Merge commit '8700c95adb03' into timers/nohz

The full dynticks tree needs the latest RCU and sched
upstream updates in order to fix some dependencies.

Merge a common upstream merge point that has these
updates.

Conflicts:
	include/linux/perf_event.h
	kernel/rcutree.h
	kernel/rcutree_plugin.h

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 197 insertions, 63 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 1d4ceff793a4..16ea67925015 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -64,7 +64,7 @@
 static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
 static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
 
-#define RCU_STATE_INITIALIZER(sname, cr) { \
+#define RCU_STATE_INITIALIZER(sname, sabbr, cr) { \
         .level = { &sname##_state.node[0] }, \
         .call = cr, \
         .fqs_state = RCU_GP_IDLE, \
@@ -76,13 +76,14 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
         .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
         .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
         .name = #sname, \
+        .abbr = sabbr, \
 }
 
 struct rcu_state rcu_sched_state =
-        RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
+        RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
 DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
 
-struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
+struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
 DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
 
 static struct rcu_state *rcu_state;
@@ -223,6 +224,8 @@ static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
 module_param(jiffies_till_first_fqs, ulong, 0644);
 module_param(jiffies_till_next_fqs, ulong, 0644);
 
+static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
+                                  struct rcu_data *rdp);
 static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
 static void force_quiescent_state(struct rcu_state *rsp);
 static int rcu_pending(int cpu);
@@ -310,6 +313,8 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
 
         if (rcu_gp_in_progress(rsp))
                 return 0;  /* No, a grace period is already in progress. */
+        if (rcu_nocb_needs_gp(rsp))
+                return 1;  /* Yes, a no-CBs CPU needs one. */
         if (!rdp->nxttail[RCU_NEXT_TAIL])
                 return 0;  /* No, this is a no-CBs (or offline) CPU. */
         if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
@@ -1045,10 +1050,11 @@ static void init_callback_list(struct rcu_data *rdp)
 {
         int i;
 
+        if (init_nocb_callback_list(rdp))
+                return;
         rdp->nxtlist = NULL;
         for (i = 0; i < RCU_NEXT_SIZE; i++)
                 rdp->nxttail[i] = &rdp->nxtlist;
-        init_nocb_callback_list(rdp);
 }
 
