Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752222AbaBKRSq (ORCPT ); Tue, 11 Feb 2014 12:18:46 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:32923 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750934AbaBKRSo (ORCPT ); Tue, 11 Feb 2014 12:18:44 -0500 Date: Tue, 11 Feb 2014 22:48:05 +0530 From: Gautham R Shenoy To: Toshi Kani Cc: "Srivatsa S. Bhat" , "paulus@samba.org" , "oleg@redhat.com" , "rusty@rustcorp.com.au" , "peterz@infradead.org" , "tglx@linutronix.de" , "akpm@linux-foundation.org" , "mingo@kernel.org" , "paulmck@linux.vnet.ibm.com" , "tj@kernel.org" , "walken@google.com" , "ego@linux.vnet.ibm.com" , "linux@arm.linux.org.uk" , "linux-kernel@vger.kernel.org" , "Rafael J. Wysocki" Subject: Re: [PATCH 01/51] CPU hotplug: Provide lockless versions of callback registration functions Message-ID: <20140211171805.GA3932@in.ibm.com> Reply-To: ego@linux.vnet.ibm.com References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> <20140205220447.19080.9460.stgit@srivatsabhat.in.ibm.com> <1392081980.5612.123.camel@misato.fc.hp.com> <52F9ED11.5010800@linux.vnet.ibm.com> <1392136436.5612.131.camel@misato.fc.hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392136436.5612.131.camel@misato.fc.hp.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021117-0320-0000-0000-0000026FA1C0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 11, 2014 at 09:33:56AM -0700, Toshi Kani wrote: > > I agree that introducing a reader-writer semaphore allows concurrent > executions. Adding yet another hotplug lock is a bit unfortunate, > though. > I agree with this last part. We already have enough locks for cpu-hotplug. Another one sounds one too many!! > This may be a dumb question, but can't we simply do this way? > > get_online_cpus(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > put_online_cpus(); > -------- Someone chooses to hotplug a cpu here ------ -------- But this subsystem might miss out on knowing about it since it hasn't registered its notifier yet! > register_cpu_notifier(&foobar_cpu_notifier); > > Thanks, > -Toshi > -- Thanks and Regards gautham. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/