pub fn spin_loop()
Expand description
Emits a machine instruction to signal the processor that it is running in a busy-wait spin-loop (“spin lock”).
Upon receiving the spin-loop signal the processor can optimize its behavior by, for example, saving power or switching hyper-threads.
This function is different from thread::yield_now
which directly
yields to the system’s scheduler, whereas spin_loop
does not interact
with the operating system.
A common use case for spin_loop
is implementing bounded optimistic
spinning in a CAS loop in synchronization primitives. To avoid problems
like priority inversion, it is strongly recommended that the spin loop is
terminated after a finite amount of iterations and an appropriate blocking
syscall is made.
Note: On platforms that do not support receiving spin-loop hints this function does not do anything at all.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use std::{hint, thread};
// A shared atomic value that threads will use to coordinate
let live = Arc::new(AtomicBool::new(false));
// In a background thread we'll eventually set the value
let bg_work = {
let live = live.clone();
thread::spawn(move || {
// Do some work, then make the value live
do_some_work();
live.store(true, Ordering::Release);
})
};
// Back on our current thread, we wait for the value to be set
while !live.load(Ordering::Acquire) {
// The spin loop is a hint to the CPU that we're waiting, but probably
// not for very long
hint::spin_loop();
}
// The value is now set
do_some_work();
bg_work.join()?;
Run