Comment 3 for bug 1764595

The C11/C++11 atomic support on gcc for embedded ARM is almost completely broken - it is worse than useless because it silently gives incorrect code. For simple read or write access to 32-bit or smaller atomics, the code is correct but inefficient (you don't need DSB and similar barriers on single-core Cortex-M devices). For anything bigger or more complex, you get non-atomic sequences or calls to library functions that have spin locks that cannot work on a single core device.