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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2014-03-11 02:04:52 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-03-20 13:43:40 +0100
commit9f37bca9a9e97fcd7589492aba7b8a5310026c47 (patch)
treecc985a7fd6fd796e212abd1378fa0fbb59426d61
parenteff722b06bdd6de326894ea2353ec0eda3e5ed34 (diff)
ia64, palinfo: 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 palinfo 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>
-rw-r--r--arch/ia64/kernel/palinfo.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/ia64/kernel/palinfo.c b/arch/ia64/kernel/palinfo.c
index ab333284f4b2..c39c3cd3ac34 100644
--- a/arch/ia64/kernel/palinfo.c
+++ b/arch/ia64/kernel/palinfo.c
@@ -996,13 +996,17 @@ palinfo_init(void)
if (!palinfo_dir)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
/* Create palinfo dirs in /proc for all online cpus */
for_each_online_cpu(i) {
create_palinfo_proc_entries(i);
}
/* Register for future delivery via notify registration */
- register_hotcpu_notifier(&palinfo_cpu_notifier);
+ __register_hotcpu_notifier(&palinfo_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}