Re: [PATCH 2/5] drm/i915: Wrap tasklet_struct for abuse

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Chris Wilson (2018-05-09 15:27:58)
> In the next few patches, we want to abuse tasklet to avoid ksoftirqd
> latency along critical paths. To make that abuse easily to swallow,
> first coat the tasklet in a little syntactic sugar.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c             |  4 +-
>  drivers/gpu/drm/i915/i915_irq.c             |  2 +-
>  drivers/gpu/drm/i915/i915_tasklet.h         | 78 +++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_engine_cs.c      | 11 ++-
>  drivers/gpu/drm/i915/intel_guc_submission.c |  8 +--
>  drivers/gpu/drm/i915/intel_lrc.c            | 18 ++---
>  drivers/gpu/drm/i915/intel_ringbuffer.h     |  3 +-
>  7 files changed, 102 insertions(+), 22 deletions(-)
>  create mode 100644 drivers/gpu/drm/i915/i915_tasklet.h
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 63c96c2b8fcf..59e04387a27c 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3036,7 +3036,7 @@ i915_gem_reset_prepare_engine(struct intel_engine_cs *engine)
>          * Turning off the execlists->tasklet until the reset is over
>          * prevents the race.
>          */
> -       tasklet_disable(&engine->execlists.tasklet);
> +       i915_tasklet_lock(&engine->execlists.tasklet);

Hmm, probably sensible to stick to disable/enable:

 - better match to tasklet_interface (no arbitrary impedance mismatch)

 - they are counting locks rather than mutex which we commonly think of
   for lock/unlock (more like a semaphore).

After dropping the custom flush+disable wrapper, there's no good reason
to have a custom name. Thoughts?
-Chris
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