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SubjectRe: [PATCH 1/3] jump_labels: fix concurrent static_key_enable/disable()
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On 01/08/2017 18:45, Peter Zijlstra wrote:
>
> Thanks for doing these patches, I hadn't come around to them yet.
>
> On Tue, Aug 01, 2017 at 05:24:04PM +0200, Paolo Bonzini wrote:
>>
>> +void static_key_enable(struct static_key *key)
>> +{
>> + STATIC_KEY_CHECK_USE();
>> + if (atomic_read(&key->enabled) > 0) {
>> + WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
>> + return;
>> + }
>> +
>> + cpus_read_lock();
>> + jump_label_lock();
>> + if (atomic_read(&key->enabled) == 0) {
>> + atomic_set(&key->enabled, -1);
>> + jump_label_update(key);
>
> As per the previous discussion, should I do a patch adding barriers here
> (or using atomic_set_release()) such that we close the window where a
> concurrent inc/enable sees 1 but not all text changes?

Sure, and that applies to static_key_slow_inc as well.

Paolo

>> + atomic_set(&key->enabled, 1);
>> + }
>> + jump_label_unlock();
>> + cpus_read_unlock();
>> +}
>> +EXPORT_SYMBOL_GPL(static_key_enable);

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