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ia64, err-inject: 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 error injection code in ia64 by using this latter form of callback
registration.

Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.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 02:05:10 +05:30 committed by Rafael J. Wysocki
parent f5a7d445ff
commit f2e48a8905
1 changed files with 13 additions and 2 deletions
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15
arch/ia64/kernel/err_inject.c
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@ -269,12 +269,17 @@ err_inject_init(void)
#ifdef ERR_INJ_DEBUG
printk(KERN_INFO "Enter error injection driver.\n");
#endif
cpu_notifier_register_begin();
for_each_online_cpu(i) {
err_inject_cpu_callback(&err_inject_cpu_notifier, CPU_ONLINE,
(void *)(long)i);
}
register_hotcpu_notifier(&err_inject_cpu_notifier);
__register_hotcpu_notifier(&err_inject_cpu_notifier);
cpu_notifier_register_done();
return 0;
}
@ -288,11 +293,17 @@ err_inject_exit(void)
#ifdef ERR_INJ_DEBUG
printk(KERN_INFO "Exit error injection driver.\n");
#endif
cpu_notifier_register_begin();
for_each_online_cpu(i) {
sys_dev = get_cpu_device(i);
sysfs_remove_group(&sys_dev->kobj, &err_inject_attr_group);
}
unregister_hotcpu_notifier(&err_inject_cpu_notifier);
__unregister_hotcpu_notifier(&err_inject_cpu_notifier);
cpu_notifier_register_done();
}
module_init(err_inject_init);