Fibers and TLS woes

[Kai Nacke via digitalmars-d-ldc]

On Saturday, 28 February 2015 at 18:10:13 UTC, Dan Olson wrote:
> I discovered why one of the Fiber unittests in core.thread 
> would crash
> on iOS. TLS address is looked up based on the thread. In LDC 
> optimized
> code, the address lookup may only happen once in a function if 
> the
> address can be cached in a register. This is good, because it 
> makes
> multiple TLS access faster in a single function.
>
> Now, Fibers are permitted to be run on different threads, as 
> long as
> only one thread has it active at a time. The problem is that 
> the Fiber
> context may be on a different thread before and after a 
> yeild(). If a
> TLS address is cached, the previous thread's TLS is accessed 
> after the
> yield call instead of the current threads TLS.
>
> To make the one Fiber unittest work on multicore, I am switch 
> to using
> pthread_getspecific intead of TLS for sm_this. But in general 
> this is a
> problem with other architectures besides arm. I checked 
> assembly of
> x86_64 and TLS addresses are cached too when optimization is on.
>
> I also looked at DMD asm, and it does not seem to cache TLS 
> addresses on
> OS X at least.
> --
> Dan

Hi Dan,

this is issue 666: 
https://github.com/ldc-developers/ldc/issues/666

Regards,
Kai