From: Dan Carpenter <dan.carpenter@linaro.org>
To: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: "Ricardo Ribalda" <ribalda@chromium.org>,
"Martin Tuma" <martin.tuma@digiteqautomotive.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
"Hans Verkuil" <hverkuil-cisco@xs4all.nl>,
"Hugues Fruchet" <hugues.fruchet@foss.st.com>,
"Alain Volmat" <alain.volmat@foss.st.com>,
"Maxime Coquelin" <mcoquelin.stm32@gmail.com>,
"Alexandre Torgue" <alexandre.torgue@foss.st.com>,
"Paul Kocialkowski" <paul.kocialkowski@bootlin.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Chen-Yu Tsai" <wens@csie.org>,
"Jernej Skrabec" <jernej.skrabec@gmail.com>,
"Samuel Holland" <samuel@sholland.org>,
"Sakari Ailus" <sakari.ailus@linux.intel.com>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Jonathan Hunter" <jonathanh@nvidia.com>,
"Sowjanya Komatineni" <skomatineni@nvidia.com>,
"Luca Ceresoli" <luca.ceresoli@bootlin.com>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"AngeloGioacchino Del Regno"
<angelogioacchino.delregno@collabora.com>,
"Hans Verkuil" <hverkuil@xs4all.nl>,
"Sergey Kozlov" <serjk@netup.ru>,
"Abylay Ospan" <aospan@netup.ru>,
"Ezequiel Garcia" <ezequiel@vanguardiasur.com.ar>,
"Dmitry Osipenko" <digetx@gmail.com>,
"Stanimir Varbanov" <stanimir.k.varbanov@gmail.com>,
"Vikash Garodia" <quic_vgarodia@quicinc.com>,
"Bjorn Andersson" <andersson@kernel.org>,
"Konrad Dybcio" <konrad.dybcio@linaro.org>,
"Benjamin Mugnier" <benjamin.mugnier@foss.st.com>,
"Sylvain Petinot" <sylvain.petinot@foss.st.com>,
"Jacopo Mondi" <jacopo+renesas@jmondi.org>,
"Kieran Bingham" <kieran.bingham+renesas@ideasonboard.com>,
"Laurent Pinchart" <laurent.pinchart+renesas@ideasonboard.com>,
"Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
"Pavel Machek" <pavel@ucw.cz>,
linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-stm32@st-md-mailman.stormreply.com,
linux-arm-kernel@lists.infradead.org,
linux-staging@lists.linux.dev, linux-sunxi@lists.linux.dev,
linux-tegra@vger.kernel.org, linux-mediatek@lists.infradead.org,
linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH 11/35] media: s2255: Use refcount_t instead of atomic_t for num_channels
Date: Tue, 23 Apr 2024 16:22:12 +0300 [thread overview]
Message-ID: <cf050593-44c2-4b4b-8198-215455c630f9@moroto.mountain> (raw)
In-Reply-To: <d13fd47e-1ecd-4aa8-844b-cd260e9fa437@linaro.org>
On Tue, Apr 23, 2024 at 01:43:49PM +0100, Bryan O'Donoghue wrote:
> On 15/04/2024 20:34, Ricardo Ribalda wrote:
> > Use an API that resembles more the actual use of num_channels.
> >
> > Found by cocci:
> > drivers/media/usb/s2255/s2255drv.c:2362:5-24: WARNING: atomic_dec_and_test variation before object free at line 2363.
> > drivers/media/usb/s2255/s2255drv.c:1557:5-24: WARNING: atomic_dec_and_test variation before object free at line 1558.
>
> Hmm, that commit log needs more detail.
>
> "Convert from atomic_t to refcount_t because refcount_t has memory ordering
> guarantees which atomic does not, hence the WARNING for the free after the
> atomic dec."
>
The memory ordering rules are the same. They're basically identical.
The difference is that if you decrement a refcount_t past zero it will
trigger an error and refuse but atomic_t will merrily keep decrementing
forever. With refcount_t you can still have a use after free bug but
afterward the double free will trigger a warning.
