On Thu, Sep 29, 2011 at 04:35:04PM +0100, Alaric Snell-Pym wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 09/29/2011 04:25 PM, Jörg F. Wittenberger wrote: > > >> POSIX says that fork needs to produce only a single surviving POSIX > >> thread in the child. Perhaps Chicken fork needs to do the same with > >> Chicken threads. > > > > Alaric, that's exactly the effect and reason why I'm using this > > disable-interrupts/enable-interrupts around fork: to make sure > > there is only this one Chicken-threads running in the child. > > With interrupts disabled there is no scheduling in chicken. > > (At least not until you run into a thread-yield! anyway.) > > > > And therefore I'd really recommend to keep it in the runtime. > > I think a better mechanism would be a way to abort all threads but the > current one, triggered after the fork in the child, with no interrupts > until the thread murder is complete. > > If you just go off and exec after the fork it'd be better to > uninterruptably vfork-then-exec, but we have procedures to do that already! > > Aborting all threads but the one that asked for the fork also gives one > the opportunity to inform them of this fact, should any of them leave > useful data structures in incosistent states with locks held. There's > something to be said for requesting permission to fork from all threads > before doing so, so they can make sure they finish any operations on > shared state in the parent, but that'll be complex, and a potential > performance bottleneck, so probably not worth it! > > ABS >
In posix threads, this is what pthread_atfork() is for--to clean up resources in the process of joining threads across a fork. The way Chicken is currently implemented, any signal that arrives during this time is discarded, which also makes me unhappy with this situation. A lot of blood and tears were spilled over signal handling on Unix to get to reliable signal delivery. I don't think Chicken should implement unreliable signal delivery on top of a reliable mechanism. It seems that the thread-like nature of signal handling and the thread-like nature of threading have been intermixed in the scheduler, and this particular feature is at cross-purposes. -Alan -- .i ma'a lo bradi cu penmi gi'e du _______________________________________________ Chicken-users mailing list Chicken-users@nongnu.org https://lists.nongnu.org/mailman/listinfo/chicken-users
