Re: [Boost-users] [boost] Boost.Fiber mini-review September 4-13

Subject: Re: [Boost-users] [boost] Boost.Fiber mini-review September 4-13
From: Oliver Kowalke (oliver.kowalke_at_[hidden])
Date: 2015-09-05 15:35:58

2015-09-05 21:31 GMT+02:00 Hartmut Kaiser <hartmut.kaiser_at_[hidden]>:

>
> > what does that mean 'maintained by the runtime'?
> > void bar( ptr_scheduler_thread_local_var) {
> >   printf("%p\n", ptr_scheduler_thread_local_var);
> >   suspend_and_migrate_fiber();
> > }
> >
> > void foo() {
> >    while ( true) {
> >       bar( return_ptr_of_scheduler_thread_local_var() );
> >       ...
> >    }
> > }
> > in this example b) accesses a) (TLS of scheduler) prints in to stdout
> > suspends active fiber and migrates it to another thread
> > after resumption the address of the TLS-scheduler is printed out ...
> > how does your code look like after compiler optimization?!
>
> a) is safe as all threads sharing the same scheduler store the same
> reference (fibers can be moved only inside that scheduler)
> b) is safe as the runtime sets the reference to the fiber it is about to
> run in TLS and resets it right after the fiber returned.
>

but I was asking for the code snipped which accesses TLS variable - if all
threads share the same scheduler why has it to be stored in TLS?
a slight modification of my example above - replace
retrn_ptr_of_scheduler_thread_lcoal_var() by return_ptr_to_active_fiber()
I assume that as you mentioned in b) that the active fiber is stored in TLS
- the exmaple code prints out the address of the current active fiber

how does the code look like after compiler optimization?