Date: Thu, 16 Jul 2015 08:45:09 +0000 (GMT)
From: Maninder Singh <maninder1.s@samsung.com>
Subject: Re: [RESEND PATCH 1/1] staging:vt6655: remove checks around
 dev_kfree_skb
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "forest@alittletooquiet.net" <forest@alittletooquiet.net>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
        "gclement@baobob.org" <gclement@baobob.org>,
        "tvboxspy@gmail.com" <tvboxspy@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "joe@perches.com" <joe@perches.com>,
        PANKAJ MISHRA <pankaj.m@samsung.com>
Reply-to: maninder1.s@samsung.com
MIME-version: 1.0
Msgkey: 20150716083444487@maninder1.s
Content-type: text/plain; charset=windows-1252
MIME-version: 1.0
Message-id: <686357594.854551437036306449.JavaMail.weblogic@ep2mlwas07d>
DLP-Filter: Pass
Sender: linux-kernel-owner@vger.kernel.org
Content-Transfer-Encoding: 8bit
Content-Length: 1594
Lines: 42

Hi Dan,

>I hate these patches.  I have told Markus to stop sending them but he
>has issues so now I only complain when they introduce a bug.  There was
>one bug I have missed because it was a benchmark regression and I knew
>it was theoretically possible but I didn't know the code well enough to
>say which were fast paths...

>My main objection is that relying on the sanity check inside the
>function call makes the code more subtle to understand.  We know we need
>a NULL check but it is hidden away in another file.  The motivation for
>this patch you are sending is "There is a sanity check in dev_kfree_skb()
>so let's do an insane thing and save some lines of code."

>For this particular patch we assume throughout the whole driver that
>"pTDInfo->skb" can be NULL so making it inconsistent in this one place
>is wrong

Agreed,
But these changes are suggested because:-

where we are checking for (pTDInfo->skb), we are using it  in above line.
and it does not look good, thats why we should remove thse checks and i have suggested
changes.

code snippet:-
-----------------------

if (pTDInfo->skb_dma && (pTDInfo->skb_dma != pTDInfo->buf_dma))
    dma_unmap_single(&pDevice->pcid->dev, pTDInfo->skb_dma,
             pTDInfo->skb->len, DMA_TO_DEVICE);

----> In this we did not check for pTDInfo->skb

if (pTDInfo->skb)
    dev_kfree_skb(pTDInfo->skb);

But if am wrong, sorry for the patch.

Thanks,
Maninder
............????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m????????????I?