From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752938AbaBNIAh (ORCPT ); Fri, 14 Feb 2014 03:00:37 -0500 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:38765 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752895AbaBNIAc (ORCPT ); Fri, 14 Feb 2014 03:00:32 -0500 From: "Srivatsa S. Bhat" Subject: [PATCH v2 26/52] x86, hpet: Fix CPU hotplug callback registration To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, 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, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, "Srivatsa S. Bhat" Date: Fri, 14 Feb 2014 13:25:02 +0530 Message-ID: <20140214075501.22701.65312.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.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: 14021408-5564-0000-0000-00000C03E4A8 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_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 hpet code in x86 by using this latter form of callback registration. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/x86/kernel/hpet.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index da85a8e..d89382b 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -943,12 +943,14 @@ static __init int hpet_late_init(void) if (boot_cpu_has(X86_FEATURE_ARAT)) return 0; + cpu_notifier_register_begin(); for_each_online_cpu(cpu) { hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu); } /* This notifier should be called after workqueue is ready */ - hotcpu_notifier(hpet_cpuhp_notify, -20); + __hotcpu_notifier(hpet_cpuhp_notify, -20); + cpu_notifier_register_done(); return 0; } From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v2 26/52] x86, hpet: Fix CPU hotplug callback registration Date: Fri, 14 Feb 2014 13:25:02 +0530 Message-ID: <20140214075501.22701.65312.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: paulus@samba.org, oleg@redhat.com, rusty@rustcorp.com.au, peterz@infradead.org, 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, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org"Srivatsa S. Bhat" List-Id: linux-arch.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_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 hpet code in x86 by using this latter form of callback registration. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/x86/kernel/hpet.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index da85a8e..d89382b 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -943,12 +943,14 @@ static __init int hpet_late_init(void) if (boot_cpu_has(X86_FEATURE_ARAT)) return 0; + cpu_notifier_register_begin(); for_each_online_cpu(cpu) { hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu); } /* This notifier should be called after workqueue is ready */ - hotcpu_notifier(hpet_cpuhp_notify, -20); + __hotcpu_notifier(hpet_cpuhp_notify, -20); + cpu_notifier_register_done(); return 0; } From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp04.in.ibm.com ([122.248.162.4]:38759 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752115AbaBNIAc (ORCPT ); Fri, 14 Feb 2014 03:00:32 -0500 Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 14 Feb 2014 13:30:29 +0530 From: "Srivatsa S. Bhat" Subject: [PATCH v2 26/52] x86, hpet: Fix CPU hotplug callback registration Date: Fri, 14 Feb 2014 13:25:02 +0530 Message-ID: <20140214075501.22701.65312.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> References: <20140214074750.22701.47330.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: paulus@samba.org, oleg@redhat.com, mingo@kernel.org, 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, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, "H. Peter Anvin" , x86@kernel.org"Srivatsa S. Bhat" Message-ID: <20140214075502.gmitUUpnc-Y35jb-NsTZy-fbImBhum_F6nTvG7uKIDc@z> 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 hpet code in x86 by using this latter form of callback registration. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/x86/kernel/hpet.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index da85a8e..d89382b 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -943,12 +943,14 @@ static __init int hpet_late_init(void) if (boot_cpu_has(X86_FEATURE_ARAT)) return 0; + cpu_notifier_register_begin(); for_each_online_cpu(cpu) { hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu); } /* This notifier should be called after workqueue is ready */ - hotcpu_notifier(hpet_cpuhp_notify, -20); + __hotcpu_notifier(hpet_cpuhp_notify, -20); + cpu_notifier_register_done(); return 0; }