linux-kernel - Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the callback

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Date:   Fri, 19 Aug 2016 08:18:53 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        linux-arm-msm@...r.kernel.org, timur@...eaurora.org,
        linux-kernel@...r.kernel.org,
        Christopher Covington <cov@...eaurora.org>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the
 callback

<sorry for delay, i was out>

On Wed, Aug 10, 2016 at 01:31:21PM -0400, Sinan Kaya wrote:
> On 8/10/2016 1:28 PM, Vinod Koul wrote:
> >> That's why, I preferred not to call the callback when I observe an error which I
> >> > think it makes more sense. 
> > That doesnt make sense. A client set a callback, it expect you to call one.
> > The result quried maybe txn completed or error. Since you have means, please
> > report..
> > 
> 
> If there is a good way to fix tx_status, I can certainly do so. I just need to make
> sure my implementation is robust and reliable.
> 
> I saw your reply that we need to keep this information around until terminate_all is
> called. 
> 
> What is a good implementation strategy?
> 
> Keep a size limited list with error cookies and flush them in terminate all?

I think so, terminate_all anyway cleans up the channel. Btw what is the
behaviour on error? Do you terminate or somthing else?

> What should I do if code reaches to the size limit?
> 
> Size the error cookie list double the size of available descriptors?

That won't help as you would have two values per cookie and we dont want
that :)

> >> Again, it will be a different patch than this one. I think v2 of this patch
> >> > needs to go in as it is.
> >> > 
> >> > https://lkml.org/lkml/2016/7/31/64
> > I havent looked at the patch. If it is not invoking callback set by user,
> > then I am not taking it. Sorry, we dont choose over client's wish.
> 
> Ok. The problem you are referring to is something else and needs to be addressed
> separately. I can create a series with first implement a reliable tx_status based
> on your recommendation above.
> 
> Then, change the current behavior so that client callback is always executed as you
> requested.
> 
> After that this patch to fix the free order.

-- 
~Vinod