct { //! fn new(value: i32) -> Result> { //! Arc::pin_init(pin_init!(MyStruct { //! value, //! work <- new_work!("MyStruct::work"), //! }), GFP_KERNEL) //! } //! } //! //! impl WorkItem for MyStruct { //! type Pointer = Arc; //! //! fn run(this: Arc) { //! pr_info!("The value is: {}", this.value); //! } //! } //! //! /// This method will enqueue the struct for execution on the system workqueue, where its value //! /// will be printed. //! fn print_later(val: Arc) { //! let _ = workqueue::system().enqueue(val); //! } //! ``` //! //! The following example shows how multiple `work_struct` fields can be used: //! //! ``` //! use kernel::sync::Arc; //! use kernel::workqueue::{self, impl_has_work, new_work, Work, WorkItem}; //! //! #[pin_data] //! struct MyStruct { //! value_1: i32, //! value_2: i32, //! #[pin] //! work_1: Work, //! #[pin] //! work_2: Work, //! } //! //! impl_has_work! { //! impl HasWork for MyStruct { self.work_1 } //! impl HasWork for MyStruct { self.work_2 } //! } //! //! impl MyStruct { //! fn new(value_1: i32, value_2: i32) -> Result> { //! Arc::pin_init(pin_init!(MyStruct { //! value_1, //! value_2, //! work_1 <- new_work!("MyStruct::work_1"), //! work_2 <- new_work!("MyStruct::work_2"), //! }), GFP_KERNEL) //! } //! } //! //! impl WorkItem<1> for MyStruct { //! type Pointer = Arc; //! //! fn run(this: Arc) { //! pr_info!("The value is: {}", this.value_1); //! } //! } //! //! impl WorkItem<2> for MyStruct { //! type Pointer = Arc; //! //! fn run(this: Arc) { //! pr_info!("The second value is: {}", this.value_2); //! } //! } //! //! fn print_1_later(val: Arc) { //! let _ = workqueue::system().enqueue::, 1>(val); //! } //! //! fn print_2_later(val: Arc) { //! let _ = workqueue::system().enqueue::, 2>(val); //! } //! ``` //! //! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h) use crate::alloc::{AllocError, Flags}; use crate::{prelude::*, sync::Arc, sync::LockClassKey, types::Opaque}; use core::marker::PhantomData; /// Creates a [`Work`] initialiser with the given name and a newly-created lock class. #[macro_export] macro_rules! new_work { ($($name:literal)?) => { $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!()) }; } pub use new_work; /// A kernel work queue. /// /// Wraps the kernel's C `struct workqueue_struct`. /// /// It allows work items to be queued to run on thread pools managed by the kernel. Several are /// always available, for example, `system`, `system_highpri`, `system_long`, etc. #[repr(transparent)] pub struct Queue(Opaque); // SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe. unsafe impl Send for Queue {} // SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe. unsafe impl Sync for Queue {} impl Queue { /// Use the provided `struct workqueue_struct` with Rust. /// /// # Safety /// /// The caller must ensure that the provided raw pointer is not dangling, that it points at a /// valid workqueue, and that it remains valid until the end of `'a`. pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue { // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The // caller promises that the pointer is not dangling. unsafe { &*(ptr as *const Queue) } } /// Enqueues a work item. /// /// This may fail if the work item is already enqueued in a workqueue. /// /// The work item will be submitted using `WORK_CPU_UNBOUND`. pub fn enqueue(&self, w: W) -> W::EnqueueOutput where W: RawWorkItem + Send + 'static, { let queue_ptr = self.0.get(); // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other // `__enqueue` requirements are not relevant since `W` is `Send` and static. // // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this // closure. // // Furthermore, if the C workqueue code accesses the pointer after this call to // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on` // will have returned true. In this case, `__enqueue` promises that the raw pointer will // stay valid until we call the function pointer in the `work_struct`, so the access is ok. unsafe { w.__enqueue(move |work_ptr| { bindings::queue_work_on( bindings::wq_misc_consts_WORK_CPU_UNBOUND as _, queue_ptr, work_ptr, ) }) } } /// Tries to spawn the given function or closure as a work item. /// /// This method can fail because it allocates memory to store the work item. pub fn try_spawn( &self, flags: Flags, func: T, ) -> Result<(), AllocError> { let init = pin_init!(ClosureWork { work <- new_work!