From 8c14263d351b4766a040346ee917b8d81583a460 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 7 Nov 2019 01:10:55 -0800 Subject: [PATCH] rcu: React to callback overload by boosting RCU readers RCU priority boosting currently is not applied until the grace period is at least 250 milliseconds old (or the number of milliseconds specified by the CONFIG_RCU_BOOST_DELAY Kconfig option). Although this has worked well, it can result in OOM under conditions of RCU callback flooding. One can argue that the real-time systems using RCU priority boosting should carefully avoid RCU callback flooding, but one can just as well argue that an OOM is a rather obnoxious error message. This commit therefore disables the RCU priority boosting delay when there are excessive numbers of callbacks queued. Signed-off-by: Paul E. McKenney --- 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 0be8fad08daa..4d4637c361b7 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1079,7 +1079,7 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) (rnp->gp_tasks != NULL && rnp->boost_tasks == NULL && rnp->qsmask == 0 && - ULONG_CMP_GE(jiffies, rnp->boost_time))) { + (ULONG_CMP_GE(jiffies, rnp->boost_time) || rcu_state.cbovld))) { if (rnp->exp_tasks == NULL) rnp->boost_tasks = rnp->gp_tasks; raw_spin_unlock_irqrestore_rcu_node(rnp, flags);