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scsi, fcoe: Fix CPU hotplug callback registration

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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 fcoe code in scsi by using this latter form of callback registration.

Cc: Robert Love <robert.w.love@intel.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srivatsa S. Bhat 2014-03-11 02:09:52 +05:30 committed by Rafael J. Wysocki
parent 7229b6d0b2
commit cd45ae3803
1 changed files with 13 additions and 2 deletions
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15
drivers/scsi/fcoe/fcoe.c
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@ -2633,14 +2633,18 @@ static int __init fcoe_init(void)
skb_queue_head_init(&p->fcoe_rx_list);
}
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
fcoe_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */
rc = register_hotcpu_notifier(&fcoe_cpu_notifier);
rc = __register_hotcpu_notifier(&fcoe_cpu_notifier);
if (rc)
goto out_free;
cpu_notifier_register_done();
/* Setup link change notification */
fcoe_dev_setup();
@ -2655,6 +2659,9 @@ out_free:
for_each_online_cpu(cpu) {
fcoe_percpu_thread_destroy(cpu);
}
cpu_notifier_register_done();
mutex_unlock(&fcoe_config_mutex);
destroy_workqueue(fcoe_wq);
return rc;
@ -2687,11 +2694,15 @@ static void __exit fcoe_exit(void)
}
rtnl_unlock();
unregister_hotcpu_notifier(&fcoe_cpu_notifier);
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
fcoe_percpu_thread_destroy(cpu);
__unregister_hotcpu_notifier(&fcoe_cpu_notifier);
cpu_notifier_register_done();
mutex_unlock(&fcoe_config_mutex);
/*