Re: Yet another way for pg_ctl stop to fail on Windows

Hello Noah,

08.09.2024 19:53, Noah Misch wrote:
> I see Microsoft suggests WaitNamedPipeA() as opposed to just polling.
> WaitNamedPipeA() should be more responsive.  Given how rare this has been, it
> likely doesn't matter whether we use WaitNamedPipeA() or polling.  I'd lean
> toward whichever makes the code simpler, probably polling.
>
>> So if we aim to not only fix "pg_ctl stop", but to make pgkill() robust,
>> it's the way to go, IMHO. I'm not sure about an infinite loop they show,
>> I'd vote for a loop with the same characteristics as in
>> pgwin32_open_handle().
> I agree with bounding the total time of each kill(), like
> pgwin32_open_handle() does for open().

While investigating a recent buildfarm failure [1] (which also happened
before: [2]):
# # --- C:/prog/bf/root/HEAD/pgsql/src/test/regress/expected/misc_functions.out 2026-04-08 01:57:31.191354200 +0000
# # +++ C:/prog/bf/root/HEAD/pgsql.build/testrun/pg_upgrade/002_pg_upgrade/data/results/misc_functions.out 2026-04-24 
02:45:42.446717500 +0000
# # @@ -316,9 +316,10 @@
# #  -- permissions are set properly.
# #  --
# #  SELECT pg_log_backend_memory_contexts(pg_backend_pid());
# # +WARNING:  could not send signal to process 3940: Invalid argument
# #   pg_log_backend_memory_contexts
# #  --------------------------------
# # - t
# # + f
# #  (1 row)
# #
# #  SELECT pg_log_backend_memory_contexts(pid) FROM pg_stat_activity
# # @@ -347,9 +348,10 @@
# #
# #  SET ROLE regress_log_memory;
# #  SELECT pg_log_backend_memory_contexts(pg_backend_pid());
# # +WARNING:  could not send signal to process 3940: Invalid argument
# #   pg_log_backend_memory_contexts
# #  --------------------------------
# # - t
# # + f
# #  (1 row)
# #
# #  RESET ROLE;
# # 1 of 248 tests failed.
# # The differences that caused some tests to fail can be viewed in the file 
"C:/prog/bf/root/HEAD/pgsql.build/testrun/pg_upgrade/002_pg_upgrade/data/regression.diffs".
# # A copy of the test summary that you see above is saved in the file 
"C:/prog/bf/root/HEAD/pgsql.build/testrun/pg_upgrade/002_pg_upgrade/data/regression.out".
# ------------------------------------
# Looks like you failed 1 test of 20.

I've managed to reproduced it locally, by running five
pg_upgrade/002_pg_upgrade tests (with
"SELECT pg_log_backend_memory_contexts(pg_backend_pid());" x100 in
misc_functions.sql) concurrently on one-core VM:
iteration 3
1/5 postgresql:pg_upgrade_5 / pg_upgrade_5/002_pg_upgrade OK              184.42s   5 subtests passed
2/5 postgresql:pg_upgrade_1 / pg_upgrade_1/002_pg_upgrade ERROR           184.79s   exit status 1

pg_upgrade_1\002_pg_upgrade\log\002_pg_upgrade_old_node.log:
2026-04-26 13:13:44.238 UTC client backend[688] pg_regress/misc_functions WARNING:  could not send signal to process 
688: Invalid argument

With the logging added inside pgkill():
@@ -89,6 +93,9 @@ pgkill(int pid, int sig)
                         errno = EPERM;
                         return -1;
                 default:
+#ifndef FRONTEND
+elog(LOG, "!!!pgkill| CallNamedPipe() returned %d", GetLastError());
+#endif
                         errno = EINVAL;         /* unexpected */
                         return -1;
         }

and backtrace_functions = 'pgkill', I could see
2026-04-26 13:13:44.237 UTC client backend[688] pg_regress/misc_functions LOG:  !!!pgkill| CallNamedPipe() returned 231
2026-04-26 13:13:44.237 UTC client backend[688] pg_regress/misc_functions BACKTRACE:
     pgkill+0x15f [0x7ff6c05279ef] [C:\src\postgresql\src\port\kill.c:103]
     SendProcSignal+0xb1 [0x7ff6c03202e1] [C:\src\postgresql\src\backend\storage\ipc\procsignal.c:341]
     pg_log_backend_memory_contexts+0x7b [0x7ff6c040df1b] [C:\src\postgresql\src\backend\utils\adt\mcxtfuncs.c:301]
     ExecInterpExpr+0x684 [0x7ff6c00ec264] [C:\src\postgresql\src\backend\executor\execExprInterp.c:630]
...

That is, pg_log_backend_memory_contexts(() fails due to the same
ERROR_PIPE_BUSY.

