Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751998AbaBNKbR (ORCPT ); Fri, 14 Feb 2014 05:31:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:14617 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751797AbaBNKbP (ORCPT ); Fri, 14 Feb 2014 05:31:15 -0500 Message-ID: <52FDF000.5070609@redhat.com> Date: Fri, 14 Feb 2014 11:29:20 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: "Srivatsa S. Bhat" , paulus@samba.org, oleg@redhat.com, mingo@kernel.org, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org CC: paulmck@linux.vnet.ibm.com, tj@kernel.org, walken@google.com, ego@linux.vnet.ibm.com, linux@arm.linux.org.uk, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Christoffer Dall , Gleb Natapov , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 10/52] arm, kvm: Fix CPU hotplug callback registration References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> <20140214075122.22701.18462.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214075122.22701.18462.stgit@srivatsabhat.in.ibm.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 14/02/2014 08:51, Srivatsa S. Bhat ha scritto: > 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 kvm code in arm by using this latter form of callback registration. > > Cc: Christoffer Dall > Cc: Gleb Natapov > Cc: Paolo Bonzini > Cc: Russell King > Cc: Ingo Molnar > Cc: kvmarm@lists.cs.columbia.edu > Cc: kvm@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Srivatsa S. Bhat > --- > > arch/arm/kvm/arm.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index 1d8248e..147b917 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque) > } > } > > + cpu_notifier_register_begin(); > + > err = init_hyp_mode(); > if (err) > goto out_err; > > - err = register_cpu_notifier(&hyp_init_cpu_nb); > + err = __register_cpu_notifier(&hyp_init_cpu_nb); > if (err) { > kvm_err("Cannot register HYP init CPU notifier (%d)\n", err); > goto out_err; > } > > + cpu_notifier_register_done(); > + > hyp_cpu_pm_init(); > > kvm_coproc_table_init(); > return 0; > out_err: > + cpu_notifier_register_done(); > return err; > } > > Acked-by: Paolo Bonzini -- 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/