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scsi, bnx2fc: 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 bnx2fc code in scsi by using this latter form of callback
registration.

Cc: Eddie Wai <eddie.wai@broadcom.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 02:09:45 +05:30 committed by Rafael J. Wysocki
parent bc0003c93f
commit 7229b6d0b2
1 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/scsi/bnx2fc/bnx2fc_fcoe.c
View File

@ -2586,12 +2586,16 @@ static int __init bnx2fc_mod_init(void)
spin_lock_init(&p->fp_work_lock);
}
cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
bnx2fc_percpu_thread_create(cpu);
}
/* Initialize per CPU interrupt thread */
register_hotcpu_notifier(&bnx2fc_cpu_notifier);
__register_hotcpu_notifier(&bnx2fc_cpu_notifier);
cpu_notifier_register_done();
cnic_register_driver(CNIC_ULP_FCOE, &bnx2fc_cnic_cb);
@ -2656,13 +2660,17 @@ static void __exit bnx2fc_mod_exit(void)
if (l2_thread)
kthread_stop(l2_thread);
unregister_hotcpu_notifier(&bnx2fc_cpu_notifier);
cpu_notifier_register_begin();
/* Destroy per cpu threads */
for_each_online_cpu(cpu) {
bnx2fc_percpu_thread_destroy(cpu);
}
__unregister_hotcpu_notifier(&bnx2fc_cpu_notifier);
cpu_notifier_register_done();
destroy_workqueue(bnx2fc_wq);
/*
* detach from scsi transport