Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755925AbaBEWQL (ORCPT ); Wed, 5 Feb 2014 17:16:11 -0500 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:57715 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754472AbaBEWQG (ORCPT ); Wed, 5 Feb 2014 17:16:06 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH 34/51] zsmalloc: 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, Minchan Kim , Nitin Gupta , linux-mm@kvack.org, "Srivatsa S. Bhat" Date: Thu, 06 Feb 2014 03:40:43 +0530 Message-ID: <20140205221043.19080.20246.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: 14020522-2000-0000-0000-00000F986AFA 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 zsmalloc code by using this latter form of callback registration. Cc: Minchan Kim Cc: Nitin Gupta Cc: linux-mm@kvack.org Signed-off-by: Srivatsa S. Bhat --- mm/zsmalloc.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index c03ca5e..6f7364c 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -814,21 +814,32 @@ static void zs_exit(void) { int cpu; + cpu_maps_update_begin(); + for_each_online_cpu(cpu) zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu); - unregister_cpu_notifier(&zs_cpu_nb); + __unregister_cpu_notifier(&zs_cpu_nb); + + cpu_maps_update_done(); } static int zs_init(void) { int cpu, ret; - register_cpu_notifier(&zs_cpu_nb); + cpu_maps_update_begin(); + + __register_cpu_notifier(&zs_cpu_nb); for_each_online_cpu(cpu) { ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu); - if (notifier_to_errno(ret)) + if (notifier_to_errno(ret)) { + cpu_maps_update_done(); goto fail; + } } + + cpu_maps_update_done(); + return 0; fail: zs_exit(); -- 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/