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scsi, bnx2i: 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 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>
This commit is contained in:
Srivatsa S. Bhat 2014-03-11 02:09:39 +05:30 committed by Rafael J. Wysocki
parent 009f225ef0
commit bc0003c93f
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/bnx2i/bnx2i_init.c
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@ -537,11 +537,15 @@ static int __init bnx2i_mod_init(void)
p->iothread = NULL; p->iothread = NULL;
} }
cpu_notifier_register_begin();
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
bnx2i_percpu_thread_create(cpu); bnx2i_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */ /* Initialize per CPU interrupt thread */
register_hotcpu_notifier(&bnx2i_cpu_notifier); __register_hotcpu_notifier(&bnx2i_cpu_notifier);
cpu_notifier_register_done();
return 0; return 0;
@ -581,11 +585,15 @@ static void __exit bnx2i_mod_exit(void)
} }
mutex_unlock(&bnx2i_dev_lock); mutex_unlock(&bnx2i_dev_lock);
unregister_hotcpu_notifier(&bnx2i_cpu_notifier); cpu_notifier_register_begin();
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
bnx2i_percpu_thread_destroy(cpu); bnx2i_percpu_thread_destroy(cpu);
__unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
cpu_notifier_register_done();
iscsi_unregister_transport(&bnx2i_iscsi_transport); iscsi_unregister_transport(&bnx2i_iscsi_transport);
cnic_unregister_driver(CNIC_ULP_ISCSI); cnic_unregister_driver(CNIC_ULP_ISCSI);
} }