("Queue::try_spawn"), func: Some(func), }); self.enqueue(Box::pin_init(init, flags).map_err(|_| AllocError)?); Ok(()) } } /// A helper type used in [`try_spawn`]. /// /// [`try_spawn`]: Queue::try_spawn #[pin_data] struct ClosureWork { #[pin] work: Work>, func: Option, } impl ClosureWork { fn project(self: Pin<&mut Self>) -> &mut Option { // SAFETY: The `func` field is not structurally pinned. unsafe { &mut self.get_unchecked_mut().func } } } impl WorkItem for ClosureWork { type Pointer = Pin>; fn run(mut this: Pin>) { if let Some(func) = this.as_mut().project().take() { (func)() } } } /// A raw work item. /// /// This is the low-level trait that is designed for being as general as possible. /// /// The `ID` parameter to this trait exists so that a single type can provide multiple /// implementations of this trait. For example, if a struct has multiple `work_struct` fields, then /// you will implement this trait once for each field, using a different id for each field. The /// actual value of the id is not important as long as you use different ids for different fields /// of the same struct. (Fields of different structs need not use different ids.) /// /// Note that the id is used only to select the right method to call during compilation. It won't be /// part of the final executable. /// /// # Safety /// /// Implementers must ensure that any pointers passed to a `queue_work_on` closure by [`__enqueue`] /// remain valid for the duration specified in the guarantees section of the documentation for /// [`__enqueue`]. /// /// [`__enqueue`]: RawWorkItem::__enqueue pub unsafe trait RawWorkItem { /// The return type of [`Queue::enqueue`]. type EnqueueOutput; /// Enqueues this work item on a queue using the provided `queue_work_on` method. /// /// # Guarantees /// /// If this method calls the provided closure, then the raw pointer is guaranteed to point at a /// valid `work_struct` for the duration of the call to the closure. If the closure returns /// true, then it is further guaranteed that the pointer remains valid until someone calls the /// function pointer stored in the `work_struct`. /// /// # Safety /// /// The provided closure may only return `false` if the `work_struct` is already in a workqueue. /// /// If the work item type is annotated with any lifetimes, then you must not call the function /// pointer after any such lifetime expires. (Never calling the function pointer is okay.) /// /// If the work item type is not [`Send`], then the function pointer must be called on the same /// thread as the call to `__enqueue`. unsafe fn __enqueue(self, queue_work_on: F) -> Self::EnqueueOutput where F: FnOnce(*mut bindings::work_struct) -> bool; } /// Defines the method that should be called directly when a work item is executed. /// /// This trait is implemented by `Pin>` and [`Arc`], and is mainly intended to be /// implemented for smart pointer types. For your own structs, you would implement [`WorkItem`] /// instead. The [`run`] method on this trait will usually just perform the appropriate /// `container_of` translation and then call into the [`run`][WorkItem::run] method from the /// [`WorkItem`] trait. /// /// This trait is used when the `work_struct` field is defined using the [`Work`] helper. /// /// # Safety /// /// Implementers must ensure that [`__enqueue`] uses a `work_struct` initialized with the [`run`] /// method of this trait as the function pointer. /// /// [`__enqueue`]: RawWorkItem::__enqueue /// [`run`]: WorkItemPointer::run pub unsafe trait WorkItemPointer: RawWorkItem { /// Run this work item. /// /// # Safety /// /// The provided `work_struct` pointer must originate from a previous call to [`__enqueue`] /// where the `queue_work_on` closure returned true, and the pointer must still be valid. /// /// [`__enqueue`]: RawWorkItem::__enqueue unsafe extern "C" fn run(ptr: *mut bindings::work_struct); } /// Defines the method that should be called when this work item is executed. /// /// This trait is used when the `work_struct` field is defined using the [`Work`] helper. pub trait WorkItem { /// The pointer type that this struct is wrapped in. This will typically be `Arc` or /// `Pin>`. type Pointer: WorkItemPointer; /// The method that should be called when this work item is executed. fn run(this: Self::Pointer); } /// Links for a work item. /// /// This struct contains a function pointer to the [`run`] function from the [`WorkItemPointer`] /// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue. /// /// Wraps the kernel's C `struct work_struct`. /// /// This is a helper type used to associate a `work_struct` with the [`WorkItem`] that uses it. /// /// [`run`]: WorkItemPointer::run #[pin_data] #[repr(transparent)] pub struct Work { #[pin] work: Opaque, _inner: PhantomData, } // SAFETY: Kernel work items are usable from any thread. // // We do not need to constrain `T` since the work item does not actually contain a `T`. unsafe impl Send for Work {} // SAFETY: Kernel work items are usable from any thread. // // We do not need to constrain `T` since the work item does not actually contain a `T`. unsafe impl Sync for Work {} impl Work { /// Creates a new instance of [`Work`]. #[inline] #[allow(clippy::new_ret_no_self)] pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit where T: WorkItem, { pin_init!