scsi, bnx2i: 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 bnx2i 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>

diff --git a/drivers/scsi/bnx2i/bnx2i_init.c b/drivers/scsi/bnx2i/bnx2i_init.c
index 34c294b42c84e0353d4049737a72c9d3b57dc61a..80c03b452d61960cbe3df5d198fc409e7c49a9e9 100644 (file)
--- a/drivers/scsi/bnx2i/bnx2i_init.c
+++ b/drivers/scsi/bnx2i/bnx2i_init.c
@@ -537,11 +537,15 @@ static int __init bnx2i_mod_init(void)
                p->iothread = NULL;
        }
 
+       cpu_notifier_register_begin();
+
        for_each_online_cpu(cpu)
                bnx2i_percpu_thread_create(cpu);
 
        /* Initialize per CPU interrupt thread */
-       register_hotcpu_notifier(&bnx2i_cpu_notifier);
+       __register_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+       cpu_notifier_register_done();
 
        return 0;
 
@@ -581,11 +585,15 @@ static void __exit bnx2i_mod_exit(void)
        }
        mutex_unlock(&bnx2i_dev_lock);
 
-       unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+       cpu_notifier_register_begin();
 
        for_each_online_cpu(cpu)
                bnx2i_percpu_thread_destroy(cpu);
 
+       __unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+       cpu_notifier_register_done();
+
        iscsi_unregister_transport(&bnx2i_iscsi_transport);
        cnic_unregister_driver(CNIC_ULP_ISCSI);
 }