Re: Wait free LW_SHARED acquisition - v0.2

Hi,

On 2013-09-27 00:55:45 +0200, Andres Freund wrote:
> So what's todo? The file header tells us:
> * - revive pure-spinlock implementation
> * - abstract away atomic ops, we really only need a few.
> * - CAS
> * - LOCK XADD
> * - convert PGPROC->lwWaitLink to ilist.h slist or even dlist.
> * - remove LWLockWakeup dealing with MyProc
> * - overhaul the mask offsets, make SHARED/EXCLUSIVE_LOCK_MASK wider, MAX_BACKENDS

So, here's the next version of this patchset:
1) I've added an abstracted atomic ops implementation. Needs a fair
amount of work, also submitted as a separate CF entry. (Patch 1 & 2)
2) I've converted PGPROC->lwWaiting into a dlist. That makes a fair bit
of code easier to read and reduces the size of the patchset. Also
fixes a bug in the xlog-scalability code. (Patch 3)
3) Alvaro and I updated the comments in lwlock.c. (Patch 4)

I think 2) should be committable pretty soon. It's imo a pretty clear
win in readability. 1) will need a good bit of more work.

With regard to the scalable lwlock work, what's most needed now is a
good amount of testing.

Please note that you need to 'autoreconf' after applying the patchset. I
don't have a compatible autoconf version on this computer causing the
diff to be humongous if I include those changes.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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