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    Subject[RFC PATCH 13/15] sched: Protect nohz task cpu affinity
    Date
    Don't allow to change a nohz task cpu affinity as we want them
    to be bound to a single CPU and we want this affinity not to
    change.

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Anton Blanchard <anton@au1.ibm.com>
    Cc: Tim Pepper <lnxninja@linux.vnet.ibm.com>
    ---
    kernel/sched.c | 7 +++++++
    1 files changed, 7 insertions(+), 0 deletions(-)

    diff --git a/kernel/sched.c b/kernel/sched.c
    index 4412493..bd0a41f 100644
    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -5712,6 +5712,13 @@ again:
    goto out;
    }

    + /* Nohz tasks must keep their affinity */
    + if (test_tsk_thread_flag(p, TIF_NOHZ) &&
    + !cpumask_equal(&p->cpus_allowed, new_mask)) {
    + ret = -EBUSY;
    + goto out;
    + }
    +
    if (p->sched_class->set_cpus_allowed)
    p->sched_class->set_cpus_allowed(p, new_mask);
    else {
    --
    1.7.3.2


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