• Vincent Guittot's avatar
    sched/rt: Fix call to cpufreq_update_util() · 296b2ffe
    Vincent Guittot authored
    With commit:
    
      8f111bc3 ("cpufreq/schedutil: Rewrite CPUFREQ_RT support")
    
    the schedutil governor uses rq->rt.rt_nr_running to detect whether an
    RT task is currently running on the CPU and to set frequency to max
    if necessary.
    
    cpufreq_update_util() is called in enqueue/dequeue_top_rt_rq() but
    rq->rt.rt_nr_running has not been updated yet when dequeue_top_rt_rq() is
    called so schedutil still considers that an RT task is running when the
    last task is dequeued. The update of rq->rt.rt_nr_running happens later
    in dequeue_rt_stack().
    
    In fact, we can take advantage of the sequence that the dequeue then
    re-enqueue rt entities when a rt task is enqueued or dequeued;
    As a result enqueue_top_rt_rq() is always called when a task is
    enqueued or dequeued and also when groups are throttled or unthrottled.
    The only place that not use enqueue_top_rt_rq() is when root rt_rq is
    throttled.
    Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: efault@gmx.de
    Cc: juri.lelli@redhat.com
    Cc: patrick.bellasi@arm.com
    Cc: viresh.kumar@linaro.org
    Fixes: 8f111bc3 ('cpufreq/schedutil: Rewrite CPUFREQ_RT support')
    Link: http://lkml.kernel.org/r/1530021202-21695-1-git-send-email-vincent.guittot@linaro.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    296b2ffe
rt.c 63 KB