From: Zqiang Date: Fri, 13 May 2022 00:42:55 +0000 (+0800) Subject: rcu: Immediately boost preempted readers for strict grace periods X-Git-Tag: v6.6.17~6938^2~1^2~7 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=70a82c3c55c8665d3996dcb9968adcf24d52bbc4;p=platform%2Fkernel%2Flinux-rpi.git rcu: Immediately boost preempted readers for strict grace periods The intent of the CONFIG_RCU_STRICT_GRACE_PERIOD Konfig option is to cause normal grace periods to complete quickly in order to better catch errors resulting from improperly leaking pointers from RCU read-side critical sections. However, kernels built with this option enabled still wait for some hundreds of milliseconds before boosting RCU readers that have been preempted within their current critical section. The value of this delay is set by the CONFIG_RCU_BOOST_DELAY Kconfig option, which defaults to 500 milliseconds. This commit therefore causes kernels build with strict grace periods to ignore CONFIG_RCU_BOOST_DELAY. This causes rcu_initiate_boost() to start boosting immediately after all CPUs on a given leaf rcu_node structure have passed through their quiescent states. Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney Reviewed-by: Neeraj Upadhyay --- diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 7a07f2c..4c92034 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1140,7 +1140,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) (rnp->gp_tasks != NULL && rnp->boost_tasks == NULL && rnp->qsmask == 0 && - (!time_after(rnp->boost_time, jiffies) || rcu_state.cbovld))) { + (!time_after(rnp->boost_time, jiffies) || rcu_state.cbovld || + IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)))) { if (rnp->exp_tasks == NULL) WRITE_ONCE(rnp->boost_tasks, rnp->gp_tasks); raw_spin_unlock_irqrestore_rcu_node(rnp, flags);