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 once_cell instead of static mut #2958

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

use once_cell instead of static mut #2958

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.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
74 changes: 23 additions & 51 deletions tracing-core/src/dispatch.rs
View file
Open in desktop
Expand Up @@ -158,6 +158,8 @@ use alloc::sync::{Arc, Weak};
#[cfg(feature = "alloc")]
use core::ops::Deref;

use once_cell::sync::OnceCell;

/// `Dispatch` trace data to a [`Collect`].
#[derive(Clone)]
pub struct Dispatch {
Expand Down Expand Up @@ -214,21 +216,12 @@ thread_local! {
}

static EXISTS: AtomicBool = AtomicBool::new(false);
static GLOBAL_INIT: AtomicUsize = AtomicUsize::new(UNINITIALIZED);

#[cfg(feature = "std")]
static SCOPED_COUNT: AtomicUsize = AtomicUsize::new(0);

const UNINITIALIZED: usize = 0;
const INITIALIZING: usize = 1;
const INITIALIZED: usize = 2;
static GLOBAL_DISPATCH: OnceCell<Dispatch> = OnceCell::new();

static mut GLOBAL_DISPATCH: Dispatch = Dispatch {
#[cfg(feature = "alloc")]
collector: Kind::Global(&NO_COLLECTOR),
#[cfg(not(feature = "alloc"))]
collector: &NO_COLLECTOR,
};
static NONE: Dispatch = Dispatch {
#[cfg(feature = "alloc")]
collector: Kind::Global(&NO_COLLECTOR),
Expand Down Expand Up @@ -329,42 +322,28 @@ pub fn set_default(dispatcher: &Dispatch) -> DefaultGuard {
/// [span]: super::span
/// [`Event`]: super::event::Event
pub fn set_global_default(dispatcher: Dispatch) -> Result<(), SetGlobalDefaultError> {
// if `compare_exchange` returns Result::Ok(_), then `new` has been set and
// `current`—now the prior value—has been returned in the `Ok()` branch.
if GLOBAL_INIT
.compare_exchange(
UNINITIALIZED,
INITIALIZING,
Ordering::SeqCst,
Ordering::SeqCst,
)
.is_ok()
{
#[cfg(feature = "alloc")]
let collector = {
let collector = match dispatcher.collector {
Kind::Global(s) => s,
Kind::Scoped(s) => unsafe {
// safety: this leaks the collector onto the heap. the
// reference count will always be at least 1.
&*Arc::into_raw(s)
},
};
Kind::Global(collector)
#[cfg(feature = "alloc")]
let collector = {
let collector = match dispatcher.collector {
Kind::Global(s) => s,
Kind::Scoped(s) => unsafe {
// safety: this leaks the collector onto the heap. the
// reference count will always be at least 1.
&*Arc::into_raw(s)
},
};
Kind::Global(collector)
};

#[cfg(not(feature = "alloc"))]
let collector = dispatcher.collector;
#[cfg(not(feature = "alloc"))]
let collector = dispatcher.collector;

unsafe {
GLOBAL_DISPATCH = Dispatch { collector };
}
GLOBAL_INIT.store(INITIALIZED, Ordering::SeqCst);
EXISTS.store(true, Ordering::Release);
Ok(())
} else {
Err(SetGlobalDefaultError { _no_construct: () })
}
let result = GLOBAL_DISPATCH
.set(Dispatch { collector })
.map_err(|_| SetGlobalDefaultError { _no_construct: () });
EXISTS.store(true, Ordering::Release);

result
}

/// Returns true if a `tracing` dispatcher has ever been set.
Expand Down Expand Up @@ -504,14 +483,7 @@ where

#[inline(always)]
pub(crate) fn get_global() -> &'static Dispatch {
if GLOBAL_INIT.load(Ordering::Acquire) != INITIALIZED {
return &NONE;
}
unsafe {
// This is safe given the invariant that setting the global dispatcher
// also sets `GLOBAL_INIT` to `INITIALIZED`.
&GLOBAL_DISPATCH
}
GLOBAL_DISPATCH.get().unwrap_or(&NONE)
}

#[cfg(feature = "std")]
Expand Down