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    Subject[PATCH 5.4 038/453] kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling
    Date
    From: Nicholas Piggin <npiggin@gmail.com>

    [ Upstream commit 8ff00399b153440c1c83e20c43020385b416415b ]

    powerpc/64s keeps a counter in the mm which counts bits set in
    mm_cpumask as well as other things. This means it can't use generic code
    to clear bits out of the mask and doesn't adjust the arch specific
    counter.

    Add an arch override that allows powerpc/64s to use
    clear_tasks_mm_cpumask().

    Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
    Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
    Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20201126102530.691335-4-npiggin@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/cpu.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/kernel/cpu.c b/kernel/cpu.c
    index 7527825ac7daa..fa0e5727b4d9c 100644
    --- a/kernel/cpu.c
    +++ b/kernel/cpu.c
    @@ -815,6 +815,10 @@ void __init cpuhp_threads_init(void)
    }

    #ifdef CONFIG_HOTPLUG_CPU
    +#ifndef arch_clear_mm_cpumask_cpu
    +#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
    +#endif
    +
    /**
    * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
    * @cpu: a CPU id
    @@ -850,7 +854,7 @@ void clear_tasks_mm_cpumask(int cpu)
    t = find_lock_task_mm(p);
    if (!t)
    continue;
    - cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
    + arch_clear_mm_cpumask_cpu(cpu, t->mm);
    task_unlock(t);
    }
    rcu_read_unlock();
    --
    2.27.0


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