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Nathan Bossart c9265ae80b Avoid calling proc_exit() in processes forked by system().
The SIGTERM handler for the startup process immediately calls
proc_exit() for the duration of the restore_command, i.e., a call
to system().  This system() call forks a new process to execute the
shell command, and this child process inherits the parent's signal
handlers.  If both the parent and child processes receive SIGTERM,
both will attempt to call proc_exit().  This can end badly.  For
example, both processes will try to remove themselves from the
PGPROC shared array.

To fix this problem, this commit adds a check in
StartupProcShutdownHandler() to see whether MyProcPid == getpid().
If they match, this is the parent process, and we can proc_exit()
like before.  If they do not match, this is a child process, and we
just emit a message to STDERR (in a signal safe manner) and
_exit(), thereby skipping any problematic exit callbacks.

This commit also adds checks in proc_exit(), ProcKill(), and
AuxiliaryProcKill() that verify they are not being called within
such child processes.

Suggested-by: Andres Freund
Reviewed-by: Thomas Munro, Andres Freund
Discussion: https://postgr.es/m/Y9nGDSgIm83FHcad%40paquier.xyz
Discussion: https://postgr.es/m/20230223231503.GA743455%40nathanxps13
Backpatch-through: 11
2023-10-17 10:42:06 -05:00
config Use --strip-unneeded when stripping static libraries with GNU strip. 2023-04-20 18:12:48 -04:00
contrib Dissociate btequalimage() from interval_ops, ending its deduplication. 2023-10-14 16:33:54 -07:00
doc Update the documentation on recovering from (M)XID exhaustion. 2023-10-16 13:14:07 -04:00
src Avoid calling proc_exit() in processes forked by system(). 2023-10-17 10:42:06 -05:00
.cirrus.star ci: Prepare to make compute resources for CI configurable 2023-08-23 15:15:29 -07:00
.cirrus.tasks.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:29 -07:00
.cirrus.yml ci: Make compute resources for CI configurable 2023-08-23 15:15:29 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.editorconfig Add .editorconfig 2019-12-18 09:13:13 +01:00
.git-blame-ignore-revs Backpatch addition of .git-blame-ignore-revs 2022-08-05 19:36:24 +02:00
.gitattributes Remove trailing whitespace from *.sgml files. 2022-04-20 11:04:49 -04:00
.gitignore Add portlock directory to .gitignore 2022-11-26 07:47:01 -05:00
aclocal.m4 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Stamp 15.4. 2023-08-07 16:08:18 -04:00
configure.ac Stamp 15.4. 2023-08-07 16:08:18 -04:00
COPYRIGHT Update copyright for 2023 2023-01-02 15:00:37 -05:00
GNUmakefile.in Remove temporary portlock directory during make [dist]clean. 2022-11-26 10:30:46 -05:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Dynamically find correct installation docs in Makefile. 2022-01-19 14:48:25 +01:00
README Canonicalize some URLs 2020-02-10 20:47:50 +01:00
README.git Canonicalize some URLs 2020-02-10 20:47:50 +01:00

PostgreSQL Database Management System
=====================================

This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces, many of which are listed here:

	https://www.postgresql.org/download/

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.