On 2020/01/29 21:21, Marco Elver wrote: >> By the way, can READ_ONCE()/WRITE_ONCE() really solve this warning? >> The link above says read/write on the same location ( mm/page_counter.c:129 ). >> I don't know how READ_ONCE()/WRITE_ONCE() can solve the race. > > It avoids the *data* race, with *_ONCE telling the compiler to not > optimize the accesses in concurrency-unfriendly ways. Since *_ONCE is > used, it conveys clear intent that the code here is meant to be > concurrent, and KCSAN stops complaining (and assumes that the *logic* > is correct). I see. Unlike c->failcnt++ which involves read-modify-write, *_ONCE() can be used for simple read (like c->watermark) or simple write (like c->watermark = new) case.
