[Intel-gfx] [PATCH] dma-buf: Provide wrappers for reservation's lock

[Daniel Vetter]

On Tue, Nov 15, 2016 at 03:46:42PM +0000, Chris Wilson wrote:
> Joonas complained that writing ww_mutex_lock(&resv->lock, ctx) was too
> intrusive compared to reservation_object_lock(resv, ctx);
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Sumit Semwal <sumit.semwal at linaro.org>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  include/linux/reservation.h | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/include/linux/reservation.h b/include/linux/reservation.h
> index ed238961e1bf..9cfc0d857862 100644
> --- a/include/linux/reservation.h
> +++ b/include/linux/reservation.h
> @@ -129,6 +129,40 @@ reservation_object_fini(struct reservation_object *obj)
>  }
>  
>  /**
> + * reservation_object_lock - lock the reservation object
> + * @obj: the reservation object
> + * @ctx: the locking context
> + *
> + * Locks the reservation object for exclusive access and modification. Note,
> + * that the lock is only against other writers, readers will run concurrently
> + * with a writer under RCU. The seqlock is used to notify readers if they
> + * overlap with a writer.
> + *
> + * As the reservation object may be locked by multiple parties in an
> + * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle

s/#/&/ for struct references. Otherwise the magic hotlink won't appear
(once we get around to pulling all the core docs into the overall sphinx
build). I can fix this while applying if everyone else is ok with the
patch - imo it makes sense.
-Daniel

> + * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation
> + * object may be locked by itself by passing NULL as @ctx.
> + */
> +static inline int
> +reservation_object_lock(struct reservation_object *obj,
> +			struct ww_acquire_ctx *ctx)
> +{
> +	return ww_mutex_lock(&obj->lock, ctx);
> +}
> +
> +/**
> + * reservation_object_unlock - unlock the reservation object
> + * @obj: the reservation object
> + *
> + * Unlocks the reservation object following exclusive access.
> + */
> +static inline void
> +reservation_object_unlock(struct reservation_object *obj)
> +{
> +	ww_mutex_unlock(&obj->lock);
> +}
> +
> +/**
>   * reservation_object_get_excl - get the reservation object's
>   * exclusive fence, with update-side lock held
>   * @obj: the reservation object
> -- 
> 2.10.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch