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See #26688: getenv() is not thread-safe, and could a possible source of problems when a multi-threaded program calls setenv()/putenv()/unsetenv() in parallel. It is not possible to avoid getenv() calls in general, since $PATH, $LANG, $SHELL, $USER, $HOME, $TZ may need to be accessed at any time. Add a warning to our docs so that people are aware of the issue. Closes #26688. (Real fixes will need to be in glibc and gnome-shell or other programs.) The text is added to threads-aware.xml to be included in various places. By including it in libsystemd-pkgconfig.xml, it is automatically added to all sd-* pages. The text is also included explicitly in pages for a few other functions which are call getenv().
24 lines
1.3 KiB
XML
24 lines
1.3 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refsect1>
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<para id="strict">All functions listed here are thread-agnostic and only a single specific thread may operate on a
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given object during its entire lifetime. It's safe to allocate multiple independent objects and use each from a
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specific thread in parallel. However, it's not safe to allocate such an object in one thread, and operate or free it
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from any other, even if locking is used to ensure these threads don't operate on it at the very same time.</para>
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<para id="safe">All functions listed here are thread-safe and may be called in parallel from multiple threads.</para>
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<para id='getenv'>The code described here uses
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<citerefentry project='man-pages'><refentrytitle>getenv</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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which is declared to be not multi-thread-safe. This means that the code calling the functions described
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here must not call
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<citerefentry project='man-pages'><refentrytitle>setenv</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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from a parallel thread. It is recommended to only do calls to <function>setenv()</function>
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from an early phase of the program when no other threads have been started.</para>
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</refsect1>
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