From: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
To: Jakob Koschel <jakobkoschel@gmail.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Felipe Balbi <balbi@kernel.org>, Joel Stanley <joel@jms.id.au>,
Andrew Jeffery <andrew@aj.id.au>,
Nicolas Ferre <nicolas.ferre@microchip.com>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Claudiu Beznea <claudiu.beznea@microchip.com>,
Cristian Birsan <cristian.birsan@microchip.com>,
Al Cooper <alcooperx@gmail.com>, Li Yang <leoyang.li@nxp.com>,
Vladimir Zapolskiy <vz@mleia.com>,
Daniel Mack <daniel@zonque.org>,
Haojian Zhuang <haojian.zhuang@gmail.com>,
Robert Jarzmik <robert.jarzmik@free.fr>,
Alim Akhtar <alim.akhtar@samsung.com>,
Thierry Reding <thierry.reding@gmail.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Michal Simek <michal.simek@xilinx.com>,
"open list:USB GADGET/PERIPHERAL SUBSYSTEM"
<linux-usb@vger.kernel.org>, Mike Rapoport <rppt@kernel.org>,
Brian Johannesmeyer <bjohannesmeyer@gmail.com>,
Cristiano Giuffrida <c.giuffrida@vu.nl>,
"Bos, H.J." <h.j.bos@vu.nl>
Subject: Re: [PATCH v2 14/26] usb: gadget: s3c-hsudc: remove usage of list iterator past the loop body
Date: Wed, 9 Mar 2022 18:56:31 +0100 [thread overview]
Message-ID: <6867439a-b995-86e7-6136-bcb8709eeb90@canonical.com> (raw)
In-Reply-To: <B269AAED-135D-4EAB-AA7C-26219581FB40@gmail.com>
On 09/03/2022 18:36, Jakob Koschel wrote:
>
>> On 9. Mar 2022, at 18:25, Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> wrote:
>>
>> On 08/03/2022 18:18, Jakob Koschel wrote:
>>> If the list representing the request queue does not contain the expected
>>> request, the value of the list_for_each_entry() iterator will not point
>>> to a valid structure. To avoid type confusion in such case, the list
>>> iterator scope will be limited to the list_for_each_entry() loop.
>>>
>>> In preparation to limiting scope of the list iterator to the list traversal
>>> loop, use a dedicated pointer to point to the found request object [1].
>>>
>>> Link: https://lore.kernel.org/all/YhdfEIwI4EdtHdym@kroah.com/
>>> Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
>>> ---
>>> drivers/usb/gadget/udc/s3c-hsudc.c | 12 +++++++-----
>>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/usb/gadget/udc/s3c-hsudc.c b/drivers/usb/gadget/udc/s3c-hsudc.c
>>> index 89f1f8c9f02e..bf803e013458 100644
>>> --- a/drivers/usb/gadget/udc/s3c-hsudc.c
>>> +++ b/drivers/usb/gadget/udc/s3c-hsudc.c
>>> @@ -877,7 +877,7 @@ static int s3c_hsudc_dequeue(struct usb_ep *_ep, struct usb_request *_req)
>>> {
>>> struct s3c_hsudc_ep *hsep = our_ep(_ep);
>>> struct s3c_hsudc *hsudc = hsep->dev;
>>> - struct s3c_hsudc_req *hsreq;
>>> + struct s3c_hsudc_req *hsreq = NULL, *iter;
>>> unsigned long flags;
>>>
>>> hsep = our_ep(_ep);
>>> @@ -886,11 +886,13 @@ static int s3c_hsudc_dequeue(struct usb_ep *_ep, struct usb_request *_req)
>>>
>>> spin_lock_irqsave(&hsudc->lock, flags);
>>>
>>> - list_for_each_entry(hsreq, &hsep->queue, queue) {
>>> - if (&hsreq->req == _req)
>>> - break;
>>> + list_for_each_entry(iter, &hsep->queue, queue) {
>>> + if (&iter->req != _req)
>>> + continue;
>>> + hsreq = iter;
>>> + break;
>>
>> You have in the loop both continue and break, looks a bit complicated.
>> Why not simpler:
>>
>> if (&iter->req == _req) {
>> hsreq = iter;
>> break;
>> }
>
> Ultimately I changed this based on the feedback from Linus
> (Link: https://lore.kernel.org/linux-kernel/CAHk-=wheru6rEfzC2wuO9k03PRF6s3nhxryCAnwR5bzKwPV2ww@mail.gmail.com/).
Not cleaner to me at all, but it's all personal opinion. :)
>>
>> ?
>> Less code, typical (expected) code flow when looking for something in
>> the list. Is your approach related to some speculative execution?
>
> no relation to speculative execution.
>
> I have no preference for one over the other, so I'll just change it to
> however it is desired.
>
> It would just be great to have a (somewhat) consistent way so I can prepare
> the rest of the patch sets accordingly.
>
Yeah, I understand. The code itself looks good, so:
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Best regards,
Krzysztof
next prev parent reply other threads:[~2022-03-09 17:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-08 17:17 [PATCH v2 00/26] usb: gadget: remove usage of list iterator past the loop Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 01/26] usb: gadget: fsl: remove usage of list iterator past the loop body Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 02/26] usb: gadget: bdc: " Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 03/26] usb: gadget: udc: atmel: " Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 04/26] usb: gadget: udc: pxa25x: " Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 05/26] usb: gadget: udc: at91: " Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 06/26] usb: gadget: goku_udc: " Jakob Koschel
2022-03-08 17:17 ` [PATCH v2 07/26] usb: gadget: udc: gr_udc: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 08/26] usb: gadget: lpc32xx_udc: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 09/26] usb: gadget: mv_u3d: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 10/26] usb: gadget: udc: mv_udc_core: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 11/26] usb: gadget: net2272: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 12/26] usb: gadget: udc: net2280: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 13/26] usb: gadget: omap_udc: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 14/26] usb: gadget: s3c-hsudc: " Jakob Koschel
2022-03-09 17:25 ` Krzysztof Kozlowski
2022-03-09 17:36 ` Jakob Koschel
2022-03-09 17:56 ` Krzysztof Kozlowski [this message]
2022-03-08 17:18 ` [PATCH v2 15/26] usb: gadget: udc-xilinx: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 16/26] usb: gadget: aspeed: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 17/26] usb: gadget: configfs: remove using list iterator after loop body as a ptr Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 18/26] usb: gadget: legacy: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 19/26] usb: gadget: udc: max3420_udc: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 20/26] usb: gadget: tegra-xudc: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 21/26] usb: gadget: composite: remove check of list iterator against head past the loop body Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 22/26] usb: gadget: pxa27x_udc: replace usage of rc to check if a list element was found Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 23/26] usb: gadget: composite: remove usage of list iterator past the loop body Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 24/26] usb: gadget: udc: core: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 25/26] usb: gadget: dummy_hcd: " Jakob Koschel
2022-03-08 17:18 ` [PATCH v2 26/26] usb: gadget: udc: s3c2410: " Jakob Koschel
2022-03-09 17:20 ` Krzysztof Kozlowski
2022-03-08 21:17 ` [PATCH v2 00/26] usb: gadget: remove usage of list iterator past the loop Linus Torvalds
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