From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 13 Dec 2007 12:58:52 +0000 (GMT) Received: from localhost.localdomain ([127.0.0.1]:61149 "EHLO dl5rb.ham-radio-op.net") by ftp.linux-mips.org with ESMTP id S28575685AbXLMM6t (ORCPT ); Thu, 13 Dec 2007 12:58:49 +0000 Received: from denk.linux-mips.net (denk.linux-mips.net [127.0.0.1]) by dl5rb.ham-radio-op.net (8.14.1/8.13.8) with ESMTP id lBDCwm14001441; Thu, 13 Dec 2007 12:58:49 GMT Received: (from ralf@localhost) by denk.linux-mips.net (8.14.1/8.14.1/Submit) id lBDCwlx5001440; Thu, 13 Dec 2007 12:58:47 GMT Date: Thu, 13 Dec 2007 12:58:47 +0000 From: Ralf Baechle To: Nilanjan Roychowdhury Cc: linux-mips@linux-mips.org Subject: Re: Inter processor synchronization Message-ID: <20071213125847.GA1352@linux-mips.org> References: <9D98C51005D80D43A19A3DF329A61D690106A282@INDEXCH2003.gmi.domain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9D98C51005D80D43A19A3DF329A61D690106A282@INDEXCH2003.gmi.domain> User-Agent: Mutt/1.5.17 (2007-11-01) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 17806 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Thu, Dec 13, 2007 at 09:07:20AM +0530, Nilanjan Roychowdhury wrote: > I have a scenario where two images of the same Linux kernel are running > on two MIPS cores. One is 24K and another is 4KEC. What is the best way > to achieve inter processor synchronization between them? > > I guess the locks for LL/SC are local to a particular core and can not > be extended across a multi core system. 4K and 24K cores don't support cache coherency. So SMP is out of question. This is a _total_ showstopper for SMP, don't waste your time thinking on possible workarounds. The you could do is some sort of clusting, running two OS images, one on the 4K and one on the 24K which would communicate through a carefully cache managed or even uncached shared memory region. > Will it be easier for me if both of them becomes same core ( like both > 24k) and I run the SMP version of Linux. Within limits Linux supports mixing different CPU types such as R4000MC / R4400MC and R10000 / R12000 / R14000 mixes because those processors are similar enough Ralf