Messages in this thread | | | Date | Fri, 24 Jun 2016 10:30:28 -0700 | From | Davidlohr Bueso <> | Subject | Re: [PATCH -tip 00/12] locking/atomics: Add and use inc,dec calls for FETCH-OP flavors |
| |
On Fri, 24 Jun 2016, James Bottomley wrote:
>On Mon, 2016-06-20 at 13:05 -0700, Davidlohr Bueso wrote: >> Hi, >> >> The series is really straightforward and based on Peter's work that >> introduces[1] the atomic_fetch_$op machinery. Only patch 1 implements >> the actual atomic_fetch_{inc,dec} calls based on >> atomic_fetch_{add,sub}. > >Could I just ask why? atomic_inc_return(x) - 1 seems a reasonable >thing to do to me.
For one restoring the old state like that can be racy and looses the notion of atomicity. The new family of atomic_fetch_$ops also better express the purpose of the call imo. Finally, the added machinery (considering it came from fetch_op() NOHZ needs), was mainly suggested by Linus (although yes, we don't have users for all the calls): https://lkml.org/lkml/2016/3/15/352.
Thanks, Davidlohr
| |