On 2014-03-20 1:52 PM, Steven Schveighoffer wrote:
On Thu, 20 Mar 2014 13:43:58 -0400, Etienne <etci...@gmail.com> wrote:
I'd like to "cowboy it" on an AA that looks like this:
__gshared bool[string] m_mutex;
I think it'll be much faster for my code because this AA could need to
be checked and switched possibly millions of times per second and I
wouldn't want to slow it down with a mutex protecting it.
I'm thinking the bool would be synchronized at the hardware level
anyway, since it's just a bit being flipped or returned. Am I right to
assume this and (maybe an assembly guru can answer) it safe to use?
No, it's not safe. With memory reordering, there is no "safe" unless you
use mutexes or low-level atomics.
Long story short, the compiler, the processor, or the memory cache can
effectively reorder operations, making one thread see things happen in a
different order than they are written/executed on another thread. There
are no guarantees.
-Steve
Right, I was assuming it was always ordered, but modern processor
pipelines are different I guess.
