From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp04.in.ibm.com (e28smtp04.in.ibm.com [122.248.162.4]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id C606A2C00FE for ; Tue, 11 Mar 2014 07:34:52 +1100 (EST) Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 02:04:48 +0530 Received: from d28relay03.in.ibm.com (d28relay03.in.ibm.com [9.184.220.60]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id E2CB8125803E for ; Tue, 11 Mar 2014 02:06:58 +0530 (IST) Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKYgM810158490 for ; Tue, 11 Mar 2014 02:04:42 +0530 Received: from d28av05.in.ibm.com (localhost [127.0.0.1]) by d28av05.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKYiWh017649 for ; Tue, 11 Mar 2014 02:04:45 +0530 From: "Srivatsa S. 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 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> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: linux-arch@vger.kernel.org, ego@linux.vnet.ibm.com, walken@google.com, linux@arm.linux.org.uk, Arnaldo Carvalho de Melo , linux-pm@vger.kernel.org, Peter Zijlstra , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Paul Mackerras , "Srivatsa S. Bhat" , tj@kernel.org, paulmck@linux.vnet.ibm.com, Ingo Molnar List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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;