When callbacks are in full flow, the common case is waiting for a grace period, and this grace period will normally take a few jiffies to complete. It therefore isn't all that helpful for __call_rcu_nocb_wake() to do a synchronous wakeup in this case. This commit therefore turns this into a timer-based deferred wakeup of the no-CBs grace-period kthread.
Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/tree_plugin.h | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index aaeb8a658f4b..5db39ce1cae1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1897,22 +1897,13 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone, } else if (len > rdp->qlen_last_fqs_check + qhimark) { /* ... or if many callbacks queued. */ rdp->qlen_last_fqs_check = len; - if (!rdp->nocb_cb_sleep && - rcu_segcblist_ready_cbs(&rdp->cblist)) { - // Already going full tilt, so don't try to rewake. - rcu_nocb_unlock_irqrestore(rdp, flags); - } else { + if (rdp->nocb_cb_sleep || + !rcu_segcblist_ready_cbs(&rdp->cblist)) { rcu_advance_cbs_nowake(rdp->mynode, rdp); - if (!irqs_disabled_flags(flags)) { - wake_nocb_gp(rdp, false, flags); - trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, - TPS("WakeOvf")); - } else { - wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE, - TPS("WakeOvfIsDeferred")); - rcu_nocb_unlock_irqrestore(rdp, flags); - } + wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE, + TPS("WakeOvfIsDeferred")); } + rcu_nocb_unlock_irqrestore(rdp, flags); } else { trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot")); rcu_nocb_unlock_irqrestore(rdp, flags); -- 2.17.1
