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Tom Lane 7309e75fa9 Fix race condition in our Windows signal emulation.
pg_signal_dispatch_thread() responded to the client (signal sender)
and disconnected the pipe before actually setting the shared variables
that make the signal visible to the backend process's main thread.
In the worst case, it seems, effective delivery of the signal could be
postponed for as long as the machine has any other work to do.

To fix, just move the pg_queue_signal() call so that we do it before
responding to the client.  This essentially makes pgkill() synchronous,
which is a stronger guarantee than we have on Unix.  That may be
overkill, but on the other hand we have not seen comparable timing bugs
on any Unix platform.

While at it, add some comments to this sadly underdocumented code.

Problem diagnosis and fix by Amit Kapila; I just added the comments.

Back-patch to all supported versions, as it appears that this can cause
visible NOTIFY timing oddities on all of them, and there might be
other misbehavior due to slow delivery of other signals.

Discussion: https://postgr.es/m/32745.1575303812@sss.pgh.pa.us
2019-12-09 15:03:52 -05:00
config configure: Update python search order 2019-09-08 13:45:13 -04:00
contrib Ensure maxlen is at leat 1 in dict_int 2019-12-03 18:43:15 +01:00
doc Document search_path security with untrusted dbowner or CREATEROLE. 2019-12-08 11:06:31 -08:00
src Fix race condition in our Windows signal emulation. 2019-12-09 15:03:52 -05:00
.dir-locals.el Update Emacs configuration 2013-08-13 20:08:44 -04:00
.gitattributes gitattributes: Ignore time zone data files for whitespace checks 2014-07-22 00:12:28 -04:00
.gitignore Add /config.cache to .gitignore in back branches 2017-02-25 13:04:22 -05:00
aclocal.m4 Back-patch updated thread flags tests into 9.4 and 9.5. 2018-11-19 14:24:52 -05:00
configure Stamp 9.4.25. 2019-11-11 17:13:41 -05:00
configure.in Stamp 9.4.25. 2019-11-11 17:13:41 -05:00
COPYRIGHT Update copyright for 2019 2019-01-02 12:44:25 -05:00
GNUmakefile.in Add TAP tests for client programs 2014-04-14 21:33:46 -04:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Fix non-GNU makefiles for AIX make. 2017-11-30 00:57:32 -08:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
README.git Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00

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/.