mirror of https://github.com/torvalds/linux.git
63 lines
1.9 KiB
Rust
63 lines
1.9 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
|
|
|
|
use std::fmt::{self, Debug};
|
|
use std::thread::{self, ThreadId};
|
|
|
|
/// ThreadBound is a Sync-maker and Send-maker that allows accessing a value
|
|
/// of type T only from the original thread on which the ThreadBound was
|
|
/// constructed.
|
|
pub(crate) struct ThreadBound<T> {
|
|
value: T,
|
|
thread_id: ThreadId,
|
|
}
|
|
|
|
unsafe impl<T> Sync for ThreadBound<T> {}
|
|
|
|
// Send bound requires Copy, as otherwise Drop could run in the wrong place.
|
|
//
|
|
// Today Copy and Drop are mutually exclusive so `T: Copy` implies `T: !Drop`.
|
|
// This impl needs to be revisited if that restriction is relaxed in the future.
|
|
unsafe impl<T: Copy> Send for ThreadBound<T> {}
|
|
|
|
impl<T> ThreadBound<T> {
|
|
pub(crate) fn new(value: T) -> Self {
|
|
ThreadBound {
|
|
value,
|
|
thread_id: thread::current().id(),
|
|
}
|
|
}
|
|
|
|
pub(crate) fn get(&self) -> Option<&T> {
|
|
if thread::current().id() == self.thread_id {
|
|
Some(&self.value)
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<T: Debug> Debug for ThreadBound<T> {
|
|
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
|
match self.get() {
|
|
Some(value) => Debug::fmt(value, formatter),
|
|
None => formatter.write_str("unknown"),
|
|
}
|
|
}
|
|
}
|
|
|
|
// Copy the bytes of T, even if the currently running thread is the "wrong"
|
|
// thread. This is fine as long as the original thread is not simultaneously
|
|
// mutating this value via interior mutability, which would be a data race.
|
|
//
|
|
// Currently `T: Copy` is sufficient to guarantee that T contains no interior
|
|
// mutability, because _all_ interior mutability in Rust is built on
|
|
// std::cell::UnsafeCell, which has no Copy impl. This impl needs to be
|
|
// revisited if that restriction is relaxed in the future.
|
|
impl<T: Copy> Copy for ThreadBound<T> {}
|
|
|
|
impl<T: Copy> Clone for ThreadBound<T> {
|
|
fn clone(&self) -> Self {
|
|
*self
|
|
}
|
|
}
|