From e12b711196a158a475350ee67876a1e9e2601661 Mon Sep 17 00:00:00 2001 From: Srivatsa S. Bhat Date: Tue, 11 Mar 2014 02:10:12 +0530 Subject: drivers/base/topology.c: Fix CPU hotplug callback registration 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 topology code by using this latter form of callback registration. Cc: Ingo Molnar Acked-by: Greg Kroah-Hartman Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- drivers/base/topology.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'drivers/base') diff --git a/drivers/base/topology.c b/drivers/base/topology.c index 94ffee378f10..a738d1069d6b 100644 --- a/drivers/base/topology.c +++ b/drivers/base/topology.c @@ -161,16 +161,20 @@ static int topology_cpu_callback(struct notifier_block *nfb, static int topology_sysfs_init(void) { int cpu; - int rc; + int rc = 0; + + cpu_notifier_register_begin(); for_each_online_cpu(cpu) { rc = topology_add_dev(cpu); if (rc) - return rc; + goto out; } - hotcpu_notifier(topology_cpu_callback, 0); + __hotcpu_notifier(topology_cpu_callback, 0); - return 0; +out: + cpu_notifier_register_done(); + return rc; } device_initcall(topology_sysfs_init); -- cgit v1.2.3