Merge tag 'md-3.3-fixes' of git://neil.brown.name/md

[platform/adaptation/renesas_rcar/renesas_kernel.git] / kernel / rcutree_plugin.h

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index adb6e66..8bb35d7 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1165,8 +1165,6 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp)
 
 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 
-static struct lock_class_key rcu_boost_class;
-
 /*
  * Carry out RCU priority boosting on the task indicated by ->exp_tasks
  * or ->boost_tasks, advancing the pointer to the next task in the
@@ -1229,15 +1227,13 @@ static int rcu_boost(struct rcu_node *rnp)
         */
        t = container_of(tb, struct task_struct, rcu_node_entry);
        rt_mutex_init_proxy_locked(&mtx, t);
-       /* Avoid lockdep false positives.  This rt_mutex is its own thing. */
-       lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class,
-                                  "rcu_boost_mutex");
        t->rcu_boost_mutex = &mtx;
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
        rt_mutex_lock(&mtx);  /* Side effect: boosts task t's priority. */
        rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
 
-       return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL;
+       return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
+              ACCESS_ONCE(rnp->boost_tasks) != NULL;
 }
 
 /*
@@ -1994,8 +1990,40 @@ static void rcu_prepare_for_idle(int cpu)
 
 #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */
 
-#define RCU_NEEDS_CPU_FLUSHES 5                /* Allow for callback self-repost. */
+/*
+ * This code is invoked when a CPU goes idle, at which point we want
+ * to have the CPU do everything required for RCU so that it can enter
+ * the energy-efficient dyntick-idle mode.  This is handled by a
+ * state machine implemented by rcu_prepare_for_idle() below.
+ *
+ * The following three proprocessor symbols control this state machine:
+ *
+ * RCU_IDLE_FLUSHES gives the maximum number of times that we will attempt
+ *     to satisfy RCU.  Beyond this point, it is better to incur a periodic
+ *     scheduling-clock interrupt than to loop through the state machine
+ *     at full power.
+ * RCU_IDLE_OPT_FLUSHES gives the number of RCU_IDLE_FLUSHES that are
+ *     optional if RCU does not need anything immediately from this
+ *     CPU, even if this CPU still has RCU callbacks queued.  The first
+ *     times through the state machine are mandatory: we need to give
+ *     the state machine a chance to communicate a quiescent state
+ *     to the RCU core.
+ * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted
+ *     to sleep in dyntick-idle mode with RCU callbacks pending.  This
+ *     is sized to be roughly one RCU grace period.  Those energy-efficiency
+ *     benchmarkers who might otherwise be tempted to set this to a large
+ *     number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your
+ *     system.  And if you are -that- concerned about energy efficiency,
+ *     just power the system down and be done with it!
+ *
+ * The values below work well in practice.  If future workloads require
+ * adjustment, they can be converted into kernel config parameters, though
+ * making the state machine smarter might be a better option.
+ */
+#define RCU_IDLE_FLUSHES 5             /* Number of dyntick-idle tries. */
+#define RCU_IDLE_OPT_FLUSHES 3         /* Optional dyntick-idle tries. */
 #define RCU_IDLE_GP_DELAY 6            /* Roughly one grace period. */
+
 static DEFINE_PER_CPU(int, rcu_dyntick_drain);
 static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff);
 static DEFINE_PER_CPU(struct hrtimer, rcu_idle_gp_timer);
@@ -2110,17 +2138,17 @@ static void rcu_prepare_for_idle(int cpu)
        /* Check and update the rcu_dyntick_drain sequencing. */
        if (per_cpu(rcu_dyntick_drain, cpu) <= 0) {
                /* First time through, initialize the counter. */
-               per_cpu(rcu_dyntick_drain, cpu) = RCU_NEEDS_CPU_FLUSHES;
-       } else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
+               per_cpu(rcu_dyntick_drain, cpu) = RCU_IDLE_FLUSHES;
+       } else if (per_cpu(rcu_dyntick_drain, cpu) <= RCU_IDLE_OPT_FLUSHES &&
+                  !rcu_pending(cpu)) {
                /* Can we go dyntick-idle despite still having callbacks? */
-               if (!rcu_pending(cpu)) {
-                       trace_rcu_prep_idle("Dyntick with callbacks");
-                       per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
-                       hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
-                                     rcu_idle_gp_wait, HRTIMER_MODE_REL);
-                       return; /* Nothing more to do immediately. */
-               }
-
+               trace_rcu_prep_idle("Dyntick with callbacks");
+               per_cpu(rcu_dyntick_drain, cpu) = 0;
+               per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
+               hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
+                             rcu_idle_gp_wait, HRTIMER_MODE_REL);
+               return; /* Nothing more to do immediately. */
+       } else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
                /* We have hit the limit, so time to give up. */
                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
                local_irq_restore(flags);