There are many types of barriers depending on the processor architecture. They're usually used in pairs so for example a read barrier would be used when mutex i

There are many types of barriers depending on the processor architecture. They're usually used in pairs so for example a read barrier would be used when mutex is acquired and the a write barrier when it's released. If the compiler is smart about its memory barrier intrinsics it will make sure to reread anything after the read barrier and write everything before the write barrier. This will speed things up by not having to use volatile. Between the barriers it can cache reads and inside registers and optimize out multiple writes like normal. If the compiler can't do that then you need to use volatile. Volatile was meant for I/O where every read has to hit the bus. So if you're forced to use it then you just copy the volatile variable into a non volatile one for use inside your mutex to get some speed back.