 /*
@@ -1081,6 +1087,120 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
 }
 
 /*
+ * Trace-event helper function for rcu_start_future_gp() and
+ * rcu_nocb_wait_gp().
+ */
+static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
+                                unsigned long c, char *s)
+{
+        trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
+                                      rnp->completed, c, rnp->level,
+                                      rnp->grplo, rnp->grphi, s);
+}
+
+/*
+ * Start some future grace period, as needed to handle newly arrived
+ * callbacks.  The required future grace periods are recorded in each
+ * rcu_node structure's ->need_future_gp field.
+ *
+ * The caller must hold the specified rcu_node structure's ->lock.
+ */
+static unsigned long __maybe_unused
+rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
+{
+        unsigned long c;
+        int i;
+        struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
+
+        /*
+         * Pick up grace-period number for new callbacks.  If this
+         * grace period is already marked as needed, return to the caller.
+         */
+        c = rcu_cbs_completed(rdp->rsp, rnp);
+        trace_rcu_future_gp(rnp, rdp, c, "Startleaf");
+        if (rnp->need_future_gp[c & 0x1]) {
+                trace_rcu_future_gp(rnp, rdp, c, "Prestartleaf");
+                return c;
+        }
+
+        /*
+         * If either this rcu_node structure or the root rcu_node structure
+         * believe that a grace period is in progress, then we must wait
+         * for the one following, which is in "c".  Because our request
+         * will be noticed at the end of the current grace period, we don't
+         * need to explicitly start one.
+         */
+        if (rnp->gpnum != rnp->completed ||
+            ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) {
+                rnp->need_future_gp[c & 0x1]++;
+                trace_rcu_future_gp(rnp, rdp, c, "Startedleaf");
+                return c;
+        }
+
+        /*
+         * There might be no grace period in progress.  If we don't already
+         * hold it, acquire the root rcu_node structure's lock in order to
+         * start one (if needed).
+         */
+        if (rnp != rnp_root)
+                raw_spin_lock(&rnp_root->lock);
+
+        /*
+         * Get a new grace-period number.  If there really is no grace
+         * period in progress, it will be smaller than the one we obtained
+         * earlier.  Adjust callbacks as needed.  Note that even no-CBs
+         * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed.
+         */
+        c = rcu_cbs_completed(rdp->rsp, rnp_root);
+        for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++)
+                if (ULONG_CMP_LT(c, rdp->nxtcompleted[i]))
+                        rdp->nxtcompleted[i] = c;
+
+        /*
+         * If the needed for the required grace period is already
+         * recorded, trace and leave.
+         */
+        if (rnp_root->need_future_gp[c & 0x1]) {
+                trace_rcu_future_gp(rnp, rdp, c, "Prestartedroot");
+                goto unlock_out;
+        }
+
+        /* Record the need for the future grace period. */
+        rnp_root->need_future_gp[c & 0x1]++;
+
+        /* If a grace period is not already in progress, start one. */
+        if (rnp_root->gpnum != rnp_root->completed) {
+                trace_rcu_future_gp(rnp, rdp, c, "Startedleafroot");
+        } else {
+                trace_rcu_future_gp(rnp, rdp, c, "Startedroot");
+                rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
+        }
+unlock_out:
+        if (rnp != rnp_root)
+                raw_spin_unlock(&rnp_root->lock);
+        return c;
+}
+
+/*
+ * Clean up any old requests for the just-ended grace period.  Also return
+ * whether any additional grace periods have been requested.  Also invoke
+ * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads
+ * waiting for this grace period to complete.
+ */
+static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
+{
+        int c = rnp->completed;
+        int needmore;
+        struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+
+        rcu_nocb_gp_cleanup(rsp, rnp);
+        rnp->need_future_gp[c & 0x1] = 0;
+        needmore = rnp->need_future_gp[(c + 1) & 0x1];
+        trace_rcu_future_gp(rnp, rdp, c, needmore ? "CleanupMore" : "Cleanup");
+        return needmore;
+}
+
+/*
  * If there is room, assign a ->completed number to any callbacks on
  * this CPU that have not already been assigned.  Also accelerate any
  * callbacks that were previously assigned a ->completed number that has
@@ -1139,6 +1259,8 @@ static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
                 rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
                 rdp->nxtcompleted[i] = c;
         }
+        /* Record any needed additional grace periods. */
+        rcu_start_future_gp(rnp, rdp);
 
         /* Trace depending on how much we were able to accelerate. */
         if (!*rdp->nxttail[RCU_WAIT_TAIL])
@@ -1318,9 +1440,9 @@ static int rcu_gp_init(struct rcu_state *rsp)
                 rdp = this_cpu_ptr(rsp->rda);
                 rcu_preempt_check_blocked_tasks(rnp);
                 rnp->qsmask = rnp->qsmaskinit;
-                rnp->gpnum = rsp->gpnum;
+                ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
                 WARN_ON_ONCE(rnp->completed != rsp->completed);
-                rnp->completed = rsp->completed;
+                ACCESS_ONCE(rnp->completed) = rsp->completed;
                 if (rnp == rdp->mynode)
                         rcu_start_gp_per_cpu(rsp, rnp, rdp);
                 rcu_preempt_boost_start_gp(rnp);
@@ -1329,7 +1451,8 @@ static int rcu_gp_init(struct rcu_state *rsp)
                                             rnp->grphi, rnp->qsmask);
                 raw_spin_unlock_irq(&rnp->lock);
 #ifdef CONFIG_PROVE_RCU_DELAY
-                if ((random32() % (rcu_num_nodes * 8)) == 0)
+                if ((prandom_u32() % (rcu_num_nodes * 8)) == 0 &&
+                    system_state == SYSTEM_RUNNING)
                         schedule_timeout_uninterruptible(2);
 #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
                 cond_resched();
@@ -1371,6 +1494,7 @@ int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
 static void rcu_gp_cleanup(struct rcu_state *rsp)
 {
         unsigned long gp_duration;
+        int nocb = 0;
         struct rcu_data *rdp;
         struct rcu_node *rnp = rcu_get_root(rsp);
 
