mailing list of musl libc

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 #include "pthread_impl.h"

void __lock(volatile int *addr)
{
	if (libc.threads_minus_1) {
		int volatile* waiters = addr+1;
		for (;;) {
			for (int spins = 0; spins < 10000; ++spins) {
				if (a_tas(addr)) a_spin();
				else {
					/* a lock must ensure that all data
					   that is written before will be
					   visible */
					a_aqf();
					return;
				}
			}
			a_inc(waiters);
			__syscall(SYS_futex, addr, FUTEX_WAIT|THRD_PRIVATE, 1, 0);
			a_dec(waiters);
		}
	}
}

void __unlock(volatile int *l)
{
	a_spunl(l);
	if (l[1]) __wake_priv(l, 1);
}