> On Feb 8, 2020, at 8:44 PM, John Hubbard <jhubbard@xxxxxxxxxx> wrote: > > So it looks like we're probably stuck with having to annotate the code. Given > that, there is a balance between how many macros, and how much commenting. For > example, if there is a single macro (data_race, for example), then we'll need to > add comments for the various cases, explaining which data_race situation is > happening. On the other hand, it is perfect fine of not commenting on each data_race() that most of times, people could run git blame to learn more details. Actually, no maintainers from various of subsystems asked for commenting so far. > > That's still true, but to a lesser extent if more macros are added. In this case, > I suspect that READ_BITS() makes the commenting easier and shorter. So I'd tentatively > lead towards adding it, but what do others on the list think? Even read bits could be dangerous from data races and confusing at best, so I am not really sure what the value of introducing this new macro. People who like to understand it correctly still need to read the commit logs. This flags->zonenum is such a special case that I don’t really see it regularly for the last few weeks digging KCSAN reports, so even if it is worth adding READ_BITS(), there are more equally important macros need to be added together to be useful initially. For example, HARMLESS_COUNTERS(), READ_SINGLE_BIT(), READ_IMMUTATABLE_BITS() etc which Linus said exactly wanted to avoid.
