From: Jonathan Cameron <jic23@kernel.org>
To: "Nuno Sá" <noname.nuno@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
"Sa, Nuno" <Nuno.Sa@analog.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-rockchip@lists.infradead.org"
<linux-rockchip@lists.infradead.org>,
"linux-amlogic@lists.infradead.org"
<linux-amlogic@lists.infradead.org>,
"linux-imx@nxp.com" <linux-imx@nxp.com>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
Chunyan Zhang <zhang.lyra@gmail.com>,
"Hennerich, Michael" <Michael.Hennerich@analog.com>,
Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
Sascha Hauer <s.hauer@pengutronix.de>,
Cixi Geng <cixi.geng1@unisoc.com>,
Kevin Hilman <khilman@baylibre.com>,
Vladimir Zapolskiy <vz@mleia.com>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Alexandru Ardelean <aardelean@deviqon.com>,
Fabio Estevam <festevam@gmail.com>,
Andriy Tryshnivskyy <andriy.tryshnivskyy@opensynergy.com>,
Haibo Chen <haibo.chen@nxp.com>, Shawn Guo <shawnguo@kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
Miquel Raynal <miquel.raynal@bootlin.com>,
Jerome Brunet <jbrunet@baylibre.com>,
Heiko Stuebner <heiko@sntech.de>,
Florian Boor <florian.boor@kernelconcepts.de>,
"Regus, Ciprian" <Ciprian.Regus@analog.com>,
Lars-Peter Clausen <lars@metafoo.de>,
Neil Armstrong <narmstrong@baylibre.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Jyoti Bhayana <jbhayana@google.com>, Chen-Yu Tsai <wens@csie.org>,
Orson Zhai <orsonzhai@gmail.com>
Subject: Re: [PATCH 03/15] iio: adc: axp288_adc: do not use internal iio_dev lock
Date: Sat, 24 Sep 2022 16:23:29 +0100 [thread overview]
Message-ID: <20220924162329.5f0dd680@jic23-huawei> (raw)
In-Reply-To: <c487df06699aa53292909ff6be2b07de324793f4.camel@gmail.com>
On Wed, 21 Sep 2022 11:07:50 +0200
Nuno Sá <noname.nuno@gmail.com> wrote:
> On Tue, 2022-09-20 at 18:12 +0300, Andy Shevchenko wrote:
> > On Tue, Sep 20, 2022 at 4:46 PM Sa, Nuno <Nuno.Sa@analog.com> wrote:
> > > > -----Original Message-----
> > > > From: Andy Shevchenko <andy.shevchenko@gmail.com>
> > > > Sent: Tuesday, September 20, 2022 3:39 PM
> > > > On Tue, Sep 20, 2022 at 4:37 PM Andy Shevchenko
> > > > <andy.shevchenko@gmail.com> wrote:
> > > > > On Tue, Sep 20, 2022 at 4:18 PM Sa, Nuno <Nuno.Sa@analog.com>
> > > > > wrote:
> > > > > > > On Tue, Sep 20, 2022 at 2:28 PM Nuno Sá
> > > > > > > <nuno.sa@analog.com>
> > > > wrote:
> > > >
> > > > ...
> > > >
> > > > > > > > info = iio_priv(indio_dev);
> > > > > > > > + mutex_init(&info->lock);
> > > > > > > > info->irq = platform_get_irq(pdev, 0);
> > > > > > > > if (info->irq < 0)
> > > > > > > > return info->irq;
> > > > > > >
> > > > > > > Consider initializing it as late as possible, like after
> > > > > > > IRQ retrieval
> > > > > > > in this context (maybe even deeper, but no context
> > > > > > > available). Ditto
> > > > > > > for the rest of the series.
> > > > > >
> > > > > > Any special reason for it (maybe related to lockdep
> > > > > > :wondering: ) ? Just
> > > > > > curious as I never noticed such a pattern when initializing
> > > > > > mutexes.
> > > > >
> > > > > Yes. Micro-optimization based on the rule "don't create a
> > > > > resource in
> > > > > case of known error".
> > > > >
> > > > > OTOH, you have to be sure that the mutex (and generally
> > > > > speaking a
> > > > > locking) should be initialized early enough.
> > >
> > > Typically not really needed during probe...
> >
> > Actually as long as you expose the ABI to the user anything can
> > happen, means that your code should be ready to receive the requests
> > in any possible callbacks / file ops. Same applies to the IRQ
> > handler.
