On Tue, Feb 23, 2021 at 01:10:09AM +0100, Frederic Weisbecker wrote:
> No need to disarm the nocb_timer if rcu_nocb is polling because it
> shouldn't be armed either.
>
> Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
> Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
> Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
OK, so it does make sense to move that del_timer() under the following
"if" statement, then. ;-)
> ---
> kernel/rcu/tree_plugin.h | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 9da67b0d3997..d8b50ff40e4b 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -2186,18 +2186,18 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
> my_rdp->nocb_gp_gp = needwait_gp;
> my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
> if (bypass) {
> - raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
> - // Avoid race with first bypass CB.
> - if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
> - WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
> - del_timer(&my_rdp->nocb_timer);
> - }
> if (!rcu_nocb_poll) {
> + raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
> + // Avoid race with first bypass CB.
> + if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
> + WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
> + del_timer(&my_rdp->nocb_timer);
> + }
> // At least one child with non-empty ->nocb_bypass, so set
> // timer in order to avoid stranding its callbacks.
> mod_timer(&my_rdp->nocb_bypass_timer, j + 2);
> + raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
> }
> - raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
> }
> if (rcu_nocb_poll) {
> /* Polling, so trace if first poll in the series. */
> --
> 2.25.1
>
