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    Subject[PATCH 4.13 27/35] rcu: Fix up pending cbs check in rcu_prepare_for_idle
    Date
    4.13-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Neeraj Upadhyay <neeraju@codeaurora.org>

    commit 135bd1a230bb69a68c9808a7d25467318900b80a upstream.

    The pending-callbacks check in rcu_prepare_for_idle() is backwards.
    It should accelerate if there are pending callbacks, but the check
    rather uselessly accelerates only if there are no callbacks. This commit
    therefore inverts this check.

    Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
    Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/rcu/tree_plugin.h | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/rcu/tree_plugin.h
    +++ b/kernel/rcu/tree_plugin.h
    @@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
    rdtp->last_accelerate = jiffies;
    for_each_rcu_flavor(rsp) {
    rdp = this_cpu_ptr(rsp->rda);
    - if (rcu_segcblist_pend_cbs(&rdp->cblist))
    + if (!rcu_segcblist_pend_cbs(&rdp->cblist))
    continue;
    rnp = rdp->mynode;
    raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */

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