> > So it's very important to initialize locking just in time. Hence I
> > can
> > say that "typically it needs to be carefully placed".
> >
>
> Yes, I'm aware of that... For some reason I just thought about code
> paths directly on probe. Anyways, hopefully these drivers mostly do the
> right thing and register the IIO device as late as possible (ideally
> the last thing to be done). The same goes for IRQs and for IIO, when
> used as part of triggered buffering, the lock is often only used in the
> trigger handler which means it's only reachable after the ABI is
> exposed...
Can't say I feel that strongly about a mutex_init() placement, but
no harm in moving them later - indeed before the iio_device_register()
should be correct - though care needed as might be some unnecessary locks
taken in probe because of code sharing (and them previously being harmless)
Jonathan
>
> - Nuno Sá
> > >
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next prev parent reply other threads:[~2022-09-24 15:23 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-20 11:28 [PATCH 00/15] Make 'mlock' really private Nuno Sá
2022-09-20 11:28 ` [PATCH 01/15] iio: adc: ad_sigma_delta: do not use internal iio_dev lock Nuno Sá
2022-09-20 11:54 ` Miquel Raynal
2022-09-24 14:22 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 02/15] iio: adc: ad799x: " Nuno Sá
2022-09-24 14:45 ` Jonathan Cameron
2022-09-26 11:22 ` Nuno Sá
2022-09-20 11:28 ` [PATCH 03/15] iio: adc: axp288_adc: " Nuno Sá
2022-09-20 13:13 ` Andy Shevchenko
2022-09-20 13:18 ` Sa, Nuno
2022-09-20 13:37 ` Andy Shevchenko
2022-09-20 13:39 ` Andy Shevchenko
2022-09-20 13:46 ` Sa, Nuno
2022-09-20 15:12 ` Andy Shevchenko
2022-09-21 9:07 ` Nuno Sá
2022-09-24 15:23 ` Jonathan Cameron [this message]
2022-09-24 15:24 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 04/15] iio: adc: imx7d_adc: " Nuno Sá
2022-09-24 15:26 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 05/15] iio: adc: lpc32xx_adc: " Nuno Sá
2022-09-24 15:27 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 06/15] iio: adc: ltc2947-core: " Nuno Sá
2022-09-20 11:28 ` [PATCH 07/15] iio: adc: meson_saradc: " Nuno Sá
2022-09-25 20:38 ` Martin Blumenstingl
2022-09-20 11:28 ` [PATCH 08/15] iio: adc: rockchip_saradc: " Nuno Sá
2022-09-20 11:28 ` [PATCH 09/15] iio: adc: sc27xx_adc: " Nuno Sá
2022-09-20 11:28 ` [PATCH 10/15] iio: adc: vf610_adc: " Nuno Sá
2022-09-24 15:37 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 11/15] iio: common: scmi_iio: " Nuno Sá
2022-09-24 15:42 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 12/15] iio: fyro: itg3200_core: " Nuno Sá
2022-09-24 15:43 ` Jonathan Cameron
2022-09-24 15:46 ` Jonathan Cameron
2022-09-20 11:28 ` [PATCH 13/15] iio: health: max30100: " Nuno Sá
2022-09-20 12:23 ` Miquel Raynal
2022-09-20 12:44 ` Sa, Nuno
2022-09-20 12:55 ` Miquel Raynal
2022-09-20 13:15 ` Sa, Nuno
2022-09-20 13:53 ` Miquel Raynal
2022-09-20 14:56 ` Nuno Sá
2022-09-20 15:10 ` Miquel Raynal
2022-09-24 15:53 ` Jonathan Cameron
2022-09-26 10:06 ` Nuno Sá
2022-10-02 11:03 ` Jonathan Cameron
2022-10-04 7:57 ` Nuno Sá
2022-09-20 11:28 ` [PATCH 14/15] iio: health: max30102: " Nuno Sá
2022-09-24 15:54 ` Jonathan Cameron
2022-09-30 10:04 ` Nuno Sá
2022-10-02 11:08 ` Jonathan Cameron
2022-10-04 7:53 ` Nuno Sá
2022-09-20 11:28 ` [PATCH 15/15] iio: core: move 'mlock' to 'struct iio_dev_opaque' Nuno Sá
2022-09-24 15:56 ` Jonathan Cameron
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