From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp08.in.ibm.com (e28smtp08.in.ibm.com [122.248.162.8]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id C1A452C0242 for ; Tue, 11 Mar 2014 07:36:42 +1100 (EST) Received: from /spool/local by e28smtp08.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Mar 2014 02:06:41 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id 518D4E003F for ; Tue, 11 Mar 2014 02:10:23 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s2AKaZuq61603946 for ; Tue, 11 Mar 2014 02:06:35 +0530 Received: from d28av04.in.ibm.com (localhost [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s2AKaaGH005016 for ; Tue, 11 Mar 2014 02:06:38 +0530 From: "Srivatsa S. Bhat" Subject: [PATCH v3 14/52] powerpc, sysfs: 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 02:06:31 +0530 Message-ID: <20140310203630.10746.99418.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, linux-pm@vger.kernel.org, Olof Johansson , linux-kernel@vger.kernel.org, Wang Dongsheng , linuxppc-dev@ozlabs.org, Madhavan Srinivasan , Paul Mackerras , "Srivatsa S. Bhat" , tj@kernel.org, paulmck@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, 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 sysfs code in powerpc by using this latter form of callback registration. Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Olof Johansson Cc: Wang Dongsheng Cc: Ingo Molnar Cc: linuxppc-dev@lists.ozlabs.org Acked-by: Madhavan Srinivasan Signed-off-by: Srivatsa S. Bhat --- arch/powerpc/kernel/sysfs.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index 97e1dc9..d90d4b7 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -975,7 +975,8 @@ static int __init topology_init(void) int cpu; register_nodes(); - register_cpu_notifier(&sysfs_cpu_nb); + + cpu_notifier_register_begin(); for_each_possible_cpu(cpu) { struct cpu *c = &per_cpu(cpu_devices, cpu); @@ -999,6 +1000,11 @@ static int __init topology_init(void) if (cpu_online(cpu)) register_cpu_online(cpu); } + + __register_cpu_notifier(&sysfs_cpu_nb); + + cpu_notifier_register_done(); + #ifdef CONFIG_PPC64 sysfs_create_dscr_default(); #endif /* CONFIG_PPC64 */