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core: additional deprecation fixes #1606

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merged 3 commits into from
Oct 1, 2021
Merged

core: additional deprecation fixes #1606

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426e07a
core: additional deprecation fixes
hawkw Oct 1, 2021
22c7ea6
fix status not being updated if cas fails
hawkw Oct 1, 2021
1879769
there we go
hawkw Oct 1, 2021
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53 changes: 34 additions & 19 deletions tracing-core/src/spin/once.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -76,31 +76,41 @@ impl<T> Once<T> {
let mut status = self.state.load(Ordering::SeqCst);

if status == INCOMPLETE {
status = self
.state
.compare_and_swap(INCOMPLETE, RUNNING, Ordering::SeqCst);
if status == INCOMPLETE {
// We init
// We use a guard (Finish) to catch panics caused by builder
let mut finish = Finish {
state: &self.state,
panicked: true,
};
unsafe { *self.data.get() = Some(builder()) };
finish.panicked = false;

status = COMPLETE;
self.state.store(status, Ordering::SeqCst);

// This next line is strictly an optimization
return self.force_get();
status = match self.state.compare_exchange(
INCOMPLETE,
RUNNING,
Ordering::SeqCst,
Ordering::SeqCst,
) {
Ok(status) => {
debug_assert_eq!(
status, INCOMPLETE,
"if compare_exchange succeeded, previous status must be incomplete",
);
// We init
// We use a guard (Finish) to catch panics caused by builder
let mut finish = Finish {
state: &self.state,
panicked: true,
};
unsafe { *self.data.get() = Some(builder()) };
finish.panicked = false;

self.state.store(COMPLETE, Ordering::SeqCst);

// This next line is strictly an optimization
return self.force_get();
}
Err(status) => status,
}
}

loop {
match status {
INCOMPLETE => unreachable!(),
RUNNING => {
// TODO(eliza): replace with `core::hint::spin_loop` once our MSRV supports it.
#[allow(deprecated)]
// We spin
cpu_relax();
status = self.state.load(Ordering::SeqCst)
Expand All @@ -126,7 +136,12 @@ impl<T> Once<T> {
loop {
match self.state.load(Ordering::SeqCst) {
INCOMPLETE => return None,
RUNNING => cpu_relax(), // We spin

RUNNING => {
// TODO(eliza): replace with `core::hint::spin_loop` once our MSRV supports it.
#[allow(deprecated)]
cpu_relax() // We spin
}
COMPLETE => return Some(self.force_get()),
PANICKED => panic!("Once has panicked"),
_ => unsafe { unreachable() },
Expand Down