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    Subject[PATCH] sched/membarrier: fix missing local execution of ipi_sync_rq_state()
    Date
    The function sync_runqueues_membarrier_state() should copy the
    membarrier state from the @mm received as parameter to each runqueue
    currently running tasks using that mm.

    However, the use of smp_call_function_many() skips the current runqueue,
    which is unintended. Replace by a call to on_each_cpu_mask().

    Fixes: 227a4aadc75b ("sched/membarrier: Fix p->mm->membarrier_state racy load")
    Link: https://lore.kernel.org/r/74F1E842-4A84-47BF-B6C2-5407DFDD4A4A@gmail.com
    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Reported-by: Nadav Amit <nadav.amit@gmail.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Nadav Amit <nadav.amit@gmail.com>
    Cc: stable@vger.kernel.org # 5.4.x+
    ---
    kernel/sched/membarrier.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
    index 08ae45ad9261..f311bf85d211 100644
    --- a/kernel/sched/membarrier.c
    +++ b/kernel/sched/membarrier.c
    @@ -471,9 +471,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm)
    }
    rcu_read_unlock();

    - preempt_disable();
    - smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1);
    - preempt_enable();
    + on_each_cpu_mask(tmpmask, ipi_sync_rq_state, mm, true);

    free_cpumask_var(tmpmask);
    cpus_read_unlock();
    --
    2.17.1
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