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 vmstat code in the MM subsystem by using this latter form of callback
registration.
Cc: Andrew Morton <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Cody P Schafer <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Christoph Lameter <[email protected]>
Reviewed-by: Yasuaki Ishimatsu <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
mm/vmstat.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 7249614..12a553e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1290,14 +1290,14 @@ static int __init setup_vmstat(void)
#ifdef CONFIG_SMP
int cpu;
- register_cpu_notifier(&vmstat_notifier);
+ cpu_notifier_register_begin();
+ __register_cpu_notifier(&vmstat_notifier);
- get_online_cpus();
for_each_online_cpu(cpu) {
start_cpu_timer(cpu);
node_set_state(cpu_to_node(cpu), N_CPU);
}
- put_online_cpus();
+ cpu_notifier_register_done();
#endif
#ifdef CONFIG_PROC_FS
proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
--
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