From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Mark Brown <broonie@kernel.org>
Cc: linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 1/4] spidev: Do not use atomic bit operations when allocating minor
Date: Thu, 24 Mar 2022 11:24:26 +0200 [thread overview]
Message-ID: <Yjw4yjgordnSo+7M@smile.fi.intel.com> (raw)
In-Reply-To: <YjtvsYs+x3LRaLVP@sirena.org.uk>
On Wed, Mar 23, 2022 at 07:06:25PM +0000, Mark Brown wrote:
> On Wed, Mar 23, 2022 at 07:22:52PM +0200, Andy Shevchenko wrote:
> > On Wed, Mar 23, 2022 at 04:39:01PM +0000, Mark Brown wrote:
>
> > > There's no *need* but the __ looks suspicious... what's the upside
> > > here?
>
> > It's exactly what is written in the commit message
>
> > __*_bit() are non-atomic
> > *_bit() are atomic
>
> > Since they are wrapped by mutex, the atomic ones are not needed.
>
> Yes, it's not needed but what meaningful harm does it do?
There are basically two points:
1) in one driver the additional lock may not be influential, but
if many drivers will do the same, it will block CPUs for no
purpose;
2) derived from the above, if one copies'n'pastes the code, esp.
using spin locks, it may become an unneeded code and performance
degradation.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-03-24 9:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 14:02 Andy Shevchenko
2022-03-23 14:02 ` [PATCH v1 2/4] spidev: Convert BUILD_BUG_ON() to static_assert() Andy Shevchenko
2022-03-23 14:02 ` [PATCH v1 3/4] spidev: Replace ACPI specific code by device_get_match_data() Andy Shevchenko
2022-03-23 14:02 ` [PATCH v1 4/4] spidev: Replace OF specific code by device property API Andy Shevchenko
2022-03-23 16:39 ` [PATCH v1 1/4] spidev: Do not use atomic bit operations when allocating minor Mark Brown
2022-03-23 17:22 ` Andy Shevchenko
2022-03-23 19:06 ` Mark Brown
2022-03-24 9:24 ` Andy Shevchenko [this message]
2022-03-24 14:28 ` Mark Brown
2022-03-25 11:09 ` Andy Shevchenko
2022-03-26 1:29 ` Yury Norov
2022-03-25 12:44 ` Andy Shevchenko
2022-03-25 13:26 ` Mark Brown
2022-03-25 13:44 ` Andy Shevchenko
2022-04-05 9:32 ` (subset) " Mark Brown
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