Messages in this thread | | | From | Catalin Marinas <> | Subject | Re: [PATCH 0/3] Add OMAP hardware spinlock misc driver | Date | Mon, 18 Oct 2010 16:27:05 +0100 |
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Peter Zijlstra <peterz@infradead.org> wrote: > On Mon, 2010-10-18 at 14:35 +0100, Russell King - ARM Linux wrote: >> In any case, Linux's spinlock API (or more accurately, the ARM exclusive >> access instructions) relies upon hardware coherency support (a piece of >> hardware called an exclusive monitor) which isn't present on the M3 nor >> DSP processors. So there's no way to ensure that updates from the M3 >> and DSP are atomic wrt the A9 updates. > > Right, so the problem is that there simply is no way to do atomic memory > access from these auxiliary processing units wrt the main CPU? Seeing as > they operate on the same memory space, wouldn't it make sense to have > them cache-coherent and thus provide atomicy guarantees through that?
With cache coherency you may get atomicity of writes or reads but usually not atomic modifications.
-- Catalin
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