There are time where people use atomic_t to get unique number and don't
care about wrapping so that's fine. But if it's reference counting then
use refcount_t.
There wouldn't be a Fixes tag in this case, because hopefully it's just
hardenning and not a bugfix.
regards,
dan carpenter
next prev parent reply other threads:[~2024-04-23 13:22 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-15 19:34 [PATCH 00/35] media: Fix coccinelle warning/errors Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 01/35] media: pci: mgb4: Refactor struct resources Ricardo Ribalda
2024-04-16 11:30 ` Martin Tůma
2024-04-15 19:34 ` [PATCH 02/35] media: stb0899: Remove unreacheable code Ricardo Ribalda
2024-04-16 7:32 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 03/35] media: uvcvideo: Refactor iterators Ricardo Ribalda
2024-04-16 4:39 ` Sergey Senozhatsky
2024-04-16 5:08 ` Sergey Senozhatsky
2024-04-16 7:03 ` Markus Elfring
2024-04-16 7:15 ` Greg Kroah-Hartman
2024-04-18 11:04 ` Laurent Pinchart
2024-04-15 19:34 ` [PATCH 04/35] media: uvcvideo: Use max() macro Ricardo Ribalda
2024-04-15 21:06 ` Kieran Bingham
2024-04-16 4:41 ` Sergey Senozhatsky
2024-04-18 10:54 ` Laurent Pinchart
2024-04-15 19:34 ` [PATCH 05/35] media: go7007: Use min and max macros Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 06/35] media: stm32-dcmipp: Remove redundant printk Ricardo Ribalda
2024-04-16 7:30 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 07/35] media: staging: sun6i-isp: " Ricardo Ribalda
2024-04-15 20:43 ` Jernej Škrabec
2024-04-16 7:37 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 08/35] media: dvb-frontends: tda18271c2dd: Remove casting during div Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 09/35] media: v4l: async: refactor v4l2_async_create_ancillary_links Ricardo Ribalda
2024-04-16 7:44 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 10/35] staging: media: tegra-video: Use swap macro Ricardo Ribalda
2024-04-16 2:03 ` Luca Ceresoli
2024-04-15 19:34 ` [PATCH 11/35] media: s2255: Use refcount_t instead of atomic_t for num_channels Ricardo Ribalda
2024-04-23 12:43 ` Bryan O'Donoghue
2024-04-23 13:22 ` Dan Carpenter [this message]
2024-04-15 19:34 ` [PATCH 12/35] media: platform: mtk-mdp3: Use refcount_t for job_count Ricardo Ribalda
2024-04-23 12:46 ` Bryan O'Donoghue
2024-04-15 19:34 ` [PATCH 13/35] media: common: saa7146: Use min macro Ricardo Ribalda
2024-04-23 12:49 ` Bryan O'Donoghue
2024-04-15 19:34 ` [PATCH 14/35] media: dvb-frontends: drx39xyj: " Ricardo Ribalda
2024-04-23 16:40 ` Bryan O'Donoghue
2024-04-15 19:34 ` [PATCH 15/35] media: netup_unidvb: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 16/35] media: au0828: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 17/35] media: flexcop-usb: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 18/35] media: gspca: cpia1: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 19/35] media: stk1160: " Ricardo Ribalda
2024-04-23 16:42 ` Bryan O'Donoghue
2024-04-15 19:34 ` [PATCH 20/35] media: tegra-vde: Refactor timeout handling Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 21/35] media: venus: Use div64_u64 Ricardo Ribalda
2024-04-16 7:57 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 22/35] media: i2c: st-mipid02: Use the correct div function Ricardo Ribalda
2024-04-17 12:55 ` Benjamin Mugnier