(Self { work <- Opaque::ffi_init(|slot| { // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as // the work item function. unsafe { bindings::init_work_with_key( slot, Some(T::Pointer::run), false, name.as_char_ptr(), key.as_ptr(), ) } }), _inner: PhantomData, }) } /// Get a pointer to the inner `work_struct`. /// /// # Safety /// /// The provided pointer must not be dangling and must be properly aligned. (But the memory /// need not be initialized.) #[inline] pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct { // SAFETY: The caller promises that the pointer is aligned and not dangling. // // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that // the compiler does not complain that the `work` field is unused. unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) } } } /// Declares that a type has a [`Work`] field. /// /// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro /// like this: /// /// ```no_run /// use kernel::workqueue::{impl_has_work, Work}; /// /// struct MyWorkItem { /// work_field: Work, /// } /// /// impl_has_work! { /// impl HasWork for MyWorkItem { self.work_field } /// } /// ``` /// /// Note that since the [`Work`] type is annotated with an id, you can have several `work_struct` /// fields by using a different id for each one. /// /// # Safety /// /// The [`OFFSET`] constant must be the offset of a field in `Self` of type [`Work`]. The /// methods on this trait must have exactly the behavior that the definitions given below have. /// /// [`impl_has_work!`]: crate::impl_has_work /// [`OFFSET`]: HasWork::OFFSET pub unsafe trait HasWork { /// The offset of the [`Work`] field. const OFFSET: usize; /// Returns the offset of the [`Work`] field. /// /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not /// [`Sized`]. /// /// [`OFFSET`]: HasWork::OFFSET #[inline] fn get_work_offset(&self) -> usize { Self::OFFSET } /// Returns a pointer to the [`Work`] field. /// /// # Safety /// /// The provided pointer must point at a valid struct of type `Self`. #[inline] unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work { // SAFETY: The caller promises that the pointer is valid. unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work } } /// Returns a pointer to the struct containing the [`Work`] field. /// /// # Safety /// /// The pointer must point at a [`Work`] field in a struct of type `Self`. #[inline] unsafe fn work_container_of(ptr: *mut Work) -> *mut Self where Self: Sized, { // SAFETY: The caller promises that the pointer points at a field of the right type in the // right kind of struct. unsafe { (ptr as *mut u8).sub(Self::OFFSET) as *mut Self } } } /// Used to safely implement the [`HasWork`] trait. /// /// # Examples /// /// ``` /// use kernel::sync::Arc; /// use kernel::workqueue::{self, impl_has_work, Work}; /// /// struct MyStruct<'a, T, const N: usize> { /// work_field: Work, 17>, /// f: fn(&'a [T; N]), /// } /// /// impl_has_work! { /// impl{'a, T, const N: usize} HasWork, 17> /// for MyStruct<'a, T, N> { self.work_field } /// } /// ``` #[macro_export] macro_rules! impl_has_work { ($(impl$({$($generics:tt)*})? HasWork<$work_type:ty $(, $id:tt)?> for $self:ty { self.$field:ident } )*) => {$( // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right // type. unsafe impl$(<$($generics)+>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self { const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize; #[inline] unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> { // SAFETY: The caller promises that the pointer is not dangling. unsafe { ::core::ptr::addr_of_mut!((*ptr).$field) } } } )*}; } pub use impl_has_work; impl_has_work! { impl{T} HasWork for ClosureWork { self.work } } unsafe impl WorkItemPointer for Arc where T: WorkItem, T: HasWork, { unsafe extern "C" fn run(ptr: *mut bindings::work_struct) { // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work`. let ptr = ptr as *mut Work; // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`. let ptr = unsafe { T::work_container_of(ptr) }; // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership. let arc = unsafe { Arc::from_raw(ptr) }; T::run(arc) } } unsafe impl RawWorkItem for Arc where T: WorkItem, T: HasWork, { type EnqueueOutput = Result<(), Self>; unsafe fn __enqueue(self, queue_work_on: F) -> Self::EnqueueOutput where F: FnOnce(*mut bindings::work_struct) -> bool, { // Casting between