From 395a2f097ebdddf2bfa286b6119f1b231025c2f1 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 10 Jul 2018 14:00:14 -0700 Subject: rcu: Define rcu_all_qs() only in !PREEMPT builds Now that rcu_all_qs() is used only in !PREEMPT builds, move it to tree_plugin.h so that it is defined only in those builds. This in turn means that rcu_momentary_dyntick_idle() is only used in !PREEMPT builds, but it is simply marked __maybe_unused in order to keep it near the rest of the dyntick-idle code. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) (limited to 'kernel/rcu/tree_plugin.h') diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index cd4c1b979446..7add1c297500 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -947,6 +947,45 @@ static void rcu_qs(void) rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); } +/* + * Register an urgently needed quiescent state. If there is an + * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight + * dyntick-idle quiescent state visible to other CPUs, which will in + * some cases serve for expedited as well as normal grace periods. + * Either way, register a lightweight quiescent state. + * + * The barrier() calls are redundant in the common case when this is + * called externally, but just in case this is called from within this + * file. + * + */ +void rcu_all_qs(void) +{ + unsigned long flags; + + if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs)) + return; + preempt_disable(); + /* Load rcu_urgent_qs before other flags. */ + if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) { + preempt_enable(); + return; + } + this_cpu_write(rcu_dynticks.rcu_urgent_qs, false); + barrier(); /* Avoid RCU read-side critical sections leaking down. */ + if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) { + local_irq_save(flags); + rcu_momentary_dyntick_idle(); + local_irq_restore(flags); + } + if (unlikely(raw_cpu_read(rcu_data.cpu_no_qs.b.exp))) + rcu_qs(); + this_cpu_inc(rcu_dynticks.rcu_qs_ctr); + barrier(); /* Avoid RCU read-side critical sections leaking up. */ + preempt_enable(); +} +EXPORT_SYMBOL_GPL(rcu_all_qs); + /* * Note a PREEMPT=n context switch. The caller must have disabled interrupts. */ -- cgit v1.2.3