linux-kernel - Re: [PATCH 3/3] DMA: PL330: Balance module remove function with probe

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Message-ID: <CABb+yY3iw5dWyKsdcOawMad+7L7HkyEZaHnvwQ4VUQ5Br4BoBw@mail.gmail.com>
Date:	Thu, 27 Sep 2012 11:33:10 +0530
From:	Jassi Brar <jassisinghbrar@...il.com>
To:	Inderpal Singh <inderpal.singh@...aro.org>
Cc:	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	boojin.kim@...sung.com, vinod.koul@...el.com, patches@...aro.org,
	kgene.kim@...sung.com
Subject: Re: [PATCH 3/3] DMA: PL330: Balance module remove function with probe

On Thu, Sep 27, 2012 at 11:00 AM, Inderpal Singh
<inderpal.singh@...aro.org> wrote:
> On 27 September 2012 10:35, Jassi Brar <jassisinghbrar@...il.com> wrote:
>> On Thu, Sep 27, 2012 at 9:43 AM, Inderpal Singh
>> <inderpal.singh@...aro.org> wrote:
>>>
>>> Don't you think free_chan_resource should be done __only if__
>>> alloc_chan_resource was successful ?
>>>
>> No, I don't think so. Thanks.
>
> Thanks for quick response.
> Please elaborate more on this as I find it against the general rule
> and against the dmaengine implementation which checks on the same
> condition before proceeding for free_chan_resouces in dma_chan_put
> function.
>
I thought I already explained it, but here is the summary.
Calling pl330_free_chan_resources() for channels that have zero client
is already safe. Preventing the call by checking !client_count only
increases LOC making it uglier.

** If the new check provides any more security, please let me know. **

Food for thought : we never check for NULL before passing a pointer to
kfree(). Why ?
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