2024-04-15 19:34 ` [PATCH 23/35] media: dvb-frontends: tda10048: Use the right div Ricardo Ribalda
2024-04-16 10:10 ` Dan Carpenter
2024-04-16 10:27 ` Dan Carpenter
2024-04-23 9:55 ` Dan Carpenter
2024-04-29 11:39 ` Ricardo Ribalda
2024-04-16 10:39 ` Ricardo Ribalda
2024-04-16 10:56 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 24/35] media: tc358746: Use the correct div_ function Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 25/35] media: venus: " Ricardo Ribalda
2024-04-17 8:36 ` Dan Carpenter
2024-04-15 19:34 ` [PATCH 26/35] media: venus: Refator return path Ricardo Ribalda
2024-04-23 16:49 ` Bryan O'Donoghue
2024-04-15 19:34 ` [PATCH 27/35] media: dib0700: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 28/35] media: usb: cx231xx: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 29/35] media: i2c: rdacm20: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 30/35] media: i2c: et8ek8: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 31/35] media: cx231xx: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 32/35] media: si4713: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 33/35] media: ttpci: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 34/35] media: hdpvr: " Ricardo Ribalda
2024-04-15 19:34 ` [PATCH 35/35] media: venus: " Ricardo Ribalda
2024-04-15 19:53 ` [PATCH 00/35] media: Fix coccinelle warning/errors Laurent Pinchart
2024-04-15 19:58 ` Ricardo Ribalda
2024-04-15 20:33 ` Niklas Söderlund
2024-04-15 21:16 ` Ricardo Ribalda
2024-04-15 21:38 ` Niklas Söderlund
2024-04-16 7:08 ` Laurent Pinchart
2024-04-16 7:59 ` Julia Lawall
2024-04-16 8:47 ` Dan Carpenter
2024-04-17 15:51 ` Laurent Pinchart
2024-04-17 16:19 ` Ricardo Ribalda
2024-04-18 10:53 ` Laurent Pinchart
2024-04-18 14:51 ` Ricardo Ribalda
2024-04-18 15:46 ` Laurent Pinchart
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cf050593-44c2-4b4b-8198-215455c630f9@moroto.mountain \
--to=dan.carpenter@linaro.org \
--cc=alain.volmat@foss.st.com \
--cc=alexandre.torgue@foss.st.com \
--cc=andersson@kernel.org \
--cc=angelogioacchino.delregno@collabora.com \
--cc=aospan@netup.ru \
--cc=benjamin.mugnier@foss.st.com \
--cc=bryan.odonoghue@linaro.org \
--cc=digetx@gmail.com \
--cc=ezequiel@vanguardiasur.com.ar \
--cc=gregkh@linuxfoundation.org \
--cc=hugues.fruchet@foss.st.com \
--cc=hverkuil-cisco@xs4all.nl \
--cc=hverkuil@xs4all.nl \
--cc=jacopo+renesas@jmondi.org \
--cc=jernej.skrabec@gmail.com \
--cc=jonathanh@nvidia.com \
--cc=kieran.bingham+renesas@ideasonboard.com \
--cc=konrad.dybcio@linaro.org \
--cc=laurent.pinchart+renesas@ideasonboard.com \
--cc=laurent.pinchart@ideasonboard.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=linux-staging@lists.linux.dev \
--cc=linux-stm32@st-md-mailman.stormreply.com \
--cc=linux-sunxi@lists.linux.dev \
--cc=linux-tegra@vger.kernel.org \
--cc=luca.ceresoli@bootlin.com \
--cc=martin.tuma@digiteqautomotive.com \
--cc=matthias.bgg@gmail.com \
--cc=mchehab@kernel.org \
--cc=mcoquelin.stm32@gmail.com \
--cc=niklas.soderlund+renesas@ragnatech.se \
--cc=paul.kocialkowski@bootlin.com \
--cc=pavel@ucw.cz \
--cc=quic_vgarodia@quicinc.com \
--cc=ribalda@chromium.org \
--cc=sakari.ailus@linux.intel.com \
--cc=samuel@sholland.org \
--cc=serjk@netup.ru \
--cc=skomatineni@nvidia.com \
--cc=stanimir.k.varbanov@gmail.com \
--cc=sylvain.petinot@foss.st.com \
--cc=thierry.reding@gmail.com \
--cc=wens@csie.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).