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 code in net/core/flow.c by using this latter form of callback registration. Cc: Li RongQing <roy.qing...@gmail.com> Cc: Sasha Levin <sasha.le...@oracle.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Chris Metcalf <cmetc...@tilera.com> Cc: Ingo Molnar <mi...@kernel.org> Cc: net...@vger.kernel.org Signed-off-by: David S. Miller <da...@davemloft.net> Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> --- net/core/flow.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/core/flow.c b/net/core/flow.c index dfa602c..9a2151f 100644 --- a/net/core/flow.c +++ b/net/core/flow.c @@ -456,6 +456,8 @@ static int __init flow_cache_init(struct flow_cache *fc) if (!fc->percpu) return -ENOMEM; + cpu_notifier_register_begin(); + for_each_online_cpu(i) { if (flow_cache_cpu_prepare(fc, i)) goto err; @@ -463,7 +465,9 @@ static int __init flow_cache_init(struct flow_cache *fc) fc->hotcpu_notifier = (struct notifier_block){ .notifier_call = flow_cache_cpu, }; - register_hotcpu_notifier(&fc->hotcpu_notifier); + __register_hotcpu_notifier(&fc->hotcpu_notifier); + + cpu_notifier_register_done(); setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd, (unsigned long) fc); @@ -479,6 +483,8 @@ err: fcp->hash_table = NULL; } + cpu_notifier_register_done(); + free_percpu(fc->percpu); fc->percpu = NULL; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/