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

[Alex Deucher]

On Sun, Dec 11, 2016 at 12:12 PM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> On Tue, Nov 15, 2016 at 10:43:34PM +0100, Daniel Vetter wrote:
>> 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.
>
> Anyone want to second these ww_mutex wrappers for reservation objects?

Looks good to me.

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

>
>> > + * 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
>
> --
> Chris Wilson, Intel Open Source Technology Centre
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