From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v3 37/52] acpi-cpufreq: Fix CPU hotplug callback registration Date: Tue, 11 Mar 2014 02:10:06 +0530 Message-ID: <20140310204005.10746.58112.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-kernel-owner@vger.kernel.org To: paulus@samba.org, oleg@redhat.com, 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, "Rafael J. Wysocki" , Ingo Molnar , cpufreq@vger.kernel.orglinux-pm@vger.kernel.org, Viresh Kumar "Srivatsa S. Bhat" List-Id: linux-pm@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 acpi-cpufreq code by using this latter form of callback registration. Cc: "Rafael J. Wysocki" Cc: Ingo Molnar Cc: cpufreq@vger.kernel.org Cc: linux-pm@vger.kernel.org Acked-by: Viresh Kumar Signed-off-by: Srivatsa S. Bhat --- drivers/cpufreq/acpi-cpufreq.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c index 18448a7..245ae078e 100644 --- a/drivers/cpufreq/acpi-cpufreq.c +++ b/drivers/cpufreq/acpi-cpufreq.c @@ -907,15 +907,16 @@ static void __init acpi_cpufreq_boost_init(void) acpi_cpufreq_driver.boost_supported = true; acpi_cpufreq_driver.boost_enabled = boost_state(0); - get_online_cpus(); + + cpu_notifier_register_begin(); /* Force all MSRs to the same value */ boost_set_msrs(acpi_cpufreq_driver.boost_enabled, cpu_online_mask); - register_cpu_notifier(&boost_nb); + __register_cpu_notifier(&boost_nb); - put_online_cpus(); + cpu_notifier_register_done(); } }