1 files changed, 44 insertions, 179 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 3e4899459f3d..7f3244c0df01 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -68,17 +68,21 @@ static void __init rcu_bootup_announce_oddness(void)
         printk(KERN_INFO "\tAdditional per-CPU info printed with stalls.\n");
 #endif
 #if NUM_RCU_LVL_4 != 0
-        printk(KERN_INFO "\tExperimental four-level hierarchy is enabled.\n");
+        printk(KERN_INFO "\tFour-level hierarchy is enabled.\n");
 #endif
+        if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF)
+                printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
+        if (nr_cpu_ids != NR_CPUS)
+                printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
 }
 
 #ifdef CONFIG_TREE_PREEMPT_RCU
 
-struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt);
+struct rcu_state rcu_preempt_state =
+        RCU_STATE_INITIALIZER(rcu_preempt, call_rcu);
 DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
 static struct rcu_state *rcu_state = &rcu_preempt_state;
 
-static void rcu_read_unlock_special(struct task_struct *t);
 static int rcu_preempted_readers_exp(struct rcu_node *rnp);
 
 /*
@@ -233,18 +237,6 @@ static void rcu_preempt_note_context_switch(int cpu)
 }
 
 /*
- * Tree-preemptible RCU implementation for rcu_read_lock().
- * Just increment ->rcu_read_lock_nesting, shared state will be updated
- * if we block.
- */
-void __rcu_read_lock(void)
-{
-        current->rcu_read_lock_nesting++;
-        barrier();  /* needed if we ever invoke rcu_read_lock in rcutree.c */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_lock);
-
-/*
  * Check for preempted RCU readers blocking the current grace period
  * for the specified rcu_node structure.  If the caller needs a reliable
  * answer, it must hold the rcu_node's ->lock.
@@ -310,7 +302,7 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t,
  * notify RCU core processing or task having blocked during the RCU
  * read-side critical section.
  */
-static noinline void rcu_read_unlock_special(struct task_struct *t)
+void rcu_read_unlock_special(struct task_struct *t)
 {
         int empty;
         int empty_exp;
@@ -398,8 +390,9 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
                                                          rnp->grphi,
                                                          !!rnp->gp_tasks);
                         rcu_report_unblock_qs_rnp(rnp, flags);
-                } else
+                } else {
                         raw_spin_unlock_irqrestore(&rnp->lock, flags);
+                }
 
 #ifdef CONFIG_RCU_BOOST
                 /* Unboost if we were boosted. */
@@ -418,38 +411,6 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
         }
 }
 
-/*
- * Tree-preemptible RCU implementation for rcu_read_unlock().
- * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
- * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
- * invoke rcu_read_unlock_special() to clean up after a context switch
- * in an RCU read-side critical section and other special cases.
- */
-void __rcu_read_unlock(void)
-{
-        struct task_struct *t = current;
-
-        if (t->rcu_read_lock_nesting != 1)
-                --t->rcu_read_lock_nesting;
-        else {
-                barrier();  /* critical section before exit code. */
-                t->rcu_read_lock_nesting = INT_MIN;
-                barrier();  /* assign before ->rcu_read_unlock_special load */
-                if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
-                        rcu_read_unlock_special(t);
-                barrier();  /* ->rcu_read_unlock_special load before assign */
-                t->rcu_read_lock_nesting = 0;
-        }
-#ifdef CONFIG_PROVE_LOCKING
-        {
-                int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
-
-                WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
-        }
-#endif /* #ifdef CONFIG_PROVE_LOCKING */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_unlock);
-
 #ifdef CONFIG_RCU_CPU_STALL_VERBOSE
 
 /*
@@ -540,16 +501,6 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
 }
 
 /*
- * Suppress preemptible RCU's CPU stall warnings by pushing the
- * time of the next stall-warning message comfortably far into the
- * future.
- */
-static void rcu_preempt_stall_reset(void)
-{
-        rcu_preempt_state.jiffies_stall = jiffies + ULONG_MAX / 2;
-}
-
-/*
  * Check that the list of blocked tasks for the newly completed grace
  * period is in fact empty.  It is a serious bug to complete a grace
  * period that still has RCU readers blocked!  This function must be
@@ -650,14 +601,6 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
 /*
- * Do CPU-offline processing for preemptible RCU.
- */
-static void rcu_preempt_cleanup_dead_cpu(int cpu)
-{
-        rcu_cleanup_dead_cpu(cpu, &rcu_preempt_state);
-}
-
-/*
  * Check for a quiescent state from the current CPU.  When a task blocks,
  * the task is recorded in the corresponding CPU's rcu_node structure,
  * which is checked elsewhere.
@@ -677,15 +620,6 @@ static void rcu_preempt_check_callbacks(int cpu)
                 t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
 }
 
