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Thomas Munro 2019e6ecfa Block signals while allocating DSM memory. 
On Linux, we call posix_fallocate() on shm_open()'d memory to avoid
later potential SIGBUS (see commit 899bd785).

Based on field reports of systems stuck in an EINTR retry loop there,
there, we made it possible to break out of that loop via slightly odd
coding where the CHECK_FOR_INTERRUPTS() call was somewhat removed from
the loop (see commit 422952ee).

On further reflection, that was not a great choice for at least two
reasons:

1.  If interrupts were held, the CHECK_FOR_INTERRUPTS() would do nothing
and the EINTR error would be surfaced to the user.

2.  If EINTR was reported but neither QueryCancelPending nor
ProcDiePending was set, then we'd dutifully retry, but with a bit more
understanding of how posix_fallocate() works, it's now clear that you
can get into a loop that never terminates.  posix_fallocate() is not a
function that can do some of the job and tell you about progress if it's
interrupted, it has to undo what it's done so far and report EINTR, and
if signals keep arriving faster than it can complete (cf recovery
conflict signals), you're stuck.

Therefore, for now, we'll simply block most signals to guarantee
progress.  SIGQUIT is not blocked (see InitPostmasterChild()), because
its expected handler doesn't return, and unblockable signals like
SIGCONT are not expected to arrive at a high rate.  For good measure,
we'll include the ftruncate() call in the blocked region, and add a
retry loop.

Back-patch to all supported releases.

Reported-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reported-by: Nicola Contu <nicola.contu@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20220701154105.jjfutmngoedgiad3%40alvherre.pgsql
 		2022-07-14 17:48:32 +12:00
config Suppress warning about stack_base_ptr with late-model GCC. 2022-02-17 22:45:34 -05:00
contrib CREATE INDEX: use the original userid for more ACL checks. 2022-06-25 09:07:44 -07:00
doc doc: Fix inconsistent quotes in some jsonb fields 2022-07-11 10:56:48 +09:00
src Block signals while allocating DSM memory. 2022-07-14 17:48:32 +12:00
.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 Add list of ignorable pgindent commits for git-blame. 2021-06-22 09:06:32 -07:00
.gitattributes gitattributes: Add new entry to silence whitespace error 2021-06-05 07:57:31 +02:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
COPYRIGHT Update copyright for 2022 2022-01-07 19:04:56 -05:00
GNUmakefile.in add missing tag from commit b8c4261e5e 2021-07-01 15:47:47 -04:00
HISTORY Canonicalize some URLs 2020-02-10 20:47:50 +01:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:36:21 +12:00
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
aclocal.m4 Probe $PROVE not $PERL while checking for modules needed by TAP tests. 2021-11-22 12:54:52 -05:00
configure Stamp 14.4. 2022-06-13 16:04:05 -04:00
configure.ac Stamp 14.4. 2022-06-13 16:04:05 -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/.