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    SubjectRe: [PATCH 19/32] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset
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    On Mon, 2011-08-15 at 17:52 +0200, Frederic Weisbecker wrote:
    > +++ b/kernel/cpuset.c
    > @@ -1199,6 +1199,14 @@ static void cpuset_change_flag(struct task_struct *tsk,
    >
    > DEFINE_PER_CPU(int, cpu_adaptive_nohz_ref);
    >
    > +static void cpu_exit_nohz(int cpu)
    > +{
    > + preempt_disable();
    > + smp_call_function_single(cpu, cpuset_exit_nohz_interrupt,
    > + NULL, true);
    > + preempt_enable();
    > +}
    > +
    > static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs)
    > {
    > int cpu;
    > @@ -1212,6 +1220,19 @@ static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs)
    > per_cpu(cpu_adaptive_nohz_ref, cpu) += 1;
    > else
    > per_cpu(cpu_adaptive_nohz_ref, cpu) -= 1;
    > +
    > + val = per_cpu(cpu_adaptive_nohz_ref, cpu);
    > +
    > + if (!val) {
    > + /*
    > + * The update to cpu_adaptive_nohz_ref must be
    > + * visible right away. So that once we restart the tick
    > + * from the IPI, it won't be stopped again due to cache
    > + * update lag.
    > + */
    > + smp_mb();
    > + cpu_exit_nohz(cpu);
    > + }
    > }
    > }
    > #else
    > diff --git a/kernel/sched.c b/kernel/sched.c
    > index 78ea0a5..75378be 100644
    > --- a/kernel/sched.c
    > +++ b/kernel/sched.c
    > @@ -2513,6 +2513,14 @@ void cpuset_update_nohz(void)
    > cpuset_nohz_restart_tick();
    > }
    >
    > +void cpuset_exit_nohz_interrupt(void *unused)
    > +{
    > + if (!tick_nohz_adaptive_mode())
    > + return;
    > +
    > + cpuset_nohz_restart_tick();
    > +}

    You do this just to annoy me, right? Why doesn't it live in cpuset.c
    where you use it?


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