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List: linaro-mm-sig
Subject: Re: [Linaro-mm-sig] [PATCH] dma-buf: make dma_fence structure a bit smaller v2
From: Daniel Vetter <daniel () ffwll ! ch>
Date: 2019-08-08 19:11:54
Message-ID: 20190808191154.GP7444 () phenom ! ffwll ! local
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On Thu, Aug 08, 2019 at 04:41:39PM +0200, Christian König wrote:
> Daniel any more comments on this one?
It's not kerneldoc, but then all the dma-* docs need some serious love
anyway, so all good with me.
-Daniel
>
> If not I'm going to push it.
>
> Christian.
>
> Am 08.08.19 um 15:22 schrieb Christian König:
> > We clear the callback list on kref_put so that by the time we
> > release the fence it is unused. No one should be adding to the cb_list
> > that they don't themselves hold a reference for.
> >
> > This small change is actually making the structure 16% smaller.
> >
> > v2: add the comment to the code as well.
> >
> > Signed-off-by: Christian König <christian.koenig@amd.com>
> > Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> > ---
> > include/linux/dma-fence.h | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> > index 05d29dbc7e62..bea1d05cf51e 100644
> > --- a/include/linux/dma-fence.h
> > +++ b/include/linux/dma-fence.h
> > @@ -65,8 +65,14 @@ struct dma_fence_cb;
> > struct dma_fence {
> > struct kref refcount;
> > const struct dma_fence_ops *ops;
> > - struct rcu_head rcu;
> > - struct list_head cb_list;
> > + /* We clear the callback list on kref_put so that by the time we
> > + * release the fence it is unused. No one should be adding to the cb_list
> > + * that they don't themselves hold a reference for.
> > + */
> > + union {
> > + struct rcu_head rcu;
> > + struct list_head cb_list;
> > + };
> > spinlock_t *lock;
> > u64 context;
> > u64 seqno;
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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