Re: [patch 02/38] CKRM e18: Processor Delay Accounting

[Ingo Molnar <mingo@elte.hu>]

* Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Gerrit Huizenga <gh@us.ibm.com> wrote:
> 
> > +#ifdef CONFIG_DELAY_ACCT
> > +int task_running_sys(struct task_struct *p)
> > +{
> > +	return task_is_running(p);
> > +}
> > +EXPORT_SYMBOL_GPL(task_running_sys);
> > +#endif
> 
> why is this function defined, and why is it exported?

this:

+#define task_is_running(p)     (this_rq() == task_rq(p))

is totally bogus. What you are checking is not whether 'the task is 
running', but it is a complex way of doing p->thread_info->cpu == 
smp_processor_id(). This, combined with:

+               if (pdata == NULL)
+                       /* some wierdo race condition .. simply ignore */
+                       continue;
+               if (thread->state == TASK_RUNNING) {
+                       if (task_running_sys(thread)) {
+                               atomic_inc((atomic_t *) &
+                                          (PSAMPLE(pdata)->cpu_running));
+                               run++;
+                       } else {
+                               atomic_inc((atomic_t *) &
+                                          (PSAMPLE(pdata)->cpu_waiting));
+                               wait++;
+                       }
+               }

yields completely incorrect code, and bogus data. If your goal is to 
sample executing-on-cpu vs. on-runqueue-waiting-to-run states then you 
should use the already existing task_curr(p) call.

	Ingo