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scsi, fcoe: 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 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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/scsi/fcoe/fcoe.c
View File

@ -2633,14 +2633,18 @@ static int __init fcoe_init(void)
skb_queue_head_init(&p->fcoe_rx_list); skb_queue_head_init(&p->fcoe_rx_list);
} }
cpu_notifier_register_begin();
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
fcoe_percpu_thread_create(cpu); fcoe_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */ /* Initialize per CPU interrupt thread */
rc = register_hotcpu_notifier(&fcoe_cpu_notifier); rc = __register_hotcpu_notifier(&fcoe_cpu_notifier);
if (rc) if (rc)
goto out_free; goto out_free;
cpu_notifier_register_done();
/* Setup link change notification */ /* Setup link change notification */
fcoe_dev_setup(); fcoe_dev_setup();
@ -2655,6 +2659,9 @@ static int __init fcoe_init(void)
for_each_online_cpu(cpu) { for_each_online_cpu(cpu) {
fcoe_percpu_thread_destroy(cpu); fcoe_percpu_thread_destroy(cpu);
} }
cpu_notifier_register_done();
mutex_unlock(&fcoe_config_mutex); mutex_unlock(&fcoe_config_mutex);
destroy_workqueue(fcoe_wq); destroy_workqueue(fcoe_wq);
return rc; return rc;
@ -2687,11 +2694,15 @@ static void __exit fcoe_exit(void)
} }
rtnl_unlock(); rtnl_unlock();
unregister_hotcpu_notifier(&fcoe_cpu_notifier); cpu_notifier_register_begin();
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
fcoe_percpu_thread_destroy(cpu); fcoe_percpu_thread_destroy(cpu);
__unregister_hotcpu_notifier(&fcoe_cpu_notifier);
cpu_notifier_register_done();
mutex_unlock(&fcoe_config_mutex); mutex_unlock(&fcoe_config_mutex);
/* /*