On Tue, 12 Nov 2019, Linus Torvalds wrote: > Honestly, my preferred model would have been to just add a comment, > and have the reporting tool know to then just ignore it. So something > like > > + // Benign data-race on min_flt > tsk->min_flt++; > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); > > for the case that Eric mentioned - the tool would trigger on > "data-race", and the rest of the comment could/should be for humans. > Without making the code uglier, but giving the potential for a nice > leghibl.e explanation instead of a completely illegible "let's > randomly use WRITE_ONCE() here" or something like that. Just to be perfectly clear, then: Your feeling is that we don't need to tell the compiler anything at all about these races, because if a compiler generates code that is non-robust against such things then you don't want to use it for the kernel. And as a corollary, the only changes you want to make to the source code are things that tell KCSAN not to worry about these races when they occur. Right? > + // Benign data-race on min_flt > tsk->min_flt++; > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); I suggest grouping the accesses into classes somehow, and telling KCSAN that races between accesses in the same class are okay but racing accesses in different classes should trigger a warning. That would give the tool a better chance of finding genuine races. Alan Stern
