linux-kernel - Re: [PATCH] drm/i915/pmu: Use local64_try_cmpxchg in i915_pmu_event

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Date:   Tue, 4 Jul 2023 11:25:15 +0200
From:   Uros Bizjak <ubizjak@...il.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/i915/pmu: Use local64_try_cmpxchg in i915_pmu_event_read

On Tue, Jul 4, 2023 at 10:37 AM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
>
> On Tue, 04 Jul 2023, Uros Bizjak <ubizjak@...il.com> wrote:
> > On Tue, Jul 4, 2023 at 9:28 AM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
> >> You could save everyone a lot of time by actually documenting what these
> >> functions do. Assume you don't know what local64_try_cmpxchg() does, and
> >> see how many calls you have to go through to figure it out.
> >
> > These functions are documented in Documentation/atomic_t.txt (under
> > "RMW ops:" section), and the difference is explained in a separate
> > section "CMPXCHG vs TRY_CMPXCGS" in the same file.
>
> Thanks, but *sigh*.
>
> No kernel-doc above the functions, not even a regular comment
> referencing atomic_t.txt.
>
> $ git grep local.*_try -- Documentation
> [nothing]

Unfortunately, this was always the state w.r.t. local.* atomic
functions. There is an effort to improve the documentation of atomics,
perhaps it will be also extended to local variants.

Uros.