Date: Fri, 09 Jul 2010 20:58:05 +0200 From: Gabor PALI <pgj@FreeBSD.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: svn-src-head@freebsd.org Subject: Re: svn commit: r209119 - head/sys/sys Message-ID: <4C37713D.5060202@FreeBSD.org> In-Reply-To: <alpine.BSF.2.00.1007091949170.94277@fledge.watson.org> References: <4C376B0E.9050505@FreeBSD.org> <alpine.BSF.2.00.1007091949170.94277@fledge.watson.org>
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On 07/09/10 20:50, Robert Watson wrote: > I think I have an e-mail in my in queue from you suggesting an > alternative approach that I haven't yet gotten to due to utter > saturation here. That is why I CC'ed svn-src-head@ :) (But I do not see any sign whether my last email reached it -- I am not an that list.) I hope other committers will help me with this, because I would like to use it in my project, and I think it would be useful in general. > I assume there are reasonable alternatives that work around the > potential race with a small probability of a missed or extra update, > or similar, which would be fine. In a few words: As far as I know, 64-bit atomic counters could be implemented by using cmpxchg8b or by a plain uint64_t variable protected by some kind of locking(9). Cheers, :g
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