linux-kernel - Re: [RFC 1/5] dma-buf/fence: add .teardown() ops

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Message-ID: <20160623204814.GC1086@nuc-i3427.alporthouse.com>
Date:	Thu, 23 Jun 2016 21:48:14 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Gustavo Padovan <gustavo@...ovan.org>
Cc:	dri-devel@...ts.freedesktop.org, marcheu@...gle.com,
	Daniel Stone <daniels@...labora.com>, seanpaul@...gle.com,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-kernel@...r.kernel.org, laurent.pinchart@...asonboard.com,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
	John Harrison <John.C.Harrison@...el.com>, m.chehab@...sung.com
Subject: Re: [RFC 1/5] dma-buf/fence: add .teardown() ops

On Thu, Jun 23, 2016 at 12:29:46PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> 
> fence_array requires a function to clean up its state before we
> are able to call fence_put() and release it.

An explanation along the lines of:

As the array of fence callbacks held by an active struct fence_array
each has a reference to the struct fence_array, when the owner of the
fence_array is freed it must dispose of the callback references before
it can free the fence_array. This can not happen simply during
fence_release() because of the extra references and so we need a new
function to run before the final fence_put().

would help, it is not until you use it in 5/5 that it becomes apparent
why it is needed.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre