From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: Re: [PATCH v3 36/52] zsmalloc: Fix CPU hotplug callback registration Date: Fri, 14 Mar 2014 15:41:08 +0900 Message-ID: <20140314064108.GD20556@bbox> References: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> <20140310203959.10746.61303.stgit@srivatsabhat.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:64356 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755663AbaCNGko (ORCPT ); Fri, 14 Mar 2014 02:40:44 -0400 Content-Disposition: inline In-Reply-To: <20140310203959.10746.61303.stgit@srivatsabhat.in.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Srivatsa S. Bhat" Cc: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rjw@rjwysocki.net, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.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, linux-arch@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@ozlabs.org, Nitin Gupta , linux-mm@kvack.org On Tue, Mar 11, 2014 at 02:09:59AM +0530, Srivatsa S. Bhat wrote: > Subsystems that want to register CPU hotplug callbacks, as well as perform > initialization for the CPUs that are already online, often do it as shown > below: > > get_online_cpus(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > register_cpu_notifier(&foobar_cpu_notifier); > > put_online_cpus(); > > This is wrong, since it is prone to ABBA deadlocks involving the > cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently > with CPU hotplug operations). > > Instead, the correct and race-free way of performing the callback > registration is: > > cpu_notifier_register_begin(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > /* Note the use of the double underscored version of the API */ > __register_cpu_notifier(&foobar_cpu_notifier); > > cpu_notifier_register_done(); > > > Fix the zsmalloc code by using this latter form of callback registration. > > Cc: Minchan Kim > Cc: Nitin Gupta > Cc: Ingo Molnar > Cc: linux-mm@kvack.org > Signed-off-by: Srivatsa S. Bhat Acked-by: Minchan Kim Thanks. -- Kind regards, Minchan Kim