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    Subject[PATCH AUTOSEL for 4.14 39/60] powerpc/watchdog: Do not trigger SMP crash from touch_nmi_watchdog
    Date
    From: Nicholas Piggin <npiggin@gmail.com>

    [ Upstream commit 80e4d70b06863e0104e5a0dc78aa3710297fbd4b ]

    In xmon, touch_nmi_watchdog() is not expected to be checking that
    other CPUs have not touched the watchdog, so the code will just call
    touch_nmi_watchdog() once before re-enabling hard interrupts.

    Just update our CPU's state, and ignore apparently stuck SMP threads.

    Arguably touch_nmi_watchdog should check for SMP lockups, and callers
    should be fixed, but that's not trivial for the input code of xmon.

    Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    ---
    arch/powerpc/kernel/watchdog.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
    index 57190f384f63..ce848ff84edd 100644
    --- a/arch/powerpc/kernel/watchdog.c
    +++ b/arch/powerpc/kernel/watchdog.c
    @@ -276,9 +276,12 @@ void arch_touch_nmi_watchdog(void)
    {
    unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
    int cpu = smp_processor_id();
    + u64 tb = get_tb();

    - if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
    - watchdog_timer_interrupt(cpu);
    + if (tb - per_cpu(wd_timer_tb, cpu) >= ticks) {
    + per_cpu(wd_timer_tb, cpu) = tb;
    + wd_smp_clear_cpu_pending(cpu, tb);
    + }
    }
    EXPORT_SYMBOL(arch_touch_nmi_watchdog);

    --
    2.11.0
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