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    Subject[PATCH 5.10 131/135] alpha: Send stop IPI to send to online CPUs
    Date
    From: Prarit Bhargava <prarit@redhat.com>

    [ Upstream commit caace6ca4e06f09413fb8f8a63319594cfb7d47d ]

    This issue was noticed while debugging a shutdown issue where some
    secondary CPUs are not being shutdown correctly. A fix for that [1] requires
    that secondary cpus be offlined using the cpu_online_mask so that the
    stop operation is a no-op if CPU HOTPLUG is disabled. I, like the author in
    [1] looked at the architectures and found that alpha is one of two
    architectures that executes smp_send_stop() on all possible CPUs.

    On alpha, smp_send_stop() sends an IPI to all possible CPUs but only needs
    to send them to online CPUs.

    Send the stop IPI to only the online CPUs.

    [1] https://lkml.org/lkml/2020/1/10/250

    Signed-off-by: Prarit Bhargava <prarit@redhat.com>
    Cc: Richard Henderson <rth@twiddle.net>
    Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    Signed-off-by: Matt Turner <mattst88@gmail.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/alpha/kernel/smp.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
    index 4b2575f936d4..cb64e4797d2a 100644
    --- a/arch/alpha/kernel/smp.c
    +++ b/arch/alpha/kernel/smp.c
    @@ -582,7 +582,7 @@ void
    smp_send_stop(void)
    {
    cpumask_t to_whom;
    - cpumask_copy(&to_whom, cpu_possible_mask);
    + cpumask_copy(&to_whom, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &to_whom);
    #ifdef DEBUG_IPI_MSG
    if (hard_smp_processor_id() != boot_cpu_id)
    --
    2.30.2


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