On 07/06/2018 10:42, Viresh Kumar wrote: > On 07-06-18, 10:32, Peter Zijlstra wrote: >> On Thu, Jun 07, 2018 at 10:18:27AM +0200, Daniel Lezcano wrote: >>> So IIUC, neither atomic or WRITE|READ_ONCE are necessary in this code >>> because of the wake_up_process() barrier is enough, right ? >> >> I didn't look hard enough; if there ever is a time where the loads and >> stores happen concurrently, you need READ/WRITE_ONCE(). If there is no >> concurrency on the variables, you don't need anything. >> >> Neither atomic_read/set() nor REAd/WRITE_ONCE() will help with ordering, >> which is what the wake_up_process() would provide here, different things >> entirely. > > Right and you still need the READ/WRITE_ONCE() thing as > idle_injection_set_duration() may run in parallel with the idle_injection_fn() > thread. > > And I don't think the purpose of atomic_read/write was ever to take care of > the > ordering issues in this code, it was always about parallel loads/stores.
Yes, correct. But if we don't care about who wins to store to value, is there a risk of scramble variable if we just assign a value ? -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
