From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: Marcus Folkesson <marcus.folkesson@gmail.com>,
Kent Gustavsson <kent@minoris.se>,
Lars-Peter Clausen <lars@metafoo.de>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
linux-iio <linux-iio@vger.kernel.org>,
devicetree <devicetree@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 02/10] iio: adc: mcp3911: use resource-managed version of iio_device_register
Date: Tue, 28 Jun 2022 14:01:08 +0200 [thread overview]
Message-ID: <CAHp75Vdr87rXRAKHtxftkPEbS+2yAp8a+Cp1Jx0XnozL+WCKVw@mail.gmail.com> (raw)
In-Reply-To: <20220625122429.14e98106@jic23-huawei>
On Sat, Jun 25, 2022 at 1:15 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Fri, 24 Jun 2022 08:29:20 +0200
> Marcus Folkesson <marcus.folkesson@gmail.com> wrote:
>
> > Thank you for your comments (all of them) Andy!
> >
> > On Thu, Jun 23, 2022 at 09:01:59PM +0200, Andy Shevchenko wrote:
> > > On Thu, Jun 23, 2022 at 7:40 PM Marcus Folkesson
> > > <marcus.folkesson@gmail.com> wrote:
> > > >
> > > > Keep using managed resources as much as possible.
> > >
> > > You may not mix devm_ and non-devm_ API calls like this.
> > > So, you rule of thumb that goto is most of the time wrong after devm_ call.
> >
> > Can you please confirm that clocks and regulators are disabled when the
> > resources are handed back?
> > I cannot see where when I'm trying to follow the code.
> Andy isn't arguing that the goto is wrong but rather that you cannot
> in general safely use devm_* calls if their failure leads to having to
> do any cleanup. The reason is the ordering is hard to reason about. Sometimes
> it's safe, but often enough causes problems that we basically refuse to think
> hard enough to figure out if it is. Hence basic rule is don't do it.
>
> The issue is this.
> probe() {
>
> non_devm_call_1();
> ret = devm_call_2()
> if (ret)
> goto err;
>
> return 0;
> err:
> unwind_non_devm_call_1()
> }
>
> remove() {
> unwind_non_devm_call_1()
> }
>
> remove or error path should unwind in opposite order of what happens in probe.
> On the rare occasion where that isn't the right choice, there should be very
> clear comments to say why.
>
> Order is
>
> remove() -> unwind_non_devm_call_1()
> devm_managed_cleanup() -> unwind_devm_call_2()
>
> Whereas should be
>
> remove()-> unwind_call_2() then unwind_call_1()
>
>
> There are two ways to solve this. Either only use devm for those
> elements in probe() that happen before the first thing you need to
> unwind manually or make everything devm managed (it unwinds in reverse
> order of setup) devm_add_action_or_reset() allows you to use your
> own devm_ managed callbacks if there isn't a standard one available.
Thanks, Jonathan, that's exactly what I meant!
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-06-28 12:01 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-23 17:08 [PATCH 01/10] iio: adc: mcp3911: correct "microchip,device-addr" property Marcus Folkesson
2022-06-23 17:08 ` [PATCH 02/10] iio: adc: mcp3911: use resource-managed version of iio_device_register Marcus Folkesson
2022-06-23 19:01 ` Andy Shevchenko
2022-06-24 6:29 ` Marcus Folkesson
2022-06-25 11:24 ` Jonathan Cameron
2022-06-28 12:01 ` Andy Shevchenko [this message]
2022-06-23 17:08 ` [PATCH 03/10] iio: adc: mcp3911: add support for buffers Marcus Folkesson
2022-06-23 17:08 ` [PATCH 04/10] iio: adc: mcp3911: add support for interrupts Marcus Folkesson
2022-06-23 19:04 ` Andy Shevchenko
2022-06-24 12:01 ` Marcus Folkesson
2022-06-23 17:08 ` [PATCH 05/10] dt-bindings: iio: adc: mcp3911: add microchip,data-ready-hiz entry Marcus Folkesson
2022-06-24 9:54 ` Krzysztof Kozlowski
2022-06-24 12:10 ` Marcus Folkesson
2022-06-24 17:26 ` Rob Herring
2022-06-23 17:08 ` [PATCH 06/10] iio: adc: mcp3911: add support for oversampling ratio Marcus Folkesson
2022-06-23 19:20 ` Andy Shevchenko
2022-06-24 12:09 ` Marcus Folkesson
2022-06-28 11:56 ` Andy Shevchenko
2022-06-23 17:08 ` [PATCH 07/10] iio: adc: mcp3911: use correct formula for AD conversion Marcus Folkesson
2022-06-23 17:08 ` [PATCH 08/10] iio: adc: mcp3911: add support for phase Marcus Folkesson
2022-06-23 19:07 ` Andy Shevchenko
2022-06-24 12:02 ` Marcus Folkesson
2022-06-25 11:33 ` Jonathan Cameron
2022-06-23 17:08 ` [PATCH 09/10] iio: adc: mcp3911: make use of the sign bit Marcus Folkesson
2022-06-23 17:08 ` [PATCH 10/10] iio: adc: mcp3911: add support to set PGA Marcus Folkesson
2022-06-23 17:26 ` Marcus Folkesson
2022-06-23 19:15 ` Andy Shevchenko
2022-06-24 12:05 ` Marcus Folkesson
2022-06-23 18:59 ` [PATCH 01/10] iio: adc: mcp3911: correct "microchip,device-addr" property Andy Shevchenko
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=CAHp75Vdr87rXRAKHtxftkPEbS+2yAp8a+Cp1Jx0XnozL+WCKVw@mail.gmail.com \
--to=andy.shevchenko@gmail.com \
--cc=devicetree@vger.kernel.org \
--cc=jic23@kernel.org \
--cc=kent@minoris.se \
--cc=krzysztof.kozlowski+dt@linaro.org \
--cc=lars@metafoo.de \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=marcus.folkesson@gmail.com \
--cc=robh+dt@kernel.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 NNTP newsgroup(s).