Moreover, I can see other instances of this error in the log, which go
unnoticed:
2026-04-26 13:12:19.049 UTC client backend[2948] pg_regress/subselect LOG:  !!!pgkill| CallNamedPipe() returned 231
2026-04-26 13:12:19.049 UTC client backend[2948] pg_regress/subselect BACKTRACE:
     pgkill+0x15f [0x7ff6c05279ef] [C:\src\postgresql\src\port\kill.c:103]
     SendProcSignal+0xb1 [0x7ff6c03202e1] [C:\src\postgresql\src\backend\storage\ipc\procsignal.c:341]
     SICleanupQueue+0x1e1 [0x7ff6c03252b1] [C:\src\postgresql\src\backend\storage\ipc\sinvaladt.c:677]
     SIInsertDataEntries+0x91 [0x7ff6c0325511] [C:\src\postgresql\src\backend\storage\ipc\sinvaladt.c:411]
     AtEOXact_Inval+0x86 [0x7ff6c04b0636] [C:\src\postgresql\src\backend\utils\cache\inval.c:1225]
     CommitTransaction+0x2b4 [0x7ff6bffa5604] [C:\src\postgresql\src\backend\access\transam\xact.c:2477]
     CommitTransactionCommandInternal+0x8e [0x7ff6bffa588e] [C:\src\postgresql\src\backend\access\transam\xact.c:3253]
     CommitTransactionCommand+0x9 [0x7ff6bffa57e9] [C:\src\postgresql\src\backend\access\transam\xact.c:3213]
     RemoveTempRelationsCallback+0x6a [0x7ff6bfff51fa] [C:\src\postgresql\src\backend\catalog\namespace.c:4710]
     proc_exit_prepare+0xc6 [0x7ff6c03178d6] [C:\src\postgresql\src\backend\storage\ipc\ipc.c:199]
     proc_exit+0x56 [0x7ff6c03177c6] [C:\src\postgresql\src\backend\storage\ipc\ipc.c:155]
     PostgresMain+0xd9a [0x7ff6c034e2ea] [C:\src\postgresql\src\backend\tcop\postgres.c:5091]
     BackendMain+0xd5 [0x7ff6c034acb5] [C:\src\postgresql\src\backend\tcop\backend_startup.c:124]
...
2026-04-26 13:12:45.010 UTC client backend[8104] pg_regress/replica_identity LOG:  !!!pgkill| CallNamedPipe() returned 231
2026-04-26 13:12:45.010 UTC client backend[8104] pg_regress/replica_identity BACKTRACE:
     pgkill+0x15f [0x7ff6c05279ef] [C:\src\postgresql\src\port\kill.c:103]
     SendProcSignal+0xb1 [0x7ff6c03202e1] [C:\src\postgresql\src\backend\storage\ipc\procsignal.c:341]
     SICleanupQueue+0x1e1 [0x7ff6c03252b1] [C:\src\postgresql\src\backend\storage\ipc\sinvaladt.c:677]
     SIInsertDataEntries+0x91 [0x7ff6c0325511] [C:\src\postgresql\src\backend\storage\ipc\sinvaladt.c:411]
     AtInplace_Inval+0x67 [0x7ff6c04b0727] [C:\src\postgresql\src\backend\utils\cache\inval.c:1270]
     heap_inplace_update_and_unlock+0x266 [0x7ff6bff2a366] [C:\src\postgresql\src\backend\access\heap\heapam.c:6591]
     systable_inplace_update_finish+0x20 [0x7ff6bff4c160] [C:\src\postgresql\src\backend\access\index\genam.c:904]
     index_update_stats+0x21e [0x7ff6bffefefe] [C:\src\postgresql\src\backend\catalog\index.c:2982]
     index_build+0x2fc [0x7ff6bffed2fc] [C:\src\postgresql\src\backend\catalog\index.c:3180]
     index_create+0xc05 [0x7ff6bffef035] [C:\src\postgresql\src\backend\catalog\index.c:1291]
     DefineIndex+0x12fc [0x7ff6c006544c] [C:\src\postgresql\src\backend\commands\indexcmds.c:1265]
     ProcessUtilitySlow+0x924 [0x7ff6c0358524] [C:\src\postgresql\src\backend\tcop\utility.c:1566]
     standard_ProcessUtility+0x9f0 [0x7ff6c0359ec0] [C:\src\postgresql\src\backend\tcop\utility.c:1078]
     ProcessUtility+0x70 [0x7ff6c0357aa0] [C:\src\postgresql\src\backend\tcop\utility.c:531]
     ProcessUtilitySlow+0x3a0 [0x7ff6c0357fa0] [C:\src\postgresql\src\backend\tcop\utility.c:1262]
     standard_ProcessUtility+0x9f0 [0x7ff6c0359ec0] [C:\src\postgresql\src\backend\tcop\utility.c:1078]
     ProcessUtility+0x70 [0x7ff6c0357aa0] [C:\src\postgresql\src\backend\tcop\utility.c:531]


[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=drongo&dt=2026-04-24%2001%3A26%3A26
[2] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=drongo&dt=2025-09-26%2018%3A15%3A06

Best regards,
Alexander