@@ -1400,17 +1524,23 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
          */
         rcu_for_each_node_breadth_first(rsp, rnp) {
                 raw_spin_lock_irq(&rnp->lock);
-                rnp->completed = rsp->gpnum;
+                ACCESS_ONCE(rnp->completed) = rsp->gpnum;
+                rdp = this_cpu_ptr(rsp->rda);
+                if (rnp == rdp->mynode)
+                        __rcu_process_gp_end(rsp, rnp, rdp);
+                nocb += rcu_future_gp_cleanup(rsp, rnp);
                 raw_spin_unlock_irq(&rnp->lock);
                 cond_resched();
         }
         rnp = rcu_get_root(rsp);
         raw_spin_lock_irq(&rnp->lock);
+        rcu_nocb_gp_set(rnp, nocb);
 
         rsp->completed = rsp->gpnum; /* Declare grace period done. */
         trace_rcu_grace_period(rsp->name, rsp->completed, "end");
         rsp->fqs_state = RCU_GP_IDLE;
         rdp = this_cpu_ptr(rsp->rda);
+        rcu_advance_cbs(rsp, rnp, rdp);  /* Reduce false positives below. */
         if (cpu_needs_another_gp(rsp, rdp))
                 rsp->gp_flags = 1;
         raw_spin_unlock_irq(&rnp->lock);
@@ -1486,57 +1616,62 @@ static int __noreturn rcu_gp_kthread(void *arg)
 /*
  * Start a new RCU grace period if warranted, re-initializing the hierarchy
  * in preparation for detecting the next grace period.  The caller must hold
- * the root node's ->lock, which is released before return.  Hard irqs must
- * be disabled.
+ * the root node's ->lock and hard irqs must be disabled.
  *
  * Note that it is legal for a dying CPU (which is marked as offline) to
  * invoke this function.  This can happen when the dying CPU reports its
  * quiescent state.
  */
 static void
-rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
-        __releases(rcu_get_root(rsp)->lock)
+rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
+                      struct rcu_data *rdp)
 {
-        struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
-        struct rcu_node *rnp = rcu_get_root(rsp);
-
-        if (!rsp->gp_kthread ||
-            !cpu_needs_another_gp(rsp, rdp)) {
+        if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) {
                 /*
                  * Either we have not yet spawned the grace-period
                  * task, this CPU does not need another grace period,
                  * or a grace period is already in progress.
                  * Either way, don't start a new grace period.
                  */
-                raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 return;
         }
-
-        /*
-         * Because there is no grace period in progress right now,
-         * any callbacks we have up to this point will be satisfied
-         * by the next grace period.  So this is a good place to
-         * assign a grace period number to recently posted callbacks.
-         */
-        rcu_accelerate_cbs(rsp, rnp, rdp);
-
         rsp->gp_flags = RCU_GP_FLAG_INIT;
-        raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
-
-        /* Ensure that CPU is aware of completion of last grace period. */
-        rcu_process_gp_end(rsp, rdp);
-        local_irq_restore(flags);
 
         /* Wake up rcu_gp_kthread() to start the grace period. */
         wake_up(&rsp->gp_wq);
 }
 
