Re: [Xen-devel] [PATCH 1/2] xen: export do_yield as vcpu_yield

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 23 Jul 2014, George Dunlap wrote:
> On 07/23/2014 01:05 PM, Stefano Stabellini wrote:
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > CC: george.dunlap@xxxxxxxxxxxxx
> > CC: JBeulich@xxxxxxxx
> > ---
> >   xen/common/schedule.c   |   10 +++++-----
> >   xen/include/xen/sched.h |    1 +
> >   2 files changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/xen/common/schedule.c b/xen/common/schedule.c
> > index e9eb0bc..6631dc8 100644
> > --- a/xen/common/schedule.c
> > +++ b/xen/common/schedule.c
> > @@ -795,9 +795,8 @@ static long do_poll(struct sched_poll *sched_poll)
> >   }
> >     /* Voluntarily yield the processor for this allocation. */
> > -static long do_yield(void)
> > +void vcpu_yield(struct vcpu *v)
> 
> What are you actually trying to do here?  Why do you add a vcpu struct, when
> all the callers (including the one you add in 2/2) just pass current?

I was just trying to be coherent with the other vcpu_* functions in
sched.h.


> >   {
> > -    struct vcpu * v=current;
> >       spinlock_t *lock = vcpu_schedule_lock_irq(v);
> >         SCHED_OP(VCPU2OP(v), yield, v);
> > @@ -805,7 +804,6 @@ static long do_yield(void)
> >         TRACE_2D(TRC_SCHED_YIELD, current->domain->domain_id,
> > current->vcpu_id);
> >       raise_softirq(SCHEDULE_SOFTIRQ);
> 
> This is broken: it's still tracing current instead of v, and you're raising
> the schedule softirq on the current cpu rather than on the cpu on which v is
> running.  If v!=current, you have to go through force reschedule for safety.
> 
> Just rename the function and make it non-static, leaving the arguments and
> return value alone.

OK

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