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@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: linux-ia64@xxxxxxxxxxxxxxx
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---
arch/ia64/kernel/salinfo.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c
index 960a396..ee9719e 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;
}
--
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