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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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