Re: question about _exit() function

From: Terry Lambert (tlambert2_at_mindspring.com)
Date: 11/28/03

  • Next message: rmkml: "Re: question about _exit() function" 
    Date: Fri, 28 Nov 2003 04:46:31 -0800
To: rmkml <rmkml@wanadoo.fr>

    rmkml wrote:
    > is the _exit() function safe for a thread ?
    > my program use vfork() and then execve in a thread context.
    > The documentation mentions that the process has to call _exit() in case
    > of failure.
    > But this _exit() is really safe for the parent thread ?

    The behaviour is undefined in the failure case, but only if you
    have stablishd a pthread_atfork() handler that does anything in
    the child.

    In general, the more correct approach is to use posix_spawn(), but
    FreeBSD doesn't support posix_spawn() (funny; this has come up now
    twice in within 60 messages of each other, while ther was a very
    long time when it was not pertinent at all...).

    POSIX also sriously discourages the use of vfork(), and recommends
    fork() instead, for threaded programs.

    Note that the fork() only *ever* creates a single thread, so it
    will only replicate the currently running thread and its address
    space, rather than all currently running threads in the parent.

    You said in another message that this is on 4.8. I think that the
    behaviour will not be quite what you expect, in that case, and that
    it'll be better in -current, but might still not be what you expect
    there, either (depends on what you are expecting). See also:

    http://www.opengroup.org/onlinepubs/007904975/functions/fork.html

    -- Terry
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  • Next message: rmkml: "Re: question about _exit() function"

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