Synchronize with all calls to unpark
in id-based thread parker
#114591
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The documentation for
thread::park
guarantees that "park synchronizes-with all prior unpark operations". In the id-based thread parking implementation, this is not implemented correctly, as the state variable is reset with a simple store, so there will not be a synchronizes-with edge if anunpark
happens just before the reset. This PR corrects this, replacing the load-check-reset sequence with a singlecompare_exchange
.