I wonder if I could read or write shared int value without locking on mips cpu (especially Amazon or Danube). What I mean is if such a read or write are atomic (other thread can’t interrupt them). To be clear – I don’t want to prevent the race between threads, but I care if int value itself is not corrupted.
Assuming that the compiler aligns all ints at the boundaries of cpu word, it should be possible. I use gcc (g++). Tests also shows that it seems work correctly. But maybe someone knows it for sure?
Use gcc’s builtin atomic operations and you’ll get warnings if they’re not supported: http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html
It looks like combinations of addition/subtraction and testing (at least) are possible on the hardware: http://rswiki.csie.org/lxr/http/source/include/asm-mips/atomic.h