rcu: priority boosting for TREE_PREEMPT_RCU

Add priority boosting for TREE_PREEMPT_RCU, similar to that for
TINY_PREEMPT_RCU.  This is enabled by the default-off RCU_BOOST
kernel parameter.  The priority to which to boost preempted
RCU readers is controlled by the RCU_BOOST_PRIO kernel parameter
(defaulting to real-time priority 1) and the time to wait before
boosting the readers who are blocking a given grace period is
controlled by the RCU_BOOST_DELAY kernel parameter (defaulting to
500 milliseconds).

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index c0213802d164..8db0cdc7f450 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -135,6 +135,24 @@ struct rcu_node {
                                 /*  if there is no such task.  If there */
                                 /*  is no current expedited grace period, */
                                 /*  then there can cannot be any such task. */
+#ifdef CONFIG_RCU_BOOST
+        struct list_head *boost_tasks;
+                                /* Pointer to first task that needs to be */
+                                /*  priority boosted, or NULL if no priority */
+                                /*  boosting is needed for this rcu_node */
+                                /*  structure.  If there are no tasks */
+                                /*  queued on this rcu_node structure that */
+                                /*  are blocking the current grace period, */
+                                /*  there can be no such task. */
+        unsigned long boost_time;
+                                /* When to start boosting (jiffies). */
+        struct task_struct *boost_kthread_task;
+                                /* kthread that takes care of priority */
+                                /*  boosting for this rcu_node structure. */
+        wait_queue_head_t boost_wq;
+                                /* Wait queue on which to park the boost */
+                                /*  kthread. */
+#endif /* #ifdef CONFIG_RCU_BOOST */
         struct task_struct *node_kthread_task;
                                 /* kthread that takes care of this rcu_node */
                                 /*  structure, for example, awakening the */
@@ -365,7 +383,7 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 static void rcu_bootup_announce(void);
 long rcu_batches_completed(void);
 static void rcu_preempt_note_context_switch(int cpu);
-static int rcu_preempted_readers(struct rcu_node *rnp);
+static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 #ifdef CONFIG_HOTPLUG_CPU
 static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
                                       unsigned long flags);
@@ -392,5 +410,16 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
 static void rcu_preempt_send_cbs_to_online(void);
 static void __init __rcu_init_preempt(void);
 static void rcu_needs_cpu_flush(void);
+static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp);
+static void rcu_initiate_boost(struct rcu_node *rnp);
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
+                                          cpumask_var_t cm);
+static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
+static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
+                                                 struct rcu_node *rnp,
+                                                 int rnp_index);
+#ifdef CONFIG_HOTPLUG_CPU
+static void rcu_stop_boost_kthread(struct rcu_node *rnp);
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
 #endif /* #ifndef RCU_TREE_NONCORE */