You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
78 lines
2.7 KiB
Rust
78 lines
2.7 KiB
Rust
// SPDX-License-Identifier: MIT OR Apache-2.0
|
|
//
|
|
// Copyright (c) 2020-2023 Andre Richter <andre.o.richter@gmail.com>
|
|
|
|
//! Synchronization primitives.
|
|
//!
|
|
//! # Resources
|
|
//!
|
|
//! - <https://doc.rust-lang.org/book/ch16-04-extensible-concurrency-sync-and-send.html>
|
|
//! - <https://stackoverflow.com/questions/59428096/understanding-the-send-trait>
|
|
//! - <https://doc.rust-lang.org/std/cell/index.html>
|
|
|
|
use core::cell::UnsafeCell;
|
|
|
|
//--------------------------------------------------------------------------------------------------
|
|
// Public Definitions
|
|
//--------------------------------------------------------------------------------------------------
|
|
|
|
/// Synchronization interfaces.
|
|
pub mod interface {
|
|
|
|
/// Any object implementing this trait guarantees exclusive access to the data wrapped within
|
|
/// the Mutex for the duration of the provided closure.
|
|
pub trait Mutex {
|
|
/// The type of the data that is wrapped by this mutex.
|
|
type Data;
|
|
|
|
/// Locks the mutex and grants the closure temporary mutable access to the wrapped data.
|
|
fn lock<'a, R>(&'a self, f: impl FnOnce(&'a mut Self::Data) -> R) -> R;
|
|
}
|
|
}
|
|
|
|
/// A pseudo-lock for teaching purposes.
|
|
///
|
|
/// In contrast to a real Mutex implementation, does not protect against concurrent access from
|
|
/// other cores to the contained data. This part is preserved for later lessons.
|
|
///
|
|
/// The lock will only be used as long as it is safe to do so, i.e. as long as the kernel is
|
|
/// executing single-threaded, aka only running on a single core with interrupts disabled.
|
|
pub struct NullLock<T>
|
|
where
|
|
T: ?Sized,
|
|
{
|
|
data: UnsafeCell<T>,
|
|
}
|
|
|
|
//--------------------------------------------------------------------------------------------------
|
|
// Public Code
|
|
//--------------------------------------------------------------------------------------------------
|
|
|
|
unsafe impl<T> Send for NullLock<T> where T: ?Sized + Send {}
|
|
unsafe impl<T> Sync for NullLock<T> where T: ?Sized + Send {}
|
|
|
|
impl<T> NullLock<T> {
|
|
/// Create an instance.
|
|
pub const fn new(data: T) -> Self {
|
|
Self {
|
|
data: UnsafeCell::new(data),
|
|
}
|
|
}
|
|
}
|
|
|
|
//------------------------------------------------------------------------------
|
|
// OS Interface Code
|
|
//------------------------------------------------------------------------------
|
|
|
|
impl<T> interface::Mutex for NullLock<T> {
|
|
type Data = T;
|
|
|
|
fn lock<'a, R>(&'a self, f: impl FnOnce(&'a mut Self::Data) -> R) -> R {
|
|
// In a real lock, there would be code encapsulating this line that ensures that this
|
|
// mutable reference will ever only be given out once at a time.
|
|
let data = unsafe { &mut *self.data.get() };
|
|
|
|
f(data)
|
|
}
|
|
}
|