Re: Re: [COMMITTERS] pgsql: Allow Pin/UnpinBuffer to operate in a lockfree manner. - Mailing list pgsql-hackers

From Andres Freund
Subject Re: Re: [COMMITTERS] pgsql: Allow Pin/UnpinBuffer to operate in a lockfree manner.
Date
Msg-id 20160412040335.7melgsixigrhr656@alap3.anarazel.de
Whole thread Raw
In response to Re: Re: [COMMITTERS] pgsql: Allow Pin/UnpinBuffer to operate in a lockfree manner.  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
On 2016-04-11 23:59:21 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > Will fix (both initialization and use of pg_atomic_fetch_or_u32), and
> > expand the documentation on why only atomic read/write are supposed to
> > be used.
> 
> FWIW, I'd vote against adding a SpinLockInit there.

Well, it'd not be a SpinLockInit, but a pg_atomic_init_u32(), but ...

> What it would mostly
> do is prevent noticing future mistakes of the same ilk.  It would be
> better no doubt if we didn't have to rely on a nearly-dead platform
> to detect this; but having such detection of a performance bug is better
> than having no detection.

Ok, works for me as well. I guess it'd be useful to add a "modern"
animal that disables spinlocks & atomics...

- Andres



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