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Re: GNUnet News: vfork and the signal race


From: Thomas Bushnell, BSG
Subject: Re: GNUnet News: vfork and the signal race
Date: Fri, 25 Nov 2011 10:50:05 -0800

Programs which depend on the special suspend-the-parent behavior of vfork were always regarded as buggy...

Thomas

On Fri, Nov 25, 2011 at 7:42 AM, Thomas Schwinge <thomas@schwinge.name> wrote:
Hallo!

On Thu, 24 Nov 2011 15:59:55 -0000, Planet GNU <tschwinge+news@gnu.org> wrote:
> Many articles uniformly claim that using vfork should be
> [avoided][1] and that the only difference between vfork and fork is (or
> used-to-be) [performance][2] and that thus vfork is [obsolte][3]. Here, I
> wanted to document a technical case where vfork is actually required and
> where using vfork instead of fork (or operating system implementors
> implementing vfork as an alias for fork) causes a hard-to-find data race.
> [...]
> URL: https://gnunet.org/vfork

Rather ``using *fork* instead of *vfork*'', I assume?


Just for the record, the Hurd doesn't have a vfork implementation, and
we're thus using glibc's default POSIX vfork implementation:

   /* If we don't have vfork, fork is close enough.  */

   __pid_t
   __vfork (void)
   {
     return __fork ();
   }

I wonder how clumsy it would get to add vfork's ``parent blocks until the
child calls _exit or exec'' functionality.


Grüße,
 Thomas


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