> On Feb 9, 2020, at 9:20 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > Using data_race() here seems misleading - there is no race, but we're > using data_race() to suppress a false positive warning from KCSAN, yes? It is a data race in the sense of compilers, i.e., KCSAN is a compiler instrumentation, so here the load and store are both in word-size, but code here is only interested in 3 bits which are never changed. Thus, it is a harmless data race. Marco also mentioned, “Various options were considered, and based on feedback from Linus, decided 'data_race(..)' is the best option:” lore.kernel.org/linux-fsdevel/CAHk-=wg5CkOEF8DTez1Qu0XTEFw_oHhxN98bDnFqbY7HL5AB2g@xxxxxxxxxxxxxx/ Paul also said, ”People will get used to the name more quickly than they will get used to typing the extra seven characters. Here is the current comment header: /* * data_race(): macro to document that accesses in an expression may conflict with * other concurrent accesses resulting in data races, but the resulting * behaviour is deemed safe regardless. * * This macro *does not* affect normal code generation, but is a hint to tooling * that data races here should be ignored. */ I will be converting this to docbook form. In addition, in the KCSAN documentation: * KCSAN understands the ``data_race(expr)`` annotation, which tells KCSAN that any data races due to accesses in ``expr`` should be ignored and resulting behaviour when encountering a data race is deemed safe.”
