Re: [RFC][PATCH] mips: Fix arch_spin_unlock()

From: Peter Zijlstra
Date: Thu Nov 12 2015 - 13:00:19 EST

On Thu, Nov 12, 2015 at 09:46:53AM -0800, David Daney wrote:

> For CONFIG_CPU_CAVIUM_OCTEON the proper thing would be:
> smp_wmb();
> smp_rmb();
> Which expands to exactly the same thing as wmb() because smp_rmb() expands
> to nothing.

OK, so the current code isn't broken because for Cavium wmb is suffient
because rmb is a no-op, and for !Cavium wmb expands to SYNC.

> You yourself seem to have added smp_store_release(), so we could even do:
> smp_store_release(&lock->h.serving_now, lock->h.serving_now + 1);
> That would leave us to cook up a proper definition of smp_store_release().

That is indeed the better solution.
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