-/*
- * Process callbacks for preemptible RCU.
- */
-static void rcu_preempt_process_callbacks(void)
-{
-        __rcu_process_callbacks(&rcu_preempt_state,
-                                &__get_cpu_var(rcu_preempt_data));
-}
-
 #ifdef CONFIG_RCU_BOOST
 
 static void rcu_preempt_do_callbacks(void)
@@ -824,9 +758,9 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
         int must_wait = 0;
 
         raw_spin_lock_irqsave(&rnp->lock, flags);
-        if (list_empty(&rnp->blkd_tasks))
+        if (list_empty(&rnp->blkd_tasks)) {
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
-        else {
+        } else {
                 rnp->exp_tasks = rnp->blkd_tasks.next;
                 rcu_initiate_boost(rnp, flags);  /* releases rnp->lock */
                 must_wait = 1;
@@ -870,9 +804,9 @@ void synchronize_rcu_expedited(void)
          * expedited grace period for us, just leave.
          */
         while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
-                if (trycount++ < 10)
+                if (trycount++ < 10) {
                         udelay(trycount * num_online_cpus());
-                else {
+                } else {
                         synchronize_rcu();
                         return;
                 }
@@ -917,51 +851,16 @@ mb_ret:
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
 
-/*
- * Check to see if there is any immediate preemptible-RCU-related work
- * to be done.
- */
-static int rcu_preempt_pending(int cpu)
-{
-        return __rcu_pending(&rcu_preempt_state,
-                             &per_cpu(rcu_preempt_data, cpu));
-}
-
-/*
- * Does preemptible RCU have callbacks on this CPU?
- */
-static int rcu_preempt_cpu_has_callbacks(int cpu)
-{
-        return !!per_cpu(rcu_preempt_data, cpu).nxtlist;
-}
-
 /**
  * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
  */
 void rcu_barrier(void)
 {
-        _rcu_barrier(&rcu_preempt_state, call_rcu);
+        _rcu_barrier(&rcu_preempt_state);
 }
 EXPORT_SYMBOL_GPL(rcu_barrier);
 
 /*
- * Initialize preemptible RCU's per-CPU data.
- */
-static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
-{
-        rcu_init_percpu_data(cpu, &rcu_preempt_state, 1);
-}
-
-/*
- * Move preemptible RCU's callbacks from dying CPU to other online CPU
- * and record a quiescent state.
- */
-static void rcu_preempt_cleanup_dying_cpu(void)
-{
-        rcu_cleanup_dying_cpu(&rcu_preempt_state);
-}
-
-/*
  * Initialize preemptible RCU's state structures.
  */
 static void __init __rcu_init_preempt(void)
@@ -1046,14 +945,6 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
 }
 
 /*
- * Because preemptible RCU does not exist, there is no need to suppress
- * its CPU stall warnings.
- */
-static void rcu_preempt_stall_reset(void)
-{
-}
-
-/*
  * Because there is no preemptible RCU, there can be no readers blocked,
  * so there is no need to check for blocked tasks.  So check only for
  * bogus qsmask values.
@@ -1081,14 +972,6 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
 /*
- * Because preemptible RCU does not exist, it never needs CPU-offline
- * processing.
- */
-static void rcu_preempt_cleanup_dead_cpu(int cpu)
-{
-}
-
-/*
  * Because preemptible RCU does not exist, it never has any callbacks
  * to check.
  */
@@ -1097,14 +980,6 @@ static void rcu_preempt_check_callbacks(int cpu)
 }
 
 /*
- * Because preemptible RCU does not exist, it never has any callbacks
- * to process.
- */
-static void rcu_preempt_process_callbacks(void)
-{
-}
-
-/*
  * Queue an RCU callback for lazy invocation after a grace period.
  * This will likely be later named something like "call_rcu_lazy()",
  * but this change will require some way of tagging the lazy RCU
@@ -1145,22 +1020,6 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
 /*
- * Because preemptible RCU does not exist, it never has any work to do.
- */
-static int rcu_preempt_pending(int cpu)
-{
-        return 0;
-}
-
-/*
- * Because preemptible RCU does not exist, it never has callbacks
- */
-static int rcu_preempt_cpu_has_callbacks(int cpu)
-{
-        return 0;
-}
-
-/*
  * Because preemptible RCU does not exist, rcu_barrier() is just
  * another name for rcu_barrier_sched().
  */
@@ -1171,21 +1030,6 @@ void rcu_barrier(void)
 EXPORT_SYMBOL_GPL(rcu_barrier);
 
