ia64, salinfo: Fix 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 salinfo 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>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c
index 960a396f5929..ee9719eebb1e 100644
--- a/arch/ia64/kernel/salinfo.c
+++ b/arch/ia64/kernel/salinfo.c
@@ -635,6 +635,8 @@ salinfo_init(void)
                                            (void *)salinfo_entries[i].feature);
         }
 
+        cpu_notifier_register_begin();
+
         for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) {
                 data = salinfo_data + i;
                 data->type = i;
@@ -669,7 +671,9 @@ salinfo_init(void)
         salinfo_timer.function = &salinfo_timeout;
         add_timer(&salinfo_timer);
 
-        register_hotcpu_notifier(&salinfo_cpu_notifier);
+        __register_hotcpu_notifier(&salinfo_cpu_notifier);
+
+        cpu_notifier_register_done();
 
         return 0;
 }