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: In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> Sender: linux-pm-owner@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" List-Id: linux-arch.vger.kernel.org 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; } From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp07.au.ibm.com ([202.81.31.140]:58484 "EHLO e23smtp07.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752845AbaCJUgg (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 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> In-Reply-To: <20140310203312.10746.310.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 Sender: linux-arch-owner@vger.kernel.org List-ID: To: 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 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, sparclinux@vger.kernel.org, "David S. Miller" "Srivatsa S. Bhat" Message-ID: <20140310203609.DbKaXY5lcn4lloI7a74_7OpTSmrMIj0v-OXq8KHtA-w@z> 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; }