Re: RFC: import of posix_spawn GSoC results

[Martin Husemann <martin%duskware.de@localhost>]

On Wed, Dec 28, 2011 at 04:07:45AM +0000, YAMAMOTO Takashi wrote:
> my understanding:
> there is no need to stop other threads as far as posix_spawn is concerned.
> so there is no big performace problems with a vfork-based implementation.
> because our current implementation of vfork suspends the calling threads
> only, it can be used to implement posix_spawn as it is.  a vfork'ed child
> should carefully avoid touching memory shared with other threads, but it's
> doable and not too complex.

I'm confused - exactly due to the above, I don't see how it is possible
to use vfork() in a multithreaded application safely. Don't other parent
threads touching arbitrary memory violate the basic vfork assumption of a
fixed shared VM state untill child does the exec?

If not, I don't see the need for posix_spawn() at all (besides interface
simplicity, but a libarary wrapper would do, as you say).

Martin