const and mut is not a problem as long as the pointer is a raw pointer. let ptr = Arc::into_raw(self).cast_mut(); // SAFETY: Pointers into an `Arc` point at a valid value. let work_ptr = unsafe { T::raw_get_work(ptr) }; // SAFETY: `raw_get_work` returns a pointer to a valid value. let work_ptr = unsafe { Work::raw_get(work_ptr) }; if queue_work_on(work_ptr) { Ok(()) } else { // SAFETY: The work queue has not taken ownership of the pointer. Err(unsafe { Arc::from_raw(ptr) }) } } } unsafe impl WorkItemPointer for Pin> where T: WorkItem, T: HasWork, { unsafe extern "C" fn run(ptr: *mut bindings::work_struct) { // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work`. let ptr = ptr as *mut Work; // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`. let ptr = unsafe { T::work_container_of(ptr) }; // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership. let boxed = unsafe { Box::from_raw(ptr) }; // SAFETY: The box was already pinned when it was enqueued. let pinned = unsafe { Pin::new_unchecked(boxed) }; T::run(pinned) } } unsafe impl RawWorkItem for Pin> where T: WorkItem, T: HasWork, { type EnqueueOutput = (); unsafe fn __enqueue(self, queue_work_on: F) -> Self::EnqueueOutput where F: FnOnce(*mut bindings::work_struct) -> bool, { // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily // remove the `Pin` wrapper. let boxed = unsafe { Pin::into_inner_unchecked(self) }; let ptr = Box::into_raw(boxed); // SAFETY: Pointers into a `Box` point at a valid value. let work_ptr = unsafe { T::raw_get_work(ptr) }; // SAFETY: `raw_get_work` returns a pointer to a valid value. let work_ptr = unsafe { Work::raw_get(work_ptr) }; if !queue_work_on(work_ptr) { // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a // workqueue. unsafe { ::core::hint::unreachable_unchecked() } } } } /// Returns the system work queue (`system_wq`). /// /// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are /// users which expect relatively short queue flush time. /// /// Callers shouldn't queue work items which can run for too long. pub fn system() -> &'static Queue { // SAFETY: `system_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_wq) } } /// Returns the system high-priority work queue (`system_highpri_wq`). /// /// It is similar to the one returned by [`system`] but for work items which require higher /// scheduling priority. pub fn system_highpri() -> &'static Queue { // SAFETY: `system_highpri_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_highpri_wq) } } /// Returns the system work queue for potentially long-running work items (`system_long_wq`). /// /// It is similar to the one returned by [`system`] but may host long running work items. Queue /// flushing might take relatively long. pub fn system_long() -> &'static Queue { // SAFETY: `system_long_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_long_wq) } } /// Returns the system unbound work queue (`system_unbound_wq`). /// /// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items /// are executed immediately as long as `max_active` limit is not reached and resources are /// available. pub fn system_unbound() -> &'static Queue { // SAFETY: `system_unbound_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_unbound_wq) } } /// Returns the system freezable work queue (`system_freezable_wq`). /// /// It is equivalent to the one returned by [`system`] except that it's freezable. /// /// A freezable workqueue participates in the freeze phase of the system suspend operations. Work /// items on the workqueue are drained and no new work item starts execution until thawed. pub fn system_freezable() -> &'static Queue { // SAFETY: `system_freezable_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_freezable_wq) } } /// Returns the system power-efficient work queue (`system_power_efficient_wq`). /// /// It is inclined towards saving power and is converted to "unbound" variants if the /// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one /// returned by [`system`]. pub fn system_power_efficient() -> &'static Queue { // SAFETY: `system_power_efficient_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_power_efficient_wq) } } /// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`). /// /// It is similar to the one returned by [`system_power_efficient`] except that is freezable. /// /// A freezable workqueue participates in the freeze phase of the system suspend operations. Work /// items on the workqueue are drained and no new work item starts execution until thawed. pub fn system_freezable_power_efficient() -> &'static Queue { // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available. unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) } }