From patchwork Mon Mar 10 20:34:39 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Srivatsa S. 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Bhat" Subject: [PATCH v3 04/52] CPU hotplug, perf: Fix CPU hotplug callback registration 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, Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:04:39 +0530 Message-ID: <20140310203438.10746.24505.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> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14031020-8878-0000-0000-00000B4132B9 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html 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;