From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v3 04/52] CPU hotplug, perf: Fix CPU hotplug callback registration Date: Tue, 11 Mar 2014 02:04:39 +0530 Message-ID: <20140310203438.10746.24505.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: oleg@redhat.com, rjw@rjwysocki.net, rusty@rustcorp.com.au, 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, Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo "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 perf subsystem's hotplug notifier by using this latter form of callback registration. Also provide a bare-bones version of perf_cpu_notifier() that doesn't invoke the notifiers for the already online CPUs. This would be useful for subsystems that need to perform a different set of initialization for the already online CPUs, or don't need the initialization altogether. Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Signed-off-by: Srivatsa S. Bhat --- include/linux/perf_event.h | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index e56b07f..3356abc 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -835,6 +835,8 @@ do { \ { .notifier_call = fn, .priority = CPU_PRI_PERF }; \ unsigned long cpu = smp_processor_id(); \ unsigned long flags; \ + \ + cpu_notifier_register_begin(); \ fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE, \ (void *)(unsigned long)cpu); \ local_irq_save(flags); \ @@ -843,9 +845,21 @@ do { \ local_irq_restore(flags); \ fn(&fn##_nb, (unsigned long)CPU_ONLINE, \ (void *)(unsigned long)cpu); \ - register_cpu_notifier(&fn##_nb); \ + __register_cpu_notifier(&fn##_nb); \ + cpu_notifier_register_done(); \ } while (0) +/* + * Bare-bones version of perf_cpu_notifier(), which doesn't invoke the + * callback for already online CPUs. + */ +#define __perf_cpu_notifier(fn) \ +do { \ + static struct notifier_block fn##_nb = \ + { .notifier_call = fn, .priority = CPU_PRI_PERF }; \ + \ + __register_cpu_notifier(&fn##_nb); \ +} while (0) struct perf_pmu_events_attr { struct device_attribute attr;