Re: linux-next: manual merge of the tip tree with the sparc tree

[Daniel Hellstrom]

Peter Zijlstra wrote:

> On Fri, 2011-05-20 at 08:07 +0200, Daniel Hellstrom wrote:
>  
>
> > Peter Zijlstra wrote:
> >
> >    
> >
> > > On Thu, 2011-05-19 at 15:37 +0200, Daniel Hellstrom wrote:
> > >
> > >
> > >
> > >
> > >      
> > >
> > > > diff --git a/arch/sparc/kernel/smp_32.c b/arch/sparc/kernel/smp_32.c
> > > > index 41102c5..d5b3958 100644
> > > > --- a/arch/sparc/kernel/smp_32.c
> > > > +++ b/arch/sparc/kernel/smp_32.c
> > > > @@ -156,11 +156,11 @@ void arch_send_call_function_ipi_mask(const struct 
> > > > cpumask *mask)
> > > >
> > > > void smp_resched_interrupt(void)
> > > > {
> > > > +       irq_enter();
> > > > +       scheduler_ipi();
> > > >       local_cpu_data().irq_resched_count++;
> > > > -       /*
> > > > -        * do nothing, since it all was about calling re-schedule
> > > > -        * routine called by interrupt return code.
> > > > -        */
> > > > +       irq_exit();
> > > > +       /* re-schedule routine called by interrupt return code. */
> > > > }
> > > >   
> > > >
> > > >        
> > > That doesn't look like an IPI, that looks like its calls the function on
> > > the local cpu, which is completely pointless.
> > >
> > >
> > >      
> > The above function is one of the IPI interrupt handlers.
> >
> > The smp_send_reschedule() is called by the generic code, it is 
> > responsible for sending an IRQ to the target CPU, that CPU comes into 
> > smp_resched_interrupt above from the IRQ trap handler. So yes, the 
> > scheduler_ipi() is called on the local CPU, but on the CPU taking the 
> > IPI not the CPU sending the IPI.
> >    
>
> Ah, clearly I cannot read well, I actually thought that was
> smp_send_reschedule(). OK, if sparc32 is now actually sending IPIs and
> the above is the handler, then you're completely right, sorry for the
> confusion.
>  
Yes, my patches implements IPI for sparc32.

> Also, since sparc32 now grew this IPI, you can remove:
>
> +++ b/init/Kconfig
> @@ -827,6 +827,11 @@ config SCHED_AUTOGROUP
>          desktop applications.  Task group autogeneration is currently based
>          upon task session.
>
> +config SCHED_TTWU_QUEUE
> +       bool
> +       depends on !SPARC32
> +       default y
> +
>  

Do you think this is an acceptable patch? If so I will send these two 
patches to the sparclinux list unless you think otherwise.

Thank you for enlightening this,
Daniel


Subject: [PATCH] SCHED_TTWU_QUEUE is not longer needed since sparc32 now 
implements IPI

Signed-off-by: Daniel Hellstrom <daniel@xxxxxxxxxxx>
Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
init/Kconfig   |    5 -----
kernel/sched.c |    2 +-
2 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index df64627..a66b656 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -827,11 +827,6 @@ config SCHED_AUTOGROUP
         desktop applications.  Task group autogeneration is currently 
based
         upon task session.

-config SCHED_TTWU_QUEUE
-       bool
-       depends on !SPARC32
-       default y
-
config MM_OWNER
       bool

diff --git a/kernel/sched.c b/kernel/sched.c
index c62acf4..0516af4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2564,7 +2564,7 @@ static void ttwu_queue(struct task_struct *p, int cpu)
{
       struct rq *rq = cpu_rq(cpu);

-#if defined(CONFIG_SMP) && defined(CONFIG_SCHED_TTWU_QUEUE)
+#if defined(CONFIG_SMP)
       if (sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) {
               ttwu_queue_remote(p, cpu);
               return;
--




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