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    SubjectRe: [PATCH 08/12] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu()
    On Wed, Mar 04, 2020 at 04:12:40PM +0000, Alex Belits wrote:
    > From: Yuri Norov <ynorov@marvell.com>
    >
    > For nohz_full CPUs the desirable behavior is to receive interrupts
    > generated by tick_nohz_full_kick_cpu(). But for hard isolation it's
    > obviously not desirable because it breaks isolation.
    >
    > This patch adds check for it.
    >
    > Signed-off-by: Alex Belits <abelits@marvell.com>
    > ---
    > kernel/time/tick-sched.c | 3 ++-
    > 1 file changed, 2 insertions(+), 1 deletion(-)
    >
    > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
    > index 1d4dec9d3ee7..fe4503ba1316 100644
    > --- a/kernel/time/tick-sched.c
    > +++ b/kernel/time/tick-sched.c
    > @@ -20,6 +20,7 @@
    > #include <linux/sched/clock.h>
    > #include <linux/sched/stat.h>
    > #include <linux/sched/nohz.h>
    > +#include <linux/isolation.h>
    > #include <linux/module.h>
    > #include <linux/irq_work.h>
    > #include <linux/posix-timers.h>
    > @@ -262,7 +263,7 @@ static void tick_nohz_full_kick(void)
    > */
    > void tick_nohz_full_kick_cpu(int cpu)
    > {
    > - if (!tick_nohz_full_cpu(cpu))
    > + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu))
    > return;

    I fear you can't do that. A nohz full CPU is kicked for a reason.
    As for the other cases, you need to fix the callers.

    In the general case, randomly ignoring an interrupt is a correctness
    issue.

    Thanks.

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