From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e36.co.us.ibm.com (e36.co.us.ibm.com [32.97.110.154]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e36.co.us.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTP id B5FBA67BD9 for ; Mon, 20 Nov 2006 15:22:06 +1100 (EST) Received: from westrelay02.boulder.ibm.com (westrelay02.boulder.ibm.com [9.17.195.11]) by e36.co.us.ibm.com (8.13.8/8.12.11) with ESMTP id kAK4M3O2015078 for ; Sun, 19 Nov 2006 23:22:03 -0500 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by westrelay02.boulder.ibm.com (8.13.6/8.13.6/NCO v8.1.1) with ESMTP id kAK4M3Gb509980 for ; Sun, 19 Nov 2006 21:22:03 -0700 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id kAK4M2V7023880 for ; Sun, 19 Nov 2006 21:22:03 -0700 Message-ID: <45612D68.8080404@austin.ibm.com> Date: Sun, 19 Nov 2006 22:22:00 -0600 From: jschopp MIME-Version: 1.0 To: michael@ellerman.id.au Subject: Re: [PATCH] Reorganise and then fixup the pseries cpu hotplug code References: <20061116154051.GB2008@localdomain> <20061117033638.0E24B67BCE@ozlabs.org> <20061117180456.GG23600@austin.ibm.com> <1163984914.7832.16.camel@localhost.localdomain> In-Reply-To: <1163984914.7832.16.camel@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: srinivasa@in.ibm.com, ego@in.ibm.com, linuxppc-dev@ozlabs.org, paulus@samba.org, Anton Blanchard , ntl@pobox.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , >>> + /* Isolation and deallocation are definatly done by >> ^^^^^^^^^ >> typo That word definitely gives me trouble. I'd imagine the typo originated with me. >> >>> + * drslot_chrp_cpu. If they were not they would be >>> + * done here. Change isolate state to Isolate and >>> + * change allocation-state to Unusable. >>> + */ >>> + paca[cpu].cpu_start = 0; >> I can't figure out what the comment means with respect >> to this code ... > > Me either. It's unchanged from the original merge of cpu hotplug: > http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=24c13f21f0a6abe07020a959990da2b134e6734f > http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=blobdiff;h=72144b6122f9336e7fa242e50b65b099df0cd72b;hp=f671515c0676e61064ae414273fa4546d0c04938;hb=24c13f21f0a6abe07020a959990da2b134e6734f;f=arch/ppc64/kernel/smp.c > > Which carries the name of one Joel Schopp :) > > Grepping the tree at that point finds no other mention of > drslot_chrp_cpu, so I think it's a stale comment - we should probably > just rip it out - Joel? It might be clearer by saying "the userspace program drslot_chrp_cpu" or "isolation and deallocation occur in userspace, so just stop the cpu. If isolation and deallocation ever move from userpace to kernel space they would go here". On pseries dynamic partitioning or cpu guard (the things that initiate a cpu hotplug) all call a userspace program drmgr, which calls drslot_chrp_cpu, which then talks to the firmware to isolate and unallocate (on remove, the opposite on add) after it has hotplug removed the cpu via the /sys interface. This allows the cpu to be reassigned to another partition. At least that's what I remember from back then when we did it. Though I don't think it's changed any. Feel free to make the comment more intelligible.