Messages in this thread | | | Date | Thu, 24 Mar 2022 11:24:26 +0200 | From | Andy Shevchenko <> | Subject | Re: [PATCH v1 1/4] spidev: Do not use atomic bit operations when allocating minor |
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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
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