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SubjectRe: [PATCH 08/14] sched: add latency tracing for -deadline tasks.
On Thu,  7 Nov 2013 14:43:42 +0100
Juri Lelli <juri.lelli@gmail.com> wrote:


> + /*
> + * Semantic is like this:
> + * - wakeup tracer handles all tasks in the system, independently
> + * from their scheduling class;
> + * - wakeup_rt tracer handles tasks belonging to sched_dl and
> + * sched_rt class;
> + * - wakeup_dl handles tasks belonging to sched_dl class only.
> + */
> + if ((wakeup_dl && !dl_task(p)) ||
> + (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
> + (p->prio >= wakeup_prio || p->prio >= current->prio))
> return;
>
> pc = preempt_count();
> @@ -486,7 +495,7 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
> arch_spin_lock(&wakeup_lock);
>
> /* check for races. */
> - if (!tracer_enabled || p->prio >= wakeup_prio)
> + if (!tracer_enabled || (!dl_task(p) && p->prio >= wakeup_prio))
> goto out_locked;

We probably want to add a "tracing_dl" variable, and do the test like
this:

if (!tracer_enabled || tracing_dl ||
(!dl_task(p) && p->prio >= wakeup_prio))

and for the first if statement too. Otherwise if two dl tasks are
running on two different CPUs, the second will override the first. Once
you start tracing a dl_task, you shouldn't bother tracing another task
until that one wakes up.

if (dl_task(p))
tracing_dl = 1;
else
tracing_dl = 0;

-- Steve


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