Messages in this thread | | | Date | Thu, 17 Dec 2020 06:59:55 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [patch 3/3] tick: Annotate tick_do_timer_cpu data races |
| |
On Thu, Dec 17, 2020 at 11:48:23AM +0100, Peter Zijlstra wrote: > On Wed, Dec 16, 2020 at 01:19:31PM -0800, Paul E. McKenney wrote: > > Given that there is no optimization potential, then the main reason to use > > data_race() instead of *_ONCE() is to prevent KCSAN from considering the > > accesses when looking for data races. But that is mostly for debugging > > accesses, in cases when these accesses are not really part of the > > concurrent algorithm. > > > > So if I understand the situation correctly, I would be using *ONCE(). > > Huh, what, why? > > The code doesn't need READ_ONCE(), it merely wants to tell kasan that > the race it observes is fine and as to please shut up. > > IOW data_race() is accurate and right.
Other way around.
The code does not need any of the compiler optimizations that might someday be enabled by data_race(). So why do you need data_race() here? What do exactly is lost by instead using READ_ONCE()?
Thanx, Paul
| |