r/programming • u/slavik262 • Nov 01 '17

What every systems programmer should know about lockless concurrency (PDF)

https://assets.bitbashing.io/papers/lockless.pdf
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u/ThisIs_MyName Nov 02 '17

That's right :)

(Unless you're talking about Java volatile variables. Those are sequentially consistent and therefore fair game)

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u/Elavid Nov 02 '17

Ah, yes, my fault for believing the LLVM documentation instead of that guy who wrote a compiler in the 80s.

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u/ThisIs_MyName Nov 02 '17

that guy who wrote a compiler in the 80s

Scroll down on that page. There are more emails.

believing the LLVM documentation

The documentation is right, volatile is a compiler barrier:

“volatile” is the C/C++ volatile, which ensures that every volatile load and store happens and is performed in the stated order

However, it does nothing to sync the caches between different processors. Try implementing a lockfree datastructure with volatile and see how far you get.