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Allow libpq to do thread-safe SIGPIPE handling. This allows it to

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ignore SIGPIPE from send() in libpq, but terminate on any other SIGPIPE,
unless the user installs their own signal handler.

This is a minor fix because the only time you get SIGPIPE from libpq's
send() is when the backend dies.
This commit is contained in:
Bruce Momjian
2004-01-09 02:02:43 +00:00
parent acc57543de
commit 0150dbdce5
9 changed files with 167 additions and 12 deletions
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23
doc/src/sgml/libpq.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.144 2003/12/13 23:59:06 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.145 2004/01/09 02:02:43 momjian Exp $
-->
<chapter id="libpq">
@ -3587,7 +3587,7 @@ thread-enabled applications.
One restriction is that no two threads attempt to manipulate the same
<structname>PGconn</> object at the same time. In particular, you cannot
issue concurrent commands from different threads through the same
connection object. (If you need to run concurrent commands, start up
connection object. (If you need to run concurrent commands, use
multiple connections.)
</para>
@ -3612,6 +3612,25 @@ not thread-safe.<indexterm><primary>crypt</><secondary>thread
safety</></> It is better to use the <literal>md5</literal> method,
which is thread-safe on all platforms.
</para>
<para>
<application>libpq</application> must ignore <literal>SIGPIPE</> signals
generated internally by <function>send()</> calls to backend processes.
When <productname>PostgreSQL</> is configured without
<literal>--enable-thread-safety</>, <application>libpq</> sets
<literal>SIGPIPE</> to <literal>SIG_IGN</> before each
<function>send()</> call and restores the original signal handler after
completion. When <literal>--enable-thread-safety</> is used,
<application>libpq</> installs its own <literal>SIGPIPE</> handler
before the first database connection if no custom <literal>SIGPIPE</>
handler has been installed previously. This handler uses thread-local
storage to determine if a <literal>SIGPIPE</> signal has been generated
by an internal <function>send()</>. If an application wants to install
its own <literal>SIGPIPE</> signal handler, it should call
<function>PQinSend()</> to determine if it should ignore the
<literal>SIGPIPE</> signal. This function is available in both
thread-safe and non-thread-safe versions of <application>libpq</>.
</para>
</sect1>