Re: sched_clock - microblaze

Michal Simek
2010-04-16T06:23:16Z

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