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    Subject[PATCH 4.14 63/64] tick/nohz: Prevent bogus softirq pending warning
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Thomas Gleixner <tglx@linutronix.de>

    Commit 0a0e0829f990 ("nohz: Fix missing tick reprogram when interrupting an
    inline softirq") got backported to stable trees and now causes the NOHZ
    softirq pending warning to trigger. It's not an upstream issue as the NOHZ
    update logic has been changed there.

    The problem is when a softirq disabled section gets interrupted and on
    return from interrupt the tick/nohz state is evaluated, which then can
    observe pending soft interrupts. These soft interrupts are legitimately
    pending because they cannot be processed as long as soft interrupts are
    disabled and the interrupted code will correctly process them when soft
    interrupts are reenabled.

    Add a check for softirqs disabled to the pending check to prevent the
    warning.

    Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
    Reported-by: John Crispin <john@phrozen.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
    Tested-by: John Crispin <john@phrozen.org>
    Cc: Frederic Weisbecker <frederic@kernel.org>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
    Cc: stable@vger.kernel.org
    Fixes: 2d898915ccf4838c ("nohz: Fix missing tick reprogram when interrupting an inline softirq")
    Acked-by: Frederic Weisbecker <frederic@kernel.org>
    Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
    ---
    kernel/time/tick-sched.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/time/tick-sched.c
    +++ b/kernel/time/tick-sched.c
    @@ -908,7 +908,7 @@ static bool can_stop_idle_tick(int cpu,
    if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
    static int ratelimit;

    - if (ratelimit < 10 &&
    + if (ratelimit < 10 && !in_softirq() &&
    (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
    pr_warn("NOHZ: local_softirq_pending %02x\n",
    (unsigned int) local_softirq_pending());

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