vendor/jemalloc-sys/rep/include/jemalloc/internal/spin.h

#ifndef JEMALLOC_INTERNAL_SPIN_H
#define JEMALLOC_INTERNAL_SPIN_H

#define SPIN_INITIALIZER {0U}

typedef struct {
	unsigned iteration;
} spin_t;

static inline void
spin_cpu_spinwait() {
#  if HAVE_CPU_SPINWAIT
	CPU_SPINWAIT;
#  else
	volatile int x = 0;
	x = x;
#  endif
}

static inline void
spin_adaptive(spin_t *spin) {
	volatile uint32_t i;

	if (spin->iteration < 5) {
		for (i = 0; i < (1U << spin->iteration); i++) {
			spin_cpu_spinwait();
		}
		spin->iteration++;
	} else {
#ifdef _WIN32
		SwitchToThread();
#else
		sched_yield();
#endif
	}
}

#undef SPIN_INLINE

#endif /* JEMALLOC_INTERNAL_SPIN_H */