[Bug nptl/14499] New: Does posix_spawn invoke atfork handlers / use vfork?

["luto at mit dot edu" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14499

             Bug #: 14499
           Summary: Does posix_spawn invoke atfork handlers / use vfork?
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
        AssignedTo: unassigned@sourceware.org
        ReportedBy: luto@mit.edu
                CC: drepper.fsp@gmail.com
    Classification: Unclassified


The resolution of bug 378 indicates that glibc's (NPTL) posix_spawn calls
atfork handlers.  This means that posix_spawn can't use vfork (or fancy clone
options), which makes it slow.  (Note that, AFAICT, this behavior is not
documented anywhere, despite being implementation-specified.)

This was apparently true when bug 378 was closed, but it changed in commit
a9f43ef464f71b0d379524b2a6294092332c9a30.  The current behavior is bizarre. 
See the attached code, which invokes atfork handlers only on the second
posix_spawn call.

IMO the right fix is to never invoke atfork handlers (since presumably nothing
relies on them getting called, since they haven't been reliably called since
2005).  That way vfork can be used unconditionally, which is faster.

See also bug 10354, which does not have a resolution that I understand.

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