[Bug 199557] Hang on sysconf(_SC_OPEN_MAX)

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=199557

Jilles Tjoelker <jilles at FreeBSD.org> changed:

           What    |Removed                     |Added
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                 CC|                            |jilles at FreeBSD.org

--- Comment #7 from Jilles Tjoelker <jilles at FreeBSD.org> ---
There is a proposal for an async-signal safe version of fork() called _Fork(),
which does not call atfork handlers, at
http://austingroupbugs.net/view.php?id=62 . This would help if the only problem
with calling fork() is that it executes atfork handlers. It still executes a
fair bit of code, but no user code.

To make _Fork() async-signal safe, the malloc handling would have to be
disabled as well, making malloc/free in the child more unsafe (but also
interfering less with other threads in the parent). The handling of the lock
for sem_open() and sem_close() uses pthread_atfork() and would be disabled as
well.

This may be useful for this and other situations that want to fork from signal
handlers or other strange thread states.

I have not found common implementations of _Fork(), though.

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