linux-kernel - Re: Re: [RFC PATCH 08/11] trace-cmd: Apply the trace-msg protocol for communication between a server and clients

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Date:	Thu, 29 Aug 2013 10:57:09 +0900
From:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org, yrl.pp-manager.tt@...achi.com
Subject: Re: Re: [RFC PATCH 08/11] trace-cmd: Apply the trace-msg protocol
 for communication between a server and clients

(2013/08/28 23:42), Steven Rostedt wrote:
> On Wed, 28 Aug 2013 20:30:17 +0900
> Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com> wrote:
>
>> (2013/08/27 22:05), Steven Rostedt wrote:
>>> On Tue, 27 Aug 2013 19:23:24 +0900
>>> Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com> wrote:
>>>
>>>> OK, let me check that. Even if the old server will receive "V2", the
>>>> server will send port numbers instead of "V2" due to the old protocol.
>>>> In that time, the new client will disconnect from the old server and
>>>> the restarts with the old protocol. Is it OK?
>>>
>>> Yep, that's exactly what I meant ;-)
>>
>> I tried to implement the feature, but I found that sending just "V2"
>> from the new client is inappropriate. This is because the old server
>> doesn't respond to the client before receiving cpu numbers, page size,
>> and options. So, when the new client sends the first message, it should
>> send "V2\0<MAGIC_NUMBER>\00\0", I think. If so, the old server will
>> understand the message as cpus=0, pagesize=<MAGIC_NUMBER>, options=0,
>> and then it will send port numbers(actually \0). Note if <MAGIC_NUMBER>
>> is zero, the old server will die.
>>
>> Can I implement the first message of the new client as
>> "V2\0<MAGIC_NUMBER>\00\0"?
>>
>
> If it works for both old and new server with old and new client (and
> all combinations) I'm fine with it.

OK, I'll submit trace-cmd patches as V2 in a few days.

Thanks,
Yoshihiro YUNOMAE

-- 
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@...achi.com


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