Re: [BUGS] Assertion failure on reload of GUC_SUPERUSER_ONLY parms

[Tom Lane]

Simon Riggs  writes:
> It looks to me like the correct fix would be to use
> GetUserIdAndContext() instead, though I would suggest inventing
> GetUserIdIfAny() which would skip the assertion test for use in
> superuser().

You are thinking at the wrong abstraction level.  Even to ask if
the user is superuser is inappropriate in the postmaster, since
there is no user.  So I think the bug is that GetConfigOption
is calling superuser() when it is now possible for it to be used
in the postmaster.

The quick & dirty fix would be to add IsUnderPostmaster to the
check in GetConfigOption.  Or we could refactor things so that
the GUC_SUPERUSER_ONLY check is applied at some higher level;
but that's probably more work than it's worth.

It looks to me like the pstrdup that was added in guc-file.l
represents a permanent memory leak in the postmaster, too :-(

regards, tom lane

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[BUGS] Assertion failure on reload of GUC_SUPERUSER_ONLY parms

[Simon Riggs]

TRAP: BadState("!(((bool) ((CurrentUserId) != ((Oid) 0", File:
"miscinit.c", Line: 295)

Gabriele Bartolini originally reported this to me as a bug in Hot
Standby, though I have now been able to reproduce in CVS head. We were
just unlucky enough to hit it while doing thorough HS testing.

backtrace
#0  0x2b7beafd2b45 in raise () from /lib64/libc.so.6
#1  0x2b7beafd40e0 in abort () from /lib64/libc.so.6
#2  0x006c016d in ExceptionalCondition (
conditionName=, errorType=, 
fileName=, lineNumber=)
at assert.c:57
#3  0x006ccf4d in GetUserId () at miscinit.c:295
#4  0x006db1b9 in superuser () at superuser.c:48
#5  0x006d5a2b in GetConfigOption (name=0xb2b6e8 "log_filename")
at guc.c:5226
#6  0x006d8a2c in ProcessConfigFile (context=PGC_SIGHUP)
at guc-file.l:319
#7  0x005e49e2 in SIGHUP_handler (
postgres_signal_arg=) at postmaster.c:2062
#8  
#9  0x2b7beb060bc3 in select () from /lib64/libc.so.6
#10 0x005e1bf7 in ServerLoop () at postmaster.c:1360
#11 0x005e2b14 in PostmasterMain (argc=3, argv=0xb246a0)
at postmaster.c:1065

It turns out that when you modify a GUC_SUPERUSER_ONLY parameter, such
as log_filename, in postgresql.conf and then reload you will get the
assertion failure.

It looks to me like the correct fix would be to use
GetUserIdAndContext() instead, though I would suggest inventing
GetUserIdIfAny() which would skip the assertion test for use in
superuser().

-- 
 Simon Riggs   www.2ndQuadrant.com


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