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* faq-using.xml (faq.using.fixing-fork-failures): Add new FAQ.

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* overview2.sgml (ov-hi-process-problems): Describe some difficulties
	in implementing fork()
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Jon TURNEY
2011-11-05 18:42:55 +00:00
parent 481b6ac0c8
commit cd561fdb8b
3 changed files with 94 additions and 1 deletions
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winsup/doc/faq-using.xml
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@@ -1099,7 +1099,7 @@ it.</para>
IPv6 stack, see the <ulink url="http://www.microsoft.com/technet/network/ipv6/ipv6faq.mspx">Microsoft TechNet IPv6 FAQ article</ulink>
</para></answer></qandaentry>
<qandaentry id="faq.using.bloda">
<qandaentry id="faq.using.bloda" xreflabel="BLODA">
<question><para>What applications have been found to interfere with Cygwin?</para></question>
<answer>
@@ -1199,3 +1199,39 @@ such as virtual memory paging and file caching.</para>
</listitem>
</itemizedlist></para>
</answer></qandaentry>
<qandaentry id='faq.using.fixing-fork-failures'>
<question><para>How do I fix <literal>fork()</literal> failures?</para></question>
<answer>
<para>Unfortunately, Windows does not use the fork/exec model of process creation
found in UNIX-like OSes, so it is difficult for Cygwin to implement a reliable and
correct <literal>fork()</literal>, which can lead to error messages such as:</para>
<para><itemizedlist>
<listitem>unable to remap <emphasis>somedll</emphasis> to same address as parent</listitem>
<listitem>couldn't allocate heap</listitem>
<listitem>died waiting for dll loading</listitem>
<listitem>child -1 - died waiting for longjmp before initialization</listitem>
<listitem>STATUS_ACCESS_VIOLATION</listitem>
<listitem>resource temporarily unavailable</listitem>
</itemizedlist></para>
<para>Potential solutions for the above errors:</para>
<para><itemizedlist>
<listitem>Restart whatever process is trying (and failing) to use
<literal>fork()</literal>. Sometimes Windows sets up a process
environment that is even more hostile to fork() than usual.</listitem>
<listitem>Ensure that you have eliminated (not just disabled) all
software on the <xref linkend="faq.using.bloda"/>.
</listitem>
<listitem>Read the 'rebase' package README in
<literal>/usr/share/doc/rebase/</literal>, and follow the
instructions there to run 'rebaseall'.</listitem>
</itemizedlist></para>
<para>Please note that installing new packages or updating existing
ones undoes the effects of rebaseall and often causes fork() failures
to reappear. If so, just run rebaseall again.
</para>
<para>See the <ulink url="http://cygwin.com/cygwin-ug-net/highlights.html#ov-hi-process">
process creation</ulink> section of the User's Guide for the technical reasons it is so
difficult to make <literal>fork()</literal> work reliably.</para>
</answer>
</qandaentry>