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From: Stephen Boyd <swboyd@chromium.org>
To: Daniel Campello <campello@chromium.org>
Cc: LKML <devicetree@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Jonathan Cameron <jic23@kernel.org>,
	Douglas Anderson <dianders@chromium.org>,
	Enrico Granata <egranata@chromium.org>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	linux-iio <linux-iio@vger.kernel.org>
Subject: Re: [PATCH 10/15] iio: sx9310: Simplify error return handling
Date: Tue, 28 Jul 2020 14:32:28 -0700
Message-ID: <159597194837.1360974.9212489704079396891@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <CAHcu+VbYrbWStNNaidDygY=d4f6F5tXUxWtsuH0x3oVeELGWVA@mail.gmail.com>

Quoting Daniel Campello (2020-07-28 14:23:29)
> On Tue, Jul 28, 2020 at 1:40 PM Stephen Boyd <swboyd@chromium.org> wrote:
> >
> > Quoting Daniel Campello (2020-07-28 08:12:53)
> > > @@ -368,13 +368,13 @@ static int sx9310_wait_for_sample(struct sx9310_data *data)
> > >  static int sx9310_read_proximity(struct sx9310_data *data,
> > >                                  const struct iio_chan_spec *chan, int *val)
> > >  {
> > > -       int ret = 0;
> > > +       int ret;
> > >         __be16 rawval;
> > >
> > >         mutex_lock(&data->mutex);
> > >
> > >         ret = sx9310_get_read_channel(data, chan->channel);
> > > -       if (ret < 0)
> > > +       if (ret)
> > >                 goto out;
> > >
> > >         if (data->client->irq) {
> > > @@ -394,11 +394,11 @@ static int sx9310_read_proximity(struct sx9310_data *data,
> > >
> > >         mutex_lock(&data->mutex);
> > >
> > > -       if (ret < 0)
> > > +       if (ret)
> > >                 goto out_disable_irq;
> >
> > Why is this condition checked after grabbing the mutex? Shouldn't it be
> > checked before grabbing the mutex? Or is that supposed to be a
> > mutex_unlock()?
> We acquire the lock before jumping to out_disable_irq which is before
> a mutex_unlock()

Does this function need to hold the mutex lock around get/put_read_channel?
It drops the lock while waiting and then regrabs it which seems to
imply that another reader could come in and try to get the channel again
during the wait. So put another way, it may be simpler to shorten the
lock area and then bail out of this function to a place where the lock
isn't held already on the return path.

