Re: Go patch committed: Multiplex goroutines onto OS threads

[Paolo Bonzini <bonzini at gnu dot org>]

On 11/28/2011 06:46 AM, Ian Lance Taylor wrote:
> This implementation relies on the functions getcontext, setcontext, and
> makecontext.  If there are systems which don't have those, getcontext
> and setcontext can be replaced by setjmp and longjmp, but there is no
> obvious replacement for makecontext.  I think that will have to be
> implemented using processor-specific code, as it needs to set the stack
> pointer to point to a new stack, and I don't know how to do that in a
> portable processor-independent manner without using makecontext.

ARM glibc does not implement these functions, so we have the same 
problem in QEMU.  (On top of this, there is no way that alternate stacks 
can work on OpenBSD, so we still have one coroutine per thread).

For QEMU, I tried replacing for makecontext using sigaltstack.  It works 
on Linux but it needs a dedicated signal, so it is likely inappropriate 
for libgo.  It would also need to be tested across many operating 
systems because it may trigger subtleties in other OSes.

Paolo