Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Use UnsafeCell for fast constant thread locals #122583

Merged
merged 1 commit into from
Mar 16, 2024
Merged

Use UnsafeCell for fast constant thread locals #122583

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
15 changes: 7 additions & 8 deletions library/std/src/sys/thread_local/fast_local.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,22 13,21 @@ pub macro thread_local_inner {
(@key $t:ty, const $init:expr) => {{
#[inline]
#[deny(unsafe_op_in_unsafe_fn)]
// FIXME: Use `SyncUnsafeCell` instead of allowing `static_mut_refs` lint
#[cfg_attr(bootstrap, allow(static_mut_ref))]
#[cfg_attr(not(bootstrap), allow(static_mut_refs))]
unsafe fn __getit(
_init: $crate::option::Option<&mut $crate::option::Option<$t>>,
) -> $crate::option::Option<&'static $t> {
const INIT_EXPR: $t = $init;
// If the platform has support for `#[thread_local]`, use it.
#[thread_local]
static mut VAL: $t = INIT_EXPR;
// We use `UnsafeCell` here instead of `static mut` to ensure any generated TLS shims
// have a nonnull attribute on their return value.
joboet marked this conversation as resolved.
Show resolved Hide resolved
static VAL: $crate::cell::UnsafeCell<$t> = $crate::cell::UnsafeCell::new(INIT_EXPR);

// If a dtor isn't needed we can do something "very raw" and
// just get going.
if !$crate::mem::needs_drop::<$t>() {
unsafe {
return $crate::option::Option::Some(&VAL)
return $crate::option::Option::Some(&*VAL.get())
}
}

Expand All @@ -55,15 54,15 @@ pub macro thread_local_inner {
// so now.
0 => {
$crate::thread::local_impl::Key::<$t>::register_dtor(
$crate::ptr::addr_of_mut!(VAL) as *mut $crate::primitive::u8,
VAL.get() as *mut $crate::primitive::u8,
destroy,
);
STATE.set(1);
$crate::option::Option::Some(&VAL)
$crate::option::Option::Some(&*VAL.get())
}
// 1 == the destructor is registered and the value
// is valid, so return the pointer.
1 => $crate::option::Option::Some(&VAL),
1 => $crate::option::Option::Some(&*VAL.get()),
// otherwise the destructor has already run, so we
// can't give access.
_ => $crate::option::Option::None,
Expand Down
Loading