On Tue, 27 Nov 2018 at 12:01, Andrea Parri <andrea.pa...@amarulasolutions.com> wrote: > > Concerning the comment associated to the atomic_fetch_andnot() in > nohz_idle_balance(), Vincent explains [1]: > > "[...] the comment is useless and can be removed [...] it was > referring to a line code above the comment that was present in > a previous iteration of the patchset. This line disappeared in > final version but the comment has stayed." > > So remove the comment. > > Vincent also points out that the full ordering associated to the > atomic_fetch_andnot() primitive could be relaxed, but this patch > insists on the current more conservative/fully ordered solution: > > "Performance" isn't a concern, stay away from "correctness"/subtle > relaxed (re)ordering if possible..., just make sure not to confuse > the next reader with misleading/out-of-date comments. > > [1] > http://lkml.kernel.org/r/cakftptbja-ocbrko6__npqwl3+hljzk7riccpu1r7ydo-ep...@mail.gmail.com > > Suggested-by: Vincent Guittot <vincent.guit...@linaro.org> > Signed-off-by: Andrea Parri <andrea.pa...@amarulasolutions.com> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Vincent Guittot <vincent.guit...@linaro.org>
Looks good to me > --- > kernel/sched/fair.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ac855b2f47746..db514993565b2 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -9533,9 +9533,7 @@ static bool nohz_idle_balance(struct rq *this_rq, enum > cpu_idle_type idle) > return false; > } > > - /* > - * barrier, pairs with nohz_balance_enter_idle(), ensures ... > - */ > + /* could be _relaxed() */ > flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu)); > if (!(flags & NOHZ_KICK_MASK)) > return false; > -- > 2.17.1 >
