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Tom Lane 1750612224 Avoid SIGBUS on Linux when a DSM memory request overruns tmpfs. 
On Linux, shared memory segments created with shm_open() are backed by
swap files created in tmpfs.  If the swap file needs to be extended,
but there's no tmpfs space left, you get a very unfriendly SIGBUS trap.
To avoid this, force allocation of the full request size when we create
the segment.  This adds a few cycles, but none that we wouldn't expend
later anyway, assuming the request isn't hugely bigger than the actual
need.

Make this code #ifdef __linux__, because (a) there's not currently a
reason to think the same problem exists on other platforms, and (b)
applying posix_fallocate() to an FD created by shm_open() isn't very
portable anyway.

Back-patch to 9.4 where the DSM code came in.

Thomas Munro, per a bug report from Amul Sul

Discussion: https://postgr.es/m/1002664500.12301802.1471008223422.JavaMail.yahoo@mail.yahoo.com
 		2017-09-25 16:09:20 -04:00
config Absorb -D_USE_32BIT_TIME_T switch from Perl, if relevant. 2017-08-14 11:48:59 -04:00
contrib Remove bogus line from comment. 2017-08-17 11:19:43 -04:00
doc Support building with Visual Studio 2017 2017-09-25 08:08:52 -04:00
src Avoid SIGBUS on Linux when a DSM memory request overruns tmpfs. 2017-09-25 16:09:20 -04:00
.dir-locals.el emacs: Set indent-tabs-mode in perl-mode 2015-04-12 23:53:23 -04:00
.gitattributes Fix whitespace and remove obsolete gitattributes entry 2016-03-13 16:03:13 -04:00
.gitignore Add .gitignore entries for AIX-specific intermediate build artifacts. 2015-07-08 20:44:22 -04:00
COPYRIGHT Update copyright for 2017 2017-01-03 12:37:53 -05:00
GNUmakefile.in Fix distclean/maintainer-clean targets to remove top-level tmp_install dir. 2015-05-13 18:48:05 -04:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Prevent passing down MAKELEVEL/MAKEFLAGS from non-GNU make to GNU make. 2017-08-09 12:06:08 -04:00
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
aclocal.m4 Replace our hacked version of ax_pthread.m4 with latest upstream version. 2015-07-08 20:36:06 +03:00
configure Avoid SIGBUS on Linux when a DSM memory request overruns tmpfs. 2017-09-25 16:09:20 -04:00
configure.in Avoid SIGBUS on Linux when a DSM memory request overruns tmpfs. 2017-09-25 16:09:20 -04:00

README 

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/.