From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v3 13/52] sparc, sysfs: Fix CPU hotplug callback registration Date: Tue, 11 Mar 2014 02:06:09 +0530 Message-ID: <20140310203609.10746.87407.stgit@srivatsabhat.in.ibm.com> References: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from e23smtp07.au.ibm.com ([202.81.31.140]:58486 "EHLO e23smtp07.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753856AbaCJUgg (ORCPT ); Mon, 10 Mar 2014 16:36:36 -0400 Received: from /spool/local by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 06:36:34 +1000 In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: paulus@samba.org, oleg@redhat.com, rjw@rjwysocki.net, 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, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@ozlabs.org, srivatsa.bhat@linux.vnet.ibm.com, Ingo Molnar , sparclinux@vger.kernel.org, "David S. Miller" "Srivatsa S. Bhat" 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 sysfs code in sparc by using this latter form of callback registration. Cc: Ingo Molnar Cc: sparclinux@vger.kernel.org Acked-by: David S. Miller Signed-off-by: Srivatsa S. Bhat --- arch/sparc/kernel/sysfs.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/sparc/kernel/sysfs.c b/arch/sparc/kernel/sysfs.c index c21c673..a364000 100644 --- a/arch/sparc/kernel/sysfs.c +++ b/arch/sparc/kernel/sysfs.c @@ -300,7 +300,7 @@ static int __init topology_init(void) check_mmu_stats(); - register_cpu_notifier(&sysfs_cpu_nb); + cpu_notifier_register_begin(); for_each_possible_cpu(cpu) { struct cpu *c = &per_cpu(cpu_devices, cpu); @@ -310,6 +310,10 @@ static int __init topology_init(void) register_cpu_online(cpu); } + __register_cpu_notifier(&sysfs_cpu_nb); + + cpu_notifier_register_done(); + return 0; }