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Date: Wed, 17 May 2023 18:07:09 +0800
From: "847567161" <847567161@...com>
To: "musl" <musl@...ts.openwall.com>
Subject: Question:Why musl call a_barrier in __pthread_once?

Hi,

Why musl add&nbsp;a_barrier() in if branch here?  
What happend if we remove it? Could you give me more details?

int __pthread_once(pthread_once_t *control, void (*init)(void))
{
	/* Return immediately if init finished before, but ensure that
	 * effects of the init routine are visible to the caller. */
	if (*(volatile int *)control == 2) {
		a_barrier();
		return 0;
	}
	return __pthread_once_full(control, init);
}

https://gitee.com/openharmony/third_party_musl/blob/master/src/thread/pthread_once.c#L44


Chuang Yin

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