Horton

"could not reattach to shared memory" on buildfarm member dory

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stephen Frost <sfrost@snowman.net>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2018-04-23T21:10:20Z
Lists: pgsql-hackers 
So far, dory has failed three times with essentially identical symptoms:

2018-04-23 19:57:10.624 GMT [2240] FATAL:  could not reattach to shared memory (key=0000000000000190, addr=00000000018E0000): error code 487
2018-04-23 15:57:10.657 EDT [8836] ERROR:  lost connection to parallel worker
2018-04-23 15:57:10.657 EDT [8836] STATEMENT:  select count(*) from tenk1 group by twenty;
2018-04-23 15:57:10.660 EDT [3820] LOG:  background worker "parallel worker" (PID 2240) exited with exit code 1

Now how can this be?  We've successfully reserved and released the address
range we want to use, so it *should* be free at the instant we try to map.

Another thing that seems curious, though it may just be an artifact of
not having many data points yet, is that these failures all occurred
during pg_upgradecheck.  You'd think the "check" and "install-check"
steps would be equally vulnerable to the failure.

I guess the good news is that we're seeing this in a reasonably
reproducible fashion, so there's some hope of digging down to find
out the actual cause.

			regards, tom lane

Commits

  1. Avoid "could not reattach" by providing space for concurrent allocation.

  2. Assert that pgwin32_signal_initialize() has been called early enough.

  3. Remove investigative code for can't-reattach-to-shared-memory errors.

  4. Does it help to wait before reattaching?

  5. Map and unmap the shared memory block before risking VirtualFree.

  6. Further effort at preventing memory map dump from affecting the results.

  7. Remove Windows module-list-dumping code.

  8. Dump full memory maps around failing Windows reattach code.

  9. Get still more info about Windows can't-reattach-to-shared-memory errors.

  10. Get more info about Windows can't-reattach-to-shared-memory errors.

  11. Try to get some info about Windows can't-reattach-to-shared-memory errors.