Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock()

From: Peter Zijlstra
Date: Tue Jan 14 2014 - 06:03:28 EST


On Tue, Jan 14, 2014 at 10:28:23AM +0800, Daniel J Blueman wrote:
> >Peter,
> >
> >I found out that the build failure was caused by the fact that the
> >__native_word() macro (used internally by compiletime_assert_atomic())
> >allows only a size of 4 or 8 for x86-64. The data type that I used is a
> >byte. Is there a reason why byte and short are not considered native?
>
> It seems likely it was implemented like that since there was no existing
> need; long can be relied on as the largest native type, so this should
> suffice and works here:

There's Alphas that cannot actually atomically adres a byte; I do not
konw if Linux cares about them, but if it does, we cannot in fact rely
on this in generic primitives like this.
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