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Date: Mon, 26 Aug 2013 11:11:05 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com> 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: [RFC PATCH 08/11] trace-cmd: Apply the trace-msg protocol for communication between a server and clients On Mon, 26 Aug 2013 10:50:33 +0900 Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com> wrote: > <Network> > 0. old server and old client > Old servers send "tracecmd" as the first message. > Old clients compare the first 8byte of the first message with "tracecmd". > > 1. new server > - Send "tracecmd-v2" as the first message. > - Check the reply message whether the message is "tracecmd-v2" or cpus > value. > If "tracecmd-v2", the server uses new protocol and wait for the > message MSG_TINIT. > If cpus value, the server uses old protocol. That will kill an old client. Yes it only checks the first 8 bytes, but then it gets back a comma separated list of CPUs. As it uses TCP for this transaction, the unread "-v2" will end up being read as CPUs by the client. > > 2. new client > - Receive the first message. > - Check the message whether the message is "tracecmd-v2" or not. > If "tracecmd-v2", the client sends "tracecmd-v2" to the server. Then, > the client sends the message MSG_TINIT. > If "tracecmd", the client sends cpus value as the old protocol. > It will have to be the client that determines if the protocol is v2 or not. Basically, after receiving the "tracecmd" the client can send back "V2", and then expect the server to reply with "V2" as well. If the server does not, then it disconnects from the server and then restarts with the old protocol. > <Virtio-serial> > This is new feature, so trace-cmd does not need to keep backward > compatibility. Right, the virtio-serial will noly need to be supported by the v2 protocols. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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