Re: [Intel-gfx] [PATCH v4 03/12] drm/i915: Introduce a ww transaction helper

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 15-06-2021 om 15:14 schreef Thomas Hellström:
> Introduce a for_i915_gem_ww(){} utility to help make the code
> around a ww transaction more readable.
>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_ww.h | 31 +++++++++++++++++++++++++++++-
>  1 file changed, 30 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h b/drivers/gpu/drm/i915/i915_gem_ww.h
> index f2d8769e4118..f6b1a796667b 100644
> --- a/drivers/gpu/drm/i915/i915_gem_ww.h
> +++ b/drivers/gpu/drm/i915/i915_gem_ww.h
> @@ -11,11 +11,40 @@ struct i915_gem_ww_ctx {
>  	struct ww_acquire_ctx ctx;
>  	struct list_head obj_list;
>  	struct drm_i915_gem_object *contended;
> -	bool intr;
> +	unsigned short intr;
> +	unsigned short loop;
>  };
>  
>  void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
>  void i915_gem_ww_ctx_fini(struct i915_gem_ww_ctx *ctx);
>  int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ctx);
>  void i915_gem_ww_unlock_single(struct drm_i915_gem_object *obj);
> +
> +/* Internal functions used by the inlines! Don't use. */
> +static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
> +{
> +	ww->loop = 0;
> +	if (err == -EDEADLK) {
> +		err = i915_gem_ww_ctx_backoff(ww);
> +		if (!err)
> +			ww->loop = 1;
> +	}
> +
> +	if (!ww->loop)
> +		i915_gem_ww_ctx_fini(ww);
> +
> +	return err;
> +}
> +
> +static inline void
> +__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
> +{
> +	i915_gem_ww_ctx_init(ww, intr);
> +	ww->loop = 1;
> +}
> +
> +#define for_i915_gem_ww(_ww, _err, _intr)			\
> +	for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop;	\
> +	     _err = __i915_gem_ww_fini(_ww, _err))
> +
>  #endif

With some more macro abuse, we should be able to kill off ww->loop,

for (err = ({i915_gem_ww_ctx_init(ww, intr), -EDEADLK}); err == -EDEADLK; err = (err == -EDEADLK && !(err = i915_gem_ww_ctx_backoff(ww))) ? -EDEADLK : err)

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