From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: 马磊 <aware.why@gmail.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [Problem] about src/xen/include/public/io/ring.h
Date: Mon, 8 Apr 2013 09:32:18 -0400 [thread overview]
Message-ID: <20130408133218.GH27445@phenom.dumpdata.com> (raw)
In-Reply-To: <CA+ePHTDaC6VLXnCPUg3ByW5VTzbzqiRQ8-4qtUB3OJsUM=ztrg@mail.gmail.com>
On Mon, Apr 08, 2013 at 04:10:49PM +0800, 马磊 wrote:
> Hi,
> there is a macro in io/ring.h as follows:
>
> 211#define RING_HAS_UNCONSUMED_REQUESTS(_r) ({
> \ |
> 212 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons;
> \
> 213 unsigned int rsp = RING_SIZE(_r) -
> \
> 214 ((_r)->req_cons - (_r)->rsp_prod_pvt);
> \
> 215 req < rsp ? req : rsp;
> \
> 216})
>
> Anyone could explain this?
Which part are you unclear about?
I might be easier if you deconstruct the macro and write out
inthe code. That should give you an idea of what it does.
<hint: Figure out first what RING_SIZE comes out to>
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> http://lists.xen.org/xen-devel
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next prev parent reply other threads:[~2013-04-08 13:32 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-08 8:10 [Problem] about src/xen/include/public/io/ring.h 马磊
2013-04-08 13:32 ` Konrad Rzeszutek Wilk [this message]
2013-04-09 3:05 ` 马磊
2013-04-10 13:15 ` Konrad Rzeszutek Wilk
2013-04-11 7:46 ` 马磊
2013-04-11 13:20 ` Konrad Rzeszutek Wilk
2013-04-12 2:21 ` 马磊
2013-04-12 7:49 ` Ian Campbell
2013-04-12 10:35 ` 马磊
2013-04-12 11:14 ` Ian Campbell
2013-04-12 11:24 ` 马磊
2013-04-12 13:45 ` Konrad Rzeszutek Wilk
2013-04-15 2:52 ` 马磊
2013-04-10 6:20 ` 马磊
2013-04-10 13:15 ` Konrad Rzeszutek Wilk
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