 /*
- * Because preemptible RCU does not exist, there is no per-CPU
- * data to initialize.
- */
-static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
-{
-}
-
-/*
- * Because there is no preemptible RCU, there is no cleanup to do.
- */
-static void rcu_preempt_cleanup_dying_cpu(void)
-{
-}
-
-/*
  * Because preemptible RCU does not exist, it need not be initialized.
  */
 static void __init __rcu_init_preempt(void)
@@ -1968,9 +1812,11 @@ static void rcu_idle_count_callbacks_posted(void)
  */
 #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. */
+#define RCU_IDLE_GP_DELAY 4             /* Roughly one grace period. */
 #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */
 
+extern int tick_nohz_enabled;
+
 /*
  * Does the specified flavor of RCU have non-lazy callbacks pending on
  * the specified CPU?  Both RCU flavor and CPU are specified by the
@@ -2047,10 +1893,13 @@ int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
                 return 1;
         }
         /* Set up for the possibility that RCU will post a timer. */
-        if (rcu_cpu_has_nonlazy_callbacks(cpu))
-                *delta_jiffies = RCU_IDLE_GP_DELAY;
-        else
-                *delta_jiffies = RCU_IDLE_LAZY_GP_DELAY;
+        if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
+                *delta_jiffies = round_up(RCU_IDLE_GP_DELAY + jiffies,
+                                          RCU_IDLE_GP_DELAY) - jiffies;
+        } else {
+                *delta_jiffies = jiffies + RCU_IDLE_LAZY_GP_DELAY;
+                *delta_jiffies = round_jiffies(*delta_jiffies) - jiffies;
+        }
         return 0;
 }
 
@@ -2109,6 +1958,7 @@ static void rcu_cleanup_after_idle(int cpu)
 
         del_timer(&rdtp->idle_gp_timer);
         trace_rcu_prep_idle("Cleanup after idle");
+        rdtp->tick_nohz_enabled_snap = ACCESS_ONCE(tick_nohz_enabled);
 }
 
 /*
@@ -2134,6 +1984,18 @@ static void rcu_prepare_for_idle(int cpu)
 {
         struct timer_list *tp;
         struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+        int tne;
+
+        /* Handle nohz enablement switches conservatively. */
+        tne = ACCESS_ONCE(tick_nohz_enabled);
+        if (tne != rdtp->tick_nohz_enabled_snap) {
+                if (rcu_cpu_has_callbacks(cpu))
+                        invoke_rcu_core(); /* force nohz to see update. */
+                rdtp->tick_nohz_enabled_snap = tne;
+                return;
+        }
+        if (!tne)
+                return;
 
         /*
          * If this is an idle re-entry, for example, due to use of
@@ -2187,10 +2049,11 @@ static void rcu_prepare_for_idle(int cpu)
                 if (rcu_cpu_has_nonlazy_callbacks(cpu)) {
                         trace_rcu_prep_idle("Dyntick with callbacks");
                         rdtp->idle_gp_timer_expires =
-                                           jiffies + RCU_IDLE_GP_DELAY;
+                                round_up(jiffies + RCU_IDLE_GP_DELAY,
+                                         RCU_IDLE_GP_DELAY);
                 } else {
                         rdtp->idle_gp_timer_expires =
-                                           jiffies + RCU_IDLE_LAZY_GP_DELAY;
+                                round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY);
                         trace_rcu_prep_idle("Dyntick with lazy callbacks");
                 }
                 tp = &rdtp->idle_gp_timer;
@@ -2231,8 +2094,9 @@ static void rcu_prepare_for_idle(int cpu)
         if (rcu_cpu_has_callbacks(cpu)) {
                 trace_rcu_prep_idle("More callbacks");
                 invoke_rcu_core();
-        } else
+        } else {
                 trace_rcu_prep_idle("Callbacks drained");
+        }
 }
 
 /*
@@ -2269,6 +2133,7 @@ static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 
 static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 {
+        *cp = '\0';
 }
 
 #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */