Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756141AbaBEWS0 (ORCPT ); Wed, 5 Feb 2014 17:18:26 -0500 Received: from e23smtp06.au.ibm.com ([202.81.31.148]:59031 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755263AbaBEWSV (ORCPT ); Wed, 5 Feb 2014 17:18:21 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 46/51] trace, ring-buffer: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org Cc: mingo@kernel.org, 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, srivatsa.bhat@linux.vnet.ibm.com, Steven Rostedt , Frederic Weisbecker , Ingo Molnar , "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:42:58 +0530 Message-ID: <20140205221257.19080.88037.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> References: <20140205220251.19080.92336.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14020522-7014-0000-0000-00000448B6E4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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_maps_update_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_maps_update_done(); Fix the tracing ring-buffer code by using this latter form of callback registration. Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: Ingo Molnar Signed-off-by: Srivatsa S. Bhat --- kernel/trace/ring_buffer.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 294b8a2..ca3eb61 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1301,7 +1301,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, * In that off case, we need to allocate for all possible cpus. */ #ifdef CONFIG_HOTPLUG_CPU - get_online_cpus(); + cpu_maps_update_begin(); cpumask_copy(buffer->cpumask, cpu_online_mask); #else cpumask_copy(buffer->cpumask, cpu_possible_mask); @@ -1324,10 +1324,10 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, #ifdef CONFIG_HOTPLUG_CPU buffer->cpu_notify.notifier_call = rb_cpu_notify; buffer->cpu_notify.priority = 0; - register_cpu_notifier(&buffer->cpu_notify); + __register_cpu_notifier(&buffer->cpu_notify); + cpu_maps_update_done(); #endif - put_online_cpus(); mutex_init(&buffer->mutex); return buffer; @@ -1341,7 +1341,9 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, fail_free_cpumask: free_cpumask_var(buffer->cpumask); - put_online_cpus(); +#ifdef CONFIG_HOTPLUG_CPU + cpu_maps_update_done(); +#endif fail_free_buffer: kfree(buffer); @@ -1358,16 +1360,17 @@ ring_buffer_free(struct ring_buffer *buffer) { int cpu; - get_online_cpus(); - #ifdef CONFIG_HOTPLUG_CPU - unregister_cpu_notifier(&buffer->cpu_notify); + cpu_maps_update_begin(); + __unregister_cpu_notifier(&buffer->cpu_notify); #endif for_each_buffer_cpu(buffer, cpu) rb_free_cpu_buffer(buffer->buffers[cpu]); - put_online_cpus(); +#ifdef CONFIG_HOTPLUG_CPU + cpu_maps_update_done(); +#endif kfree(buffer->buffers); free_cpumask_var(buffer->cpumask); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/