Re: [Qemu-devel] [PATCH 2/3] coroutine: Clean up qemu_coroutine_enter()

[Stefan Hajnoczi]

On Wed, Feb 18, 2015 at 03:20:26PM +0100, Kevin Wolf wrote:
> Am 18.02.2015 um 14:50 hat Stefan Hajnoczi geschrieben:
> > On Tue, Feb 10, 2015 at 11:41:27AM +0100, Kevin Wolf wrote:
> > > qemu_coroutine_enter() is now the only user of coroutine_swap(). Both
> > > functions are short, so inline it.
> > > 
> > > Also, using COROUTINE_YIELD is now even more confusing because this code
> > > is never called during qemu_coroutine_yield() any more. In fact, this
> > > value is never read back, so we can just introduce a new COROUTINE_ENTER
> > > which documents the purpose of the task switch better.
> > > 
> > > Signed-off-by: Kevin Wolf <address@hidden>
> > > ---
> > >  include/block/coroutine_int.h |  1 +
> > >  qemu-coroutine.c              | 36 +++++++++++++++---------------------
> > >  2 files changed, 16 insertions(+), 21 deletions(-)
> > > 
> > > diff --git a/include/block/coroutine_int.h b/include/block/coroutine_int.h
> > > index f133d65..69b83db 100644
> > > --- a/include/block/coroutine_int.h
> > > +++ b/include/block/coroutine_int.h
> > > @@ -29,6 +29,7 @@
> > >  #include "block/coroutine.h"
> > >  
> > >  typedef enum {
> > > +    COROUTINE_ENTER = 0,
> > 
> > This makes the ucontext code harder to understand because
> > CoroutineAction values are used with setjmp()/longjmp() in
> > qemu_coroutine_switch().
> > 
> > The longjmp() man page says:
> > 
> >   If longjmp() is invoked with a second argument of 0, 1 will be
> >   returned instead.
> > 
> > I haven't checked whether or not this causes problems, but the code
> > would be simpler if we avoided using 0.
> 
> It doesn't, the value is unused where we pass COROUTINE_ENTER. But I can
> make it 3 instead.

Thanks, that would be good.

Stefan

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