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The trouble with volatile

The trouble with volatile

Posted May 14, 2007 7:16 UTC (Mon) by xoddam (subscriber, #2322)
In reply to: The trouble with volatile by giraffedata
Parent article: The trouble with volatile

Thanks girrafedata -- you have summed up all my niggling doubts about Linus' argument. His sweeping generalisations apply as well to explicit barriers as they do to volatile; they are undoubtedly the best solution to the problems they are used in the Linux kernel to solve, but they are not so much less general that his argument sweeps all before it.

What you don't mention (and Linus does) is that volatile can actually produce incorrect (as well as inefficient) code, because the compiler is not necessarily able to produce the right kind of barrier operation. Compilers know about instruction architectures and, maybe, something about which optimisations work best for which processor families, but they aren't oracles on the most appropriate bus synchronisation operations for every system architecture.


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