From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Mon, 21 Jun 2010 10:40:57 -0400
To: 9fans@9fans.net
Message-ID: <a4c3e91d8044dc47b504fab2bf11aa54@kw.quanstro.net>
In-Reply-To: <AANLkTimysByILLkzs6Fs5XfqxmXcQNB3tazBtgbIhHiw@mail.gmail.com>
References: <97d3416a6d7cadb18e8723fff3d2e2a8@hamnavoe.com>
	<da2c7d30ad147fca47014c09d339aa1b@kw.quanstro.net>
	<81727c869e97f501968f868ee8794852@kw.quanstro.net>
	<AANLkTimysByILLkzs6Fs5XfqxmXcQNB3tazBtgbIhHiw@mail.gmail.com>
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Subject: Re: [9fans] interesting timing tests
Topicbox-Message-UUID: 35f4b082-ead6-11e9-9d60-3106f5b1d025

void
lock(ulong *l)
{
	ulong old;
	ushort next, owner;

	old = _xadd(l, 1);
	for(;;){
		next = old;
		owner = old>>16;
		old = *l;
		if(next == owner)
			break;
	}
}

void
unlock(ulong *l)
{
	_xadd(l, 1<<16);
}

- erik