On 12/12, Srivatsa S. Bhat wrote: > > On 12/12/2012 10:54 PM, Oleg Nesterov wrote: > > > And when I look at get_online_cpus_atomic() again it uses rmb(). This > > doesn't look correct, we need the full barrier between this_cpu_inc() > > and writer_active(). > > Hmm.. > > > At the same time reader_nested_percpu() can be checked before mb(). > > I thought that since the increment and the check (reader_nested_percpu) > act on the same memory location, they will naturally be run in the given > order, without any need for barriers. Am I wrong?
And this is what I meant, you do not need a barrier before reader_nested_percpu(). But you need to ensure that WRITE(reader_percpu_refcnt) and READ(writer_signal) can't be reordered, so you need mb() in between. rmb() can serialize LOADs and STOREs. Or I misunderstood? Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
