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From: =?gb18030?B?ODQ3NTY3MTYx?= <847567161@qq.com>
To: =?gb18030?B?bXVzbA==?= <musl@lists.openwall.com>
Subject: [musl] =?gb18030?B?UXVlc3Rpb26juldoeSBtdXNsIGNhbGyBMIQyYV9iYXJyaWVyIGluIF9fcHRocmVhZF9vbmNlPw==?=
Date: Wed, 17 May 2023 18:07:09 +0800	[thread overview]
Message-ID: <tencent_AB6D68C5E505BB0AB73CAFC159C6F7E47D0A@qq.com> (raw)

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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

             reply	other threads:[~2023-05-17 10:07 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-17 10:07 =?gb18030?B?ODQ3NTY3MTYx?= [this message]
2023-05-17 10:37 ` [musl] Question：Why musl call a_barrier in __pthread_once? alice
2023-05-17 11:17 ` NRK
2023-05-17 12:11   ` =?gb18030?B?UmU6IFttdXNsXSBRdWVzdGlvbqO6V2h5IG11c2wgY2FsbIEwhDJhX2JhcnJpZXIgaW4gX19wdGhyZWFkX29uY2U/?= =?gb18030?B?ODQ3NTY3MTYx?=
2023-05-17 13:12   ` [musl] Question：Why musl call a_barrier in __pthread_once? Rich Felker

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