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    Subject[RFC v2 2/5] rcu: Use for_each_leaf_node_cpu() in RCU stall checking
    Date
    Use for_each_leaf_node_cpu() in RCU stall checking code, to save some
    extra checks, based on the fact that ->qsmask is mostly more sparse than
    cpu_possible_mask.

    Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
    ---
    kernel/rcu/tree.c | 20 ++++++++++----------
    1 file changed, 10 insertions(+), 10 deletions(-)

    diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
    index b56e2dc31ba5..4e5b81c843de 100644
    --- a/kernel/rcu/tree.c
    +++ b/kernel/rcu/tree.c
    @@ -1417,10 +1417,11 @@ static void rcu_dump_cpu_stacks(struct rcu_state *rsp)

    rcu_for_each_leaf_node(rsp, rnp) {
    raw_spin_lock_irqsave_rcu_node(rnp, flags);
    - for_each_leaf_node_possible_cpu(rnp, cpu)
    - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
    - if (!trigger_single_cpu_backtrace(cpu))
    - dump_cpu_task(cpu);
    +
    + for_each_leaf_node_cpu(rnp, rnp->qsmask, cpu)
    + if (!trigger_single_cpu_backtrace(cpu))
    + dump_cpu_task(cpu);
    +
    raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
    }
    }
    @@ -1490,13 +1491,12 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
    rcu_for_each_leaf_node(rsp, rnp) {
    raw_spin_lock_irqsave_rcu_node(rnp, flags);
    ndetected += rcu_print_task_stall(rnp);
    - if (rnp->qsmask != 0) {
    - for_each_leaf_node_possible_cpu(rnp, cpu)
    - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {
    - print_cpu_stall_info(rsp, cpu);
    - ndetected++;
    - }
    +
    + for_each_leaf_node_cpu(rnp, rnp->qsmask, cpu) {
    + print_cpu_stall_info(rsp, cpu);
    + ndetected++;
    }
    +
    raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
    }

    --
    2.10.2
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