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std: Avoid usage of Once in Instant #59676

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Apr 4, 2019
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27 changes: 20 additions & 7 deletions src/libstd/sys/unix/time.rs
Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,8 @@ impl Hash for Timespec {
#[cfg(any(target_os = "macos", target_os = "ios"))]
mod inner {
use crate::fmt;
use crate::sync::Once;
use crate::mem;
use crate::sync::atomic::{AtomicUsize, Ordering::SeqCst};
use crate::sys::cvt;
use crate::sys_common::mul_div_u64;
use crate::time::Duration;
Expand Down Expand Up @@ -229,18 +230,30 @@ mod inner {
Some(mul_div_u64(nanos, info.denom as u64, info.numer as u64))
}

fn info() -> &'static libc::mach_timebase_info {
fn info() -> libc::mach_timebase_info {
static mut INFO: libc::mach_timebase_info = libc::mach_timebase_info {
numer: 0,
denom: 0,
};
static ONCE: Once = Once::new();
static STATE: AtomicUsize = AtomicUsize::new(0);

unsafe {
ONCE.call_once(|| {
libc::mach_timebase_info(&mut INFO);
});
&INFO
// If a previous thread has filled in this global state, use that.
if STATE.load(SeqCst) == 2 {
return INFO;
}

// ... otherwise learn for ourselves ...
let mut info = mem::zeroed();
libc::mach_timebase_info(&mut info);

// ... and attempt to be the one thread that stores it globally for
// all other threads
if STATE.compare_exchange(0, 1, SeqCst, SeqCst).is_ok() {
INFO = info;
STATE.store(2, SeqCst);
}
return info;
}
}
}
Expand Down
24 changes: 18 additions & 6 deletions src/libstd/sys/windows/time.rs
Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,7 @@ fn intervals2dur(intervals: u64) -> Duration {

mod perf_counter {
use super::{NANOS_PER_SEC};
use crate::sync::Once;
use crate::sync::atomic::{AtomicUsize, Ordering::SeqCst};
use crate::sys_common::mul_div_u64;
use crate::sys::c;
use crate::sys::cvt;
Expand Down Expand Up @@ -210,13 +210,25 @@ mod perf_counter {

fn frequency() -> c::LARGE_INTEGER {
static mut FREQUENCY: c::LARGE_INTEGER = 0;
static ONCE: Once = Once::new();
static STATE: AtomicUsize = AtomicUsize::new(0);

unsafe {
ONCE.call_once(|| {
cvt(c::QueryPerformanceFrequency(&mut FREQUENCY)).unwrap();
});
FREQUENCY
// If a previous thread has filled in this global state, use that.
if STATE.load(SeqCst) == 2 {
return FREQUENCY;
}

// ... otherwise learn for ourselves ...
let mut frequency = 0;
cvt(c::QueryPerformanceFrequency(&mut frequency)).unwrap();

// ... and attempt to be the one thread that stores it globally for
// all other threads
if STATE.compare_exchange(0, 1, SeqCst, SeqCst).is_ok() {
FREQUENCY = frequency;
STATE.store(2, SeqCst);
}
return frequency;
}
}

Expand Down
27 changes: 27 additions & 0 deletions src/test/run-pass/issue-59020.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
// edition:2018
// run-pass
// ignore-emscripten no threads support

use std::thread;
use std::time::Duration;

fn main() {
let t1 = thread::spawn(|| {
let sleep = Duration::new(0,100_000);
for _ in 0..100 {
println!("Parking1");
thread::park_timeout(sleep);
}
});

let t2 = thread::spawn(|| {
let sleep = Duration::new(0,100_000);
for _ in 0..100 {
println!("Parking2");
thread::park_timeout(sleep);
}
});

t1.join().expect("Couldn't join thread 1");
t2.join().expect("Couldn't join thread 2");
}