From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: [PATCH v3 08/52] ia64, err-inject: Fix CPU hotplug callback registration Date: Tue, 11 Mar 2014 02:05:10 +0530 Message-ID: <20140310203510.10746.62381.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" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140310203312.10746.310.stgit@srivatsabhat.in.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: paulus@samba.org, oleg@redhat.com, rjw@rjwysocki.net, 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, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@ozlabs.org, srivatsa.bhat@linux.vnet.ibm.com, Tony Luck , Fenghua Yu , Ingo Molnar , linux-ia64@vger.kernel.org"Srivatsa S. Bhat" List-Id: linux-pm@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 error injection code in ia64 by using this latter form of callback registration. Cc: Tony Luck Cc: Fenghua Yu Cc: Ingo Molnar Cc: linux-ia64@vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- arch/ia64/kernel/err_inject.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/ia64/kernel/err_inject.c b/arch/ia64/kernel/err_inject.c index f59c0b8..0c161ed 100644 --- a/arch/ia64/kernel/err_inject.c +++ b/arch/ia64/kernel/err_inject.c @@ -269,12 +269,17 @@ err_inject_init(void) #ifdef ERR_INJ_DEBUG printk(KERN_INFO "Enter error injection driver.\n"); #endif + + cpu_notifier_register_begin(); + for_each_online_cpu(i) { err_inject_cpu_callback(&err_inject_cpu_notifier, CPU_ONLINE, (void *)(long)i); } - register_hotcpu_notifier(&err_inject_cpu_notifier); + __register_hotcpu_notifier(&err_inject_cpu_notifier); + + cpu_notifier_register_done(); return 0; } @@ -288,11 +293,17 @@ err_inject_exit(void) #ifdef ERR_INJ_DEBUG printk(KERN_INFO "Exit error injection driver.\n"); #endif + + cpu_notifier_register_begin(); + for_each_online_cpu(i) { sys_dev = get_cpu_device(i); sysfs_remove_group(&sys_dev->kobj, &err_inject_attr_group); } - unregister_hotcpu_notifier(&err_inject_cpu_notifier); + + __unregister_hotcpu_notifier(&err_inject_cpu_notifier); + + cpu_notifier_register_done(); } module_init(err_inject_init);