Are Win32 InterlockedIncrement and InterlockedExchange atomic across processes?

Question

MSDN says that the interlocked functions provide a simple mechanism for synchronizing access to a variable that is shared by multiple threads.

I am not sure if they work across threads of multiple processes if the variable is in the shared memory of the processes.

Similarly what about GNU GCC compiler intrinsic: __sync_add_and_fetch and __sync_lock_test_and_set?

Answer 1

This question is essentially two questions for two different answers.

1. For __sync_XXX builtins in GCC answer is yes.

Refer to any online doc like this , where described, that these builtins are normally issuing full barrier, preventing even internal speculating loads inside processor pipeline. Every and all multi-thread, multi-process, etc. shared memory is safe with them.

2. I know nothing about Windows InterLockedXXX functions. But MSDN knows, and says:

The threads of different processes can use this mechanism if the variable is in shared memory

So both answers are "yes".