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    Subject[PATCH v2 1/3] bfq: Fix the missing barrier in __bfq_entity_update_weight_prio
    Date
    The comment of bfq_group_set_weight says the reading of prio_changed
    should happen before the reading of weight, but a memory barrier is
    missing here. Add it now, to match the smp_wmb() there.

    Signed-off-by: Fam Zheng <zhengfeiran@bytedance.com>
    ---
    block/bfq-wf2q.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
    index c9ba225081ce..05f0bf4a1144 100644
    --- a/block/bfq-wf2q.c
    +++ b/block/bfq-wf2q.c
    @@ -744,6 +744,8 @@ __bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
    }
    #endif

    + /* Matches the smp_wmb() in bfq_group_set_weight. */
    + smp_rmb();
    old_st->wsum -= entity->weight;

    if (entity->new_weight != entity->orig_weight) {
    --
    2.11.0
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