Messages in this thread | | | From | Matt Turner <> | Date | Tue, 14 Jan 2014 09:08:41 -0800 | Subject | Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock() |
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On Tue, Jan 14, 2014 at 3:03 AM, Peter Zijlstra <peterz@infradead.org> wrote: > 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.
That's right, and thanks for the heads-up. Alpha can only address 4 and 8 bytes atomically. (LDL_L, LDQ_L, STL_C, STQ_C).
The Byte-Word extension in EV56 doesn't add new atomics, so in fact no Alphas can address < 4 bytes atomically.
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