  reply index

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25  0:40 [PATCH] iio: sx9310: Fixes dropped on initial commit Daniel Campello
2020-07-26  8:10 ` Andy Shevchenko
2020-07-26 11:53 ` Jonathan Cameron
2020-07-28 15:12 ` [PATCH 00/15] sx9310 iio driver updates Daniel Campello
2020-07-28 15:12   ` [PATCH 01/15] dt-bindings: iio: Add bindings for sx9310 sensor Daniel Campello
2020-07-28 22:06     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 02/15] iio: sx9310: Update macros declarations Daniel Campello
2020-07-28 19:42     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 03/15] iio: sx9310: Fix irq handling Daniel Campello
2020-07-28 18:08     ` Andy Shevchenko
2020-07-28 20:07       ` Daniel Campello
2020-07-28 20:15         ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 04/15] iio: sx9310: Remove acpi and of table macros Daniel Campello
2020-07-28 18:09     ` Andy Shevchenko
2020-07-28 20:47       ` Daniel Campello
2020-07-28 21:28         ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 05/15] iio: sx9310: Change from .probe to .probe_new Daniel Campello
2020-07-28 18:10     ` Andy Shevchenko
2020-07-28 19:32     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 06/15] iio: sx9310: Align memory Daniel Campello
2020-07-28 18:11     ` Andy Shevchenko
2020-07-28 21:26       ` Daniel Campello
2020-07-29  6:52         ` Andy Shevchenko
2020-07-28 15:12   ` [PATCH 07/15] iio: sx9310: Use long instead of int for channel bitmaps Daniel Campello
2020-07-28 18:13     ` Andy Shevchenko
2020-07-28 19:37     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 08/15] iio: sx9310: Use regmap_read_poll_timeout() for compensation Daniel Campello
2020-07-28 18:14     ` Andy Shevchenko
2020-07-28 19:37     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 09/15] iio: sx9310: Update copyright Daniel Campello
2020-07-28 15:12   ` [PATCH 10/15] iio: sx9310: Simplify error return handling Daniel Campello
2020-07-28 18:15     ` Andy Shevchenko
2020-07-28 19:40     ` Stephen Boyd
2020-07-28 21:23       ` Daniel Campello
2020-07-28 21:32         ` Stephen Boyd [this message]
2020-07-28 22:06           ` Daniel Campello
2020-07-28 15:12   ` [PATCH 11/15] iio: sx9310: Use variable to hold &client->dev Daniel Campello
2020-07-28 18:16     ` Andy Shevchenko
2020-07-28 19:41     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 12/15] iio: sx9310: Miscellaneous format fixes Daniel Campello
2020-07-28 18:16     ` Andy Shevchenko
2020-07-28 19:41     ` Stephen Boyd
2020-07-28 15:12   ` [PATCH 13/15] iio: sx9310: Add newlines to printks Daniel Campello
2020-07-28 18:19     ` Andy Shevchenko
2020-07-28 18:24       ` Joe Perches
2020-07-28 18:32         ` Andy Shevchenko
2020-07-28 15:12   ` [PATCH 14/15] iio: sx9310: Drop channel_users[] Daniel Campello
2020-07-28 18:20     ` Andy Shevchenko
2020-07-28 15:12   ` [PATCH 15/15] iio: sx9310: Enable vdd and svdd regulators at probe Daniel Campello
2020-07-28 18:21     ` Andy Shevchenko
2020-07-28 23:05   ` [PATCH v2 00/14] sx9310 iio driver updates Daniel Campello
2020-07-28 23:05     ` [PATCH v2 01/14] dt-bindings: iio: Add bindings for sx9310 sensor Daniel Campello
2020-07-29  0:52       ` Stephen Boyd
2020-07-28 23:05     ` [PATCH v2 02/14] iio: sx9310: Update macros declarations Daniel Campello
2020-07-28 23:05     ` [PATCH v2 03/14] iio: sx9310: Fix irq handling Daniel Campello
2020-07-29  8:40       ` Stephen Boyd
2020-07-28 23:05     ` [PATCH v2 04/14] iio: sx9310: Remove acpi and of table macros Daniel Campello
2020-07-29  6:54       ` Andy Shevchenko
2020-07-29  8:38       ` Stephen Boyd
2020-07-28 23:05     ` [PATCH v2 05/14] iio: sx9310: Change from .probe to .probe_new Daniel Campello
2020-07-28 23:05     ` [PATCH v2 06/14] iio: sx9310: Fixes various memory handling Daniel Campello
2020-07-28 23:05     ` [PATCH v2 07/14] iio: sx9310: Use long instead of int for channel bitmaps Daniel Campello
2020-07-29  1:03       ` Stephen Boyd
2020-07-29  7:00         ` Andy Shevchenko
2020-07-31 15:44           ` Daniel Campello
2020-07-31 15:52             ` Andy Shevchenko
2020-07-28 23:05     ` [PATCH v2 08/14] iio: sx9310: Use regmap_read_poll_timeout() for compensation Daniel Campello
2020-07-28 23:05     ` [PATCH v2 09/14] iio: sx9310: Update copyright Daniel Campello
2020-07-28 23:05     ` [PATCH v2 10/14] iio: sx9310: Simplify error return handling Daniel Campello
2020-07-29  8:42       ` Stephen Boyd
2020-07-28 23:05     ` [PATCH v2 11/14] iio: sx9310: Use variable to hold &client->dev Daniel Campello
2020-07-28 23:05     ` [PATCH v2 12/14] iio: sx9310: Miscellaneous format fixes Daniel Campello
2020-07-28 23:05     ` [PATCH v2 13/14] iio: sx9310: Drop channel_users[] Daniel Campello
2020-07-28 23:05     ` [PATCH v2 14/14] iio: sx9310: Enable vdd and svdd regulators at probe Daniel Campello
2020-07-29  0:50     ` [PATCH v2 00/14] sx9310 iio driver updates Stephen Boyd
2020-07-29  9:20     ` Stephen Boyd

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