From d28139c4e96713d52a300fb9036c5be2f45e0741 Mon Sep 17 00:00:00 2001 From: Paul E. McKenney Date: Thu, 28 Jun 2018 14:45:25 -0700 Subject: rcu: Apply RCU-bh QSes to RCU-sched and RCU-preempt when safe One necessary step towards consolidating the three flavors of RCU is to make sure that the resulting consolidated "one flavor to rule them all" correctly handles networking denial-of-service attacks. One thing that allows RCU-bh to do so is that __do_softirq() invokes rcu_bh_qs() every so often, and so something similar has to happen for consolidated RCU. This must be done carefully. For example, if a preemption-disabled region of code takes an interrupt which does softirq processing before returning, consolidated RCU must ignore the resulting rcu_bh_qs() invocations -- preemption is still disabled, and that means an RCU reader for the consolidated flavor. This commit therefore creates a new rcu_softirq_qs() that is called only from the ksoftirqd task, thus avoiding the interrupted-a-preempted-region problem. This new rcu_softirq_qs() function invokes rcu_sched_qs(), rcu_preempt_qs(), and rcu_preempt_deferred_qs(). The latter call handles any deferred quiescent states. Note that __do_softirq() still invokes rcu_bh_qs(). It will continue to do so until a later stage of cleanup when the RCU-bh flavor is removed. Signed-off-by: Paul E. McKenney [ paulmck: Fix !SMP issue located by kbuild test robot. ] --- include/linux/rcutiny.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/rcutiny.h') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index f617ab19bb51..bcfbc40a7239 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -90,6 +90,11 @@ static inline void kfree_call_rcu(struct rcu_head *head, call_rcu(head, func); } +static inline void rcu_softirq_qs(void) +{ + rcu_sched_qs(); +} + #define rcu_note_context_switch(preempt) \ do { \ rcu_sched_qs(); \ -- cgit v1.2.3-55-g7522