Re: Refactoring backend fork+exec code

Hello Heikki,

01.12.2023 23:44, Heikki Linnakangas wrote:
>
>> With memset(param, 0, sizeof(*param)); added at the beginning of
>> save_backend_variables(), server starts successfully, but then
>> `make check` fails with other Valgrind error.
>
> That's actually a pre-existing issue, I'm seeing that even on unpatched 'master'.

Thank you for fixing that!

Yes, I had discovered it before, but yesterday I decided to check whether
your patches improve the situation...

What bothered me additionally, is an error detected after server start. I
couldn't see it without the patches applied. I mean, on HEAD I now see
`make check` passing, but with the patches it fails:
...
# parallel group (20 tests):  interval date numerology polygon box macaddr8 macaddr multirangetypes line timestamp 
timetz timestamptz time circle strings lseg inet md5 path point
not ok 22    + strings                                  1048 ms
# (test process exited with exit code 2)
not ok 23    + md5                                      1052 ms
# (test process exited with exit code 2)
...
src/test/regress/log/postmaster.log contains:
==00:00:00:30.730 1713480== Syscall param write(buf) points to uninitialised byte(s)
==00:00:00:30.730 1713480==    at 0x5245A37: write (write.c:26)
==00:00:00:30.730 1713480==    by 0x51BBF6C: _IO_file_write@@GLIBC_2.2.5 (fileops.c:1180)
==00:00:00:30.730 1713480==    by 0x51BC84F: new_do_write (fileops.c:448)
==00:00:00:30.730 1713480==    by 0x51BC84F: _IO_new_file_xsputn (fileops.c:1254)
==00:00:00:30.730 1713480==    by 0x51BC84F: _IO_file_xsputn@@GLIBC_2.2.5 (fileops.c:1196)
==00:00:00:30.730 1713480==    by 0x51B1056: fwrite (iofwrite.c:39)
==00:00:00:30.730 1713480==    by 0x5540CF: internal_forkexec (postmaster.c:4526)
==00:00:00:30.730 1713480==    by 0x5543C0: bgworker_forkexec (postmaster.c:5624)
==00:00:00:30.730 1713480==    by 0x555477: do_start_bgworker (postmaster.c:5665)
==00:00:00:30.730 1713480==    by 0x555738: maybe_start_bgworkers (postmaster.c:5928)
==00:00:00:30.730 1713480==    by 0x556072: process_pm_pmsignal (postmaster.c:5080)
==00:00:00:30.730 1713480==    by 0x556610: ServerLoop (postmaster.c:1761)
==00:00:00:30.730 1713480==    by 0x557BE2: PostmasterMain (postmaster.c:1469)
==00:00:00:30.730 1713480==    by 0x47216B: main (main.c:198)
==00:00:00:30.730 1713480==  Address 0x1ffeffd8c0 is on thread 1's stack
==00:00:00:30.730 1713480==  in frame #4, created by internal_forkexec (postmaster.c:4482)
==00:00:00:30.730 1713480==
...
2023-12-02 05:14:30.751 MSK client backend[1713740] pg_regress/rangetypes FATAL:  terminating connection due to 
unexpected postmaster exit
2023-12-02 05:14:31.033 MSK client backend[1713734] pg_regress/numeric FATAL:  postmaster exited during a parallel 
transaction
TRAP: failed Assert("!IsTransactionOrTransactionBlock()"), File: "pgstat.c", Line: 591, PID: 1713734

I haven't looked deeper yet, but it seems that we see two issues here (and
Assert is not directly caused by the patches set.)

Best regards,
Alexander