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There are cpumask_test_and_clear_cpu/cpumask_setall() APIs, it seems > that API cpumask_setall() does not support atomic operation. > > Do you think it is reasonable to add new API similar with cpumask_setall() > which supports atomic operation? Maybe reasonable, but it's impossible. cpumask is a bitmap, which in turn is an array of unsigned longs. There's no atomic operations on arrays. Thanks, Yury