Memory barriers in userspace? (Linux, x86-64)
You are looking for the full memory barrier atomic builtins of gcc.
Please note the detail on the reference i gave here says,
The [following] builtins are intended to be compatible with those described in the Intel Itanium Processor-specific Application Binary Interface, section 7.4. As such, they depart from the normal GCC practice of using the “__builtin_” prefix, and further that they are overloaded such that they work on multiple types.
Posix defines a number of functions as acting as memory barriers. Memory locations must not be concurrently accessed; to prevent this, use synchronization - and that synchronization will also work as a barrier.
Use libatomic_ops. http://www.hpl.hp.com/research/linux/atomic_ops/
It's not compiler-specific, and less buggy than the GCC stuff. It's not a giganto-library that provides tons of functionality you don't care about. It just provides atomic operations. Also, it's portable to different CPU architectures.