| From | "Srivatsa S. Bhat" <> | Subject | [PATCH 10/51] s390, cacheinfo: Fix CPU hotplug callback registration | Date | Thu, 06 Feb 2014 03:36:23 +0530 |
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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_maps_update_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_maps_update_done();
Fix the cacheinfo code in s390 by using this latter form of callback registration.
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: linux-s390@vger.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> ---
arch/s390/kernel/cache.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/cache.c b/arch/s390/kernel/cache.c index 3a414c0..075af62 100644 --- a/arch/s390/kernel/cache.c +++ b/arch/s390/kernel/cache.c @@ -378,9 +378,12 @@ static int __init cache_init(void) if (!test_facility(34)) return 0; cache_build_info(); + + cpu_maps_update_begin(); for_each_online_cpu(cpu) cache_add_cpu(cpu); - hotcpu_notifier(cache_hotplug, 0); + __hotcpu_notifier(cache_hotplug, 0); + cpu_maps_update_done(); return 0; } device_initcall(cache_init);
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