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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263// 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 }}