Re: [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle

Paul E. McKenney
2017-08-07T12:40:57Z

On Mon, Aug 07, 2017 at 11:20:10AM +0530, Neeraj Upadhyay wrote:
> Pending cbs check in rcu_prepare_for_idle is inversed
> in the sense that, it should accelerate if there are
> pending cbs; but, the check does the opposite. So,
> fix it.
>
> Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
> Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>

Good catch! Queued for review and testing.

Just out of curiosity, how did you find this one?

Thanx, Paul

> ---
> kernel/rcu/tree_plugin.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 908b309..b8f51df 100644
> --- 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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