embassy_executor/
lib.rs

1#![cfg_attr(not(any(feature = "arch-std", feature = "arch-wasm")), no_std)]
2#![allow(clippy::new_without_default)]
3#![doc = include_str!("../README.md")]
4#![warn(missing_docs)]
5
6//! ## Feature flags
7#![doc = document_features::document_features!(feature_label = r#"<span class="stab portability"><code>{feature}</code></span>"#)]
8
9// This mod MUST go first, so that the others see its macros.
10pub(crate) mod fmt;
11
12pub use embassy_executor_macros::task;
13
14macro_rules! check_at_most_one {
15    (@amo [$($feats:literal)*] [] [$($res:tt)*]) => {
16        #[cfg(any($($res)*))]
17        compile_error!(concat!("At most one of these features can be enabled at the same time:", $(" `", $feats, "`",)*));
18    };
19    (@amo $feats:tt [$curr:literal $($rest:literal)*] [$($res:tt)*]) => {
20        check_at_most_one!(@amo $feats [$($rest)*] [$($res)* $(all(feature=$curr, feature=$rest),)*]);
21    };
22    ($($f:literal),*$(,)?) => {
23        check_at_most_one!(@amo [$($f)*] [$($f)*] []);
24    };
25}
26check_at_most_one!(
27    "arch-avr",
28    "arch-cortex-m",
29    "arch-riscv32",
30    "arch-std",
31    "arch-wasm",
32    "arch-spin",
33);
34
35#[cfg(feature = "_arch")]
36#[cfg_attr(feature = "arch-avr", path = "arch/avr.rs")]
37#[cfg_attr(feature = "arch-cortex-m", path = "arch/cortex_m.rs")]
38#[cfg_attr(feature = "arch-riscv32", path = "arch/riscv32.rs")]
39#[cfg_attr(feature = "arch-std", path = "arch/std.rs")]
40#[cfg_attr(feature = "arch-wasm", path = "arch/wasm.rs")]
41#[cfg_attr(feature = "arch-spin", path = "arch/spin.rs")]
42mod arch;
43
44#[cfg(feature = "_arch")]
45#[allow(unused_imports)] // don't warn if the module is empty.
46pub use arch::*;
47
48pub mod raw;
49
50mod spawner;
51pub use spawner::*;
52
53mod config {
54    #![allow(unused)]
55    include!(concat!(env!("OUT_DIR"), "/config.rs"));
56}
57
58/// Implementation details for embassy macros.
59/// Do not use. Used for macros and HALs only. Not covered by semver guarantees.
60#[doc(hidden)]
61#[cfg(not(feature = "nightly"))]
62pub mod _export {
63    use core::alloc::Layout;
64    use core::cell::{Cell, UnsafeCell};
65    use core::future::Future;
66    use core::mem::MaybeUninit;
67    use core::ptr::null_mut;
68
69    use critical_section::{CriticalSection, Mutex};
70
71    use crate::raw::TaskPool;
72
73    struct Arena<const N: usize> {
74        buf: UnsafeCell<MaybeUninit<[u8; N]>>,
75        ptr: Mutex<Cell<*mut u8>>,
76    }
77
78    unsafe impl<const N: usize> Sync for Arena<N> {}
79    unsafe impl<const N: usize> Send for Arena<N> {}
80
81    impl<const N: usize> Arena<N> {
82        const fn new() -> Self {
83            Self {
84                buf: UnsafeCell::new(MaybeUninit::uninit()),
85                ptr: Mutex::new(Cell::new(null_mut())),
86            }
87        }
88
89        fn alloc<T>(&'static self, cs: CriticalSection) -> &'static mut MaybeUninit<T> {
90            let layout = Layout::new::<T>();
91
92            let start = self.buf.get().cast::<u8>();
93            let end = unsafe { start.add(N) };
94
95            let mut ptr = self.ptr.borrow(cs).get();
96            if ptr.is_null() {
97                ptr = self.buf.get().cast::<u8>();
98            }
99
100            let bytes_left = (end as usize) - (ptr as usize);
101            let align_offset = (ptr as usize).next_multiple_of(layout.align()) - (ptr as usize);
102
103            if align_offset + layout.size() > bytes_left {
104                panic!("embassy-executor: task arena is full. You must increase the arena size, see the documentation for details: https://docs.embassy.dev/embassy-executor/");
105            }
106
107            let res = unsafe { ptr.add(align_offset) };
108            let ptr = unsafe { ptr.add(align_offset + layout.size()) };
109
110            self.ptr.borrow(cs).set(ptr);
111
112            unsafe { &mut *(res as *mut MaybeUninit<T>) }
113        }
114    }
115
116    static ARENA: Arena<{ crate::config::TASK_ARENA_SIZE }> = Arena::new();
117
118    pub struct TaskPoolRef {
119        // type-erased `&'static mut TaskPool<F, N>`
120        // Needed because statics can't have generics.
121        ptr: Mutex<Cell<*mut ()>>,
122    }
123    unsafe impl Sync for TaskPoolRef {}
124    unsafe impl Send for TaskPoolRef {}
125
126    impl TaskPoolRef {
127        pub const fn new() -> Self {
128            Self {
129                ptr: Mutex::new(Cell::new(null_mut())),
130            }
131        }
132
133        /// Get the pool for this ref, allocating it from the arena the first time.
134        ///
135        /// safety: for a given TaskPoolRef instance, must always call with the exact
136        /// same generic params.
137        pub unsafe fn get<F: Future, const N: usize>(&'static self) -> &'static TaskPool<F, N> {
138            critical_section::with(|cs| {
139                let ptr = self.ptr.borrow(cs);
140                if ptr.get().is_null() {
141                    let pool = ARENA.alloc::<TaskPool<F, N>>(cs);
142                    pool.write(TaskPool::new());
143                    ptr.set(pool as *mut _ as _);
144                }
145
146                unsafe { &*(ptr.get() as *const _) }
147            })
148        }
149    }
150}
embassy_executor/lib.rs

embassy_executor/
lib.rs
