Re: xlc atomics

On Mon, Feb 15, 2016 at 06:33:42PM +0100, Andres Freund wrote:
> On 2016-02-15 12:11:29 -0500, Noah Misch wrote:
> > These suggested OidGenLock wasn't doing its job.  I've seen similar symptoms
> > around WALInsertLocks with "IBM XL C/C++ for Linux, V13.1.2 (5725-C73,
> > 5765-J08)" for ppc64le.  The problem is generic-xlc.h
> > pg_atomic_compare_exchange_u32_impl() issuing __isync() before
> > __compare_and_swap().  __isync() shall follow __compare_and_swap(); see our
> > own s_lock.h, its references, and other projects' usage:
> 
> Ugh. You're right! It's about not moving code before the stwcx...
> 
> Do you want to add the new test (no objection, curious), or is that more
> for testing?

The patch's test would join PostgreSQL indefinitely.