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Relax memory ordering used in SameMutexCheck #96619

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merged 3 commits into from May 5, 2022
Merged

Relax memory ordering used in SameMutexCheck #96619

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df4457e
Relax memory ordering used in SameMutexCheck
May 1, 2022
a05df2e
Fix formatting
May 2, 2022
55a7d18
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May 2, 2022
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10 changes: 8 additions & 2 deletions library/std/src/sys_common/condvar/check.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,8 +24,14 @@ impl SameMutexCheck {
}
pub fn verify(&self, mutex: &MovableMutex) {
let addr = mutex.raw() as *const imp::Mutex as *const () as *mut _;
match self.addr.compare_exchange(ptr::null_mut(), addr, Ordering::SeqCst, Ordering::SeqCst)
{
// Relaxed is okay here because we never read through `self.addr`, and only use it to
// compare addresses.
match self.addr.compare_exchange(
ptr::null_mut(),
addr,
Ordering::Relaxed,
Ordering::Relaxed,
) {
Ok(_) => {} // Stored the address
Err(n) if n == addr => {} // Lost a race to store the same address
_ => panic!("attempted to use a condition variable with two mutexes"),
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