Re: [HACKERS] Atomics for heap_parallelscan_nextpage()

Andres Freund <andres@anarazel.de> writes:
> On 2017-08-16 16:20:28 +0300, Heikki Linnakangas wrote:
> +    pg_atomic_write_u64(&target->phs_nallocated, 0);

> It's not ok to initialize an atomic with pg_atomic_write_u64 - works
> well enough for "plain" atomics, but the fallback implementation isn't
> ok with it. You're probably going to get a failure on the respective
> buildfarm animal soon.

Indeed, gaur fails with

2017-08-16 17:09:38.315 EDT [13043:11] PANIC:  stuck spinlock detected at pg_at\
omic_compare_exchange_u64_impl, atomics.c:196
2017-08-16 17:09:38.315 EDT [13043:12] STATEMENT:  select count(*) from a_star;
2017-08-16 17:09:40.350 EDT [12437:3] LOG:  server process (PID 13043) was term\
inated by signal 6
2017-08-16 17:09:40.350 EDT [12437:4] DETAIL:  Failed process was running: sele\
ct count(*) from a_star;

and I'm sure pademelon will fail once it gets to that.  I thought we
had other buildfarm animals testing the fallback path, though?
        regards, tom lane