On Fri, Jan 11, 2019 at 11:28 AM Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > > On 2019/01/11 19:19, Dmitry Vyukov wrote: > >> @@ -200,6 +200,7 @@ void end_buffer_write_sync(struct buffer_head *bh, int uptodate) > >> struct buffer_head *head; > >> struct page *page; > >> int all_mapped = 1; > >> + static unsigned long last; > > > > /\/\/\/\/\/\ > > > > We will have to re-fix this when we start testing with KTSAN, data > > race detector. > > What's wrong? This race is harmless. How did you arrive to the conclusion that it is harmless? There is only one relevant standard covering this, which is the C language standard, and it is very clear on this -- this has Undefined Behavior, that is the same as, for example, reading/writing random pointers. Check out this on how any race that you might think is benign can be badly miscompiled and lead to arbitrary program behavior: https://software.intel.com/en-us/blogs/2013/01/06/benign-data-races-what-could-possibly-go-wrong
