Re: [gtk-vnc-devel] [RFC] GThread based coroutines

[Anthony Liguori <anthony codemonkey ws>]

Daniel P. Berrange wrote:
> On Tue, Dec 18, 2007 at 10:51:05PM -0500, Anthony Liguori wrote:
>   
> > Hi,
> >
> > Attached a thread-based coroutine implementation.  This should make the 
> > Windows port much easier.  I've tested it with gvncviewer and vinagre 
> > (with multiple tabs) so I think it works pretty well.  The basic idea is 
> > to use a GCond and GMutex to run all threads in lock-step.  It was 
> > tricky getting the ucontext coroutines working properly so 
> > testing/review is greatly appreciated!
> >
> > Also, I'm hoping someone who has a bit more autoconf foo can help me 
> > with the proper autoconf/automake integration.  We need to detect 
> > ucontext in configure and if it's available, compile in 
> > ucontext_coroutine.[ch], continuation.[ch].  Otherwise, we need to add a 
> > dependency to gthread-2.0 and compile in gthread_coroutine.[ch].
> >     
>
> Here's an updated patch with autoconf magic. There wre a couple of things
> I needed to deal with:
>
> When we do 'make install' we also install the coroutine headers. This
> doesn't work so well because your patch has #ifdef in the coroutine.h
> to then #include either the gthread or ucontext header, and this #ifdef
> depends on a variable set from configure.ac
>
> I observed that the structs required for ucontext vs gthread were more or
> less the same except for the GThread * vs  struct continuation. So I unified
> them into a generic 'void *context'. In the implementation this context 
> points to a GThread * or a 'struct continuation *' as needed. The latter
> means the 'container_of' trick doesn't work, so I simply added 'void *owner'
> to the 'struct continuation'.
>
> The GThread patch doesn't go correct (well any) GThread cleanup when the
> coroutine exits - we need to join & also free the GThread * object. I
> didn't try to address this.
>   

Actually, when a coroutine exits, the thread resources should be freed 
since the threads are created as non-joinable.  I looked over the glib 
manual again and that seems to be the behavior.

Regards,

Anthony Liguori

> configure now has '--with-coroutine=ucontext|gthread', defaulting to 
> 'ucontext' and automatically switching to 'gthread' if it can't find
> the getcontext/makecontext/swapcontext function calls.
>
>  a/src/coroutine.c          |  121 ----------------------------------------
>  b/src/coroutine_gthread.c  |  129 +++++++++++++++++++++++++++++++++++++++++++
>  b/src/coroutine_ucontext.c |  133 +++++++++++++++++++++++++++++++++++++++++++++
>  configure.ac               |   35 +++++++++++
>  src/Makefile.am            |   20 +++++-
>  src/continuation.h         |    1 
>  src/coroutine.h            |    8 +-
>  7 files changed, 317 insertions(+), 130 deletions(-)
>
>
> Regards,
> Dan.
>