lkml.org 
[lkml]   [2018]   [Jun]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCHv2 05/16] atomics: prepare for atomic64_fetch_add_unless()
On Tue, Jun 05, 2018 at 11:26:37AM +0200, Peter Zijlstra wrote:
> On Tue, May 29, 2018 at 04:43:35PM +0100, Mark Rutland wrote:
> > /**
> > + * atomic64_add_unless - add unless the number is already a given value
> > + * @v: pointer of type atomic_t
> > + * @a: the amount to add to v...
> > + * @u: ...unless v is equal to u.
> > + *
> > + * Atomically adds @a to @v, so long as @v was not already @u.
> > + * Returns non-zero if @v was not @u, and zero otherwise.
>
> I always get confused by that wording; would something like: "Returns
> true if the addition was done" not be more clear?

Sounds clearer to me; I just stole the wording from the existing
atomic_add_unless().

I guess you'll want similar for the conditional inc/dec ops, e.g.

/**
* atomic_inc_not_zero - increment unless the number is zero
* @v: pointer of type atomic_t
*
* Atomically increments @v by 1, so long as @v is non-zero.
* Returns non-zero if @v was non-zero, and zero otherwise.
*/

> > + */
> > +#ifdef atomic64_fetch_add_unless
> > +static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)
>
> Do we want to make that a "bool' return?

I think so -- that's what the instrumented wrappers (and x86) do today
anyhow, and what I ended up using for the generated headers.

I'll spin a prep patch cleaning up the existing fallbacks in
<linux/atomic.h>, along with the comment fixup above, then rework the
additions likewise.

Thanks,
Mark.

\
 
 \ /
  Last update: 2018-06-05 11:54    [W:0.023 / U:5.152 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site