Re: sched_clock - microblaze

[Michal Simek]

Arnd Bergmann wrote:
> On Thursday 15 April 2010 21:29:27 Michal Simek wrote:
> > > sched_clock() {
> > >       ftrace_stop();
> > >       printk(...);
> > >       ftrace_start();
> > >       ...
> > > }
> > But I am describing different problem. sched_clock is called before 
> > kernel initialized timers. Microblaze takes all information from DTS 
> > that's means that I am not able to read timer because I even don't know 
> > where it is. :-(
>
> You could make sched_clock return zero before the clock is probed, it
> is very unlikely to be needed before that anyway.

First of all - this technique works.

That calling sequence is
main.c: sched_init() -> sched.c: sched_init(); -> init_idle(); -> 
sched_clock() without initialized timer which is causing my problems.

Why is sched_clock called in init_idle? Do you get any non zero value on 
any ARCH?

Thanks,
Michal

diff --git a/kernel/sched.c b/kernel/sched.c
index 6af210a..bddd918 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5244,7 +5244,7 @@ void __cpuinit init_idle(struct task_struct *idle, 
int cpu)

        __sched_fork(idle);
        idle->state = TASK_RUNNING;
-       idle->se.exec_start = sched_clock();
+       idle->se.exec_start = 0;

        cpumask_copy(&idle->cpus_allowed, cpumask_of(cpu));
        __set_task_cpu(idle, cpu);

--
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663
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