main() says:
/*
* Fire up essential subsystems: error and memory management
*
* Code after this point is allowed to use elog/ereport, though
* localization of messages may not work right away, and messages won't
go
* anywhere but stderr until GUC settings get loaded.
*/
MemoryContextInit();
However, appending elog(ERROR, "whoops") breaks like:
$ initdb -D discard_me
FATAL: whoops
PANIC: proc_exit() called in child process
no data was returned by command ""/home/nm/sw/nopath/pghead/bin/postgres" -V"
child process was terminated by signal 6: Aborted
So does the ereport(FATAL) in ClosePostmasterPorts(). The "called in child
process" check (added in commit 97550c0 of 2023-10) reads MyProcPid, which we
set later. Three ways to fix this:
1. Call InitProcessGlobals() earlier. This could also reduce the total call
sites from 3 to 2 (main() and post-fork).
2. Move MyProcPid init out of InitProcessGlobals(), to main() and post-fork.
This has less to go wrong in back branches. While probably irrelevant,
this avoids calling pg_prng_strong_seed() in processes that will exit after
help() or GucInfoMain().
3. Revert 97550c0, as commit 3b00fdb anticipated.
I don't think the choice matters much, so here is (2).
Author: Noah Misch <[email protected]>
Commit: Noah Misch <[email protected]>
Fix elog(FATAL) before PostmasterMain() or just after fork().
Since commit 97550c0711972a9856b5db751539bbaf2f88884c, these failed with
"PANIC: proc_exit() called in child process" due to uninitialized or
stale MyProcPid. That was reachable if close() failed in
ClosePostmasterPorts() or setlocale(category, "C") failed, both
unlikely. Back-patch to v13 (all supported versions).
Reviewed by FIXME.
Discussion: https://postgr.es/m/FIXME
diff --git a/src/backend/main/main.c b/src/backend/main/main.c
index 3acb46b..e286810 100644
--- a/src/backend/main/main.c
+++ b/src/backend/main/main.c
@@ -109,6 +109,7 @@ main(int argc, char *argv[])
* localization of messages may not work right away, and messages won't
go
* anywhere but stderr until GUC settings get loaded.
*/
+ MyProcPid = getpid();
MemoryContextInit();
/*
diff --git a/src/backend/postmaster/fork_process.c
b/src/backend/postmaster/fork_process.c
index 5e42a74..b3010e3 100644
--- a/src/backend/postmaster/fork_process.c
+++ b/src/backend/postmaster/fork_process.c
@@ -19,6 +19,7 @@
#include <unistd.h>
#include "libpq/pqsignal.h"
+#include "miscadmin.h"
#include "postmaster/fork_process.h"
#ifndef WIN32
@@ -66,6 +67,7 @@ fork_process(void)
if (result == 0)
{
/* fork succeeded, in child */
+ MyProcPid = getpid();
#ifdef LINUX_PROFILE
setitimer(ITIMER_PROF, &prof_itimer, NULL);
#endif
diff --git a/src/backend/postmaster/postmaster.c
b/src/backend/postmaster/postmaster.c
index ce00f40..f0f9c66 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -1899,14 +1899,13 @@ ClosePostmasterPorts(bool am_syslogger)
/*
- * InitProcessGlobals -- set MyProcPid, MyStartTime[stamp], random seeds
+ * InitProcessGlobals -- set MyStartTime[stamp], random seeds
*
* Called early in the postmaster and every backend.
*/
void
InitProcessGlobals(void)
{
- MyProcPid = getpid();
MyStartTimestamp = GetCurrentTimestamp();
MyStartTime = timestamptz_to_time_t(MyStartTimestamp);
diff --git a/src/port/pqsignal.c b/src/port/pqsignal.c
index 6ca2d4e..bdaa9f1 100644
--- a/src/port/pqsignal.c
+++ b/src/port/pqsignal.c
@@ -74,8 +74,7 @@ static volatile pqsigfunc pqsignal_handlers[PG_NSIG];
/*
* Except when called with SIG_IGN or SIG_DFL, pqsignal() sets up this function
* as the handler for all signals. This wrapper handler function checks that
- * it is called within a process that the server knows about (i.e., any process
- * that has called InitProcessGlobals(), such as a client backend), and not a
+ * it is called within a process that knew to maintain MyProcPid, and not a
* child process forked by system(3), etc. This check ensures that such child
* processes do not modify shared memory, which is often detrimental. If the
* check succeeds, the function originally provided to pqsignal() is called.