 /*
+ * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's
+ * callbacks.  Note that rcu_start_gp_advanced() cannot do this because it
+ * is invoked indirectly from rcu_advance_cbs(), which would result in
+ * endless recursion -- or would do so if it wasn't for the self-deadlock
+ * that is encountered beforehand.
+ */
+static void
+rcu_start_gp(struct rcu_state *rsp)
+{
+        struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+        struct rcu_node *rnp = rcu_get_root(rsp);
+
+        /*
+         * If there is no grace period in progress right now, any
+         * callbacks we have up to this point will be satisfied by the
+         * next grace period.  Also, advancing the callbacks reduces the
+         * probability of false positives from cpu_needs_another_gp()
+         * resulting in pointless grace periods.  So, advance callbacks
+         * then start the grace period!
+         */
+        rcu_advance_cbs(rsp, rnp, rdp);
+        rcu_start_gp_advanced(rsp, rnp, rdp);
+}
+
+/*
  * Report a full set of quiescent states to the specified rcu_state
  * data structure.  This involves cleaning up after the prior grace
  * period and letting rcu_start_gp() start up the next grace period
- * if one is needed.  Note that the caller must hold rnp->lock, as
- * required by rcu_start_gp(), which will release it.
+ * if one is needed.  Note that the caller must hold rnp->lock, which
+ * is released before return.
  */
 static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
         __releases(rcu_get_root(rsp)->lock)
@@ -2134,7 +2269,8 @@ __rcu_process_callbacks(struct rcu_state *rsp)
         local_irq_save(flags);
         if (cpu_needs_another_gp(rsp, rdp)) {
                 raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
-                rcu_start_gp(rsp, flags);  /* releases above lock */
+                rcu_start_gp(rsp);
+                raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
         } else {
                 local_irq_restore(flags);
         }
@@ -2179,7 +2315,8 @@ static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
 
 static void invoke_rcu_core(void)
 {
-        raise_softirq(RCU_SOFTIRQ);
+        if (cpu_online(smp_processor_id()))
+                raise_softirq(RCU_SOFTIRQ);
 }
 
 /*
@@ -2214,11 +2351,11 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 
                 /* Start a new grace period if one not already started. */
                 if (!rcu_gp_in_progress(rsp)) {
-                        unsigned long nestflag;
                         struct rcu_node *rnp_root = rcu_get_root(rsp);
 
-                        raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
-                        rcu_start_gp(rsp, nestflag);  /* rlses rnp_root->lock */
+                        raw_spin_lock(&rnp_root->lock);
+                        rcu_start_gp(rsp);
+                        raw_spin_unlock(&rnp_root->lock);
                 } else {
                         /* Give the grace period a kick. */
                         rdp->blimit = LONG_MAX;
@@ -2638,19 +2775,27 @@ static int rcu_pending(int cpu)
 }
 
 /*
- * Check to see if any future RCU-related work will need to be done
- * by the current CPU, even if none need be done immediately, returning
- * 1 if so.
+ * Return true if the specified CPU has any callback.  If all_lazy is
+ * non-NULL, store an indication of whether all callbacks are lazy.
+ * (If there are no callbacks, all of them are deemed to be lazy.)
  */
-static int rcu_cpu_has_callbacks(int cpu)
+static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
 {
+        bool al = true;
+        bool hc = false;
+        struct rcu_data *rdp;
         struct rcu_state *rsp;
 
-        /* RCU callbacks either ready or pending? */
-        for_each_rcu_flavor(rsp)
-                if (per_cpu_ptr(rsp->rda, cpu)->nxtlist)
-                        return 1;
-        return 0;
+        for_each_rcu_flavor(rsp) {
+                rdp = per_cpu_ptr(rsp->rda, cpu);
+                if (rdp->qlen != rdp->qlen_lazy)
+                        al = false;
+                if (rdp->nxtlist)
+                        hc = true;
+        }
+        if (all_lazy)
+                *all_lazy = al;
+        return hc;
 }
 
 /*
@@ -2869,7 +3014,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
         rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
         atomic_set(&rdp->dynticks->dynticks,
                    (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
-        rcu_prepare_for_idle_init(cpu);
         raw_spin_unlock(&rnp->lock);            /* irqs remain disabled. */
 
         /* Add CPU to rcu_node bitmasks. */
@@ -2919,7 +3063,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
         struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
         struct rcu_node *rnp = rdp->mynode;
         struct rcu_state *rsp;
-        int ret = NOTIFY_OK;
 
         trace_rcu_utilization("Start CPU hotplug");
         switch (action) {
@@ -2933,21 +3076,12 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
                 rcu_boost_kthread_setaffinity(rnp, -1);
                 break;
         case CPU_DOWN_PREPARE:
-                if (nocb_cpu_expendable(cpu))
-                        rcu_boost_kthread_setaffinity(rnp, cpu);
-                else
-                        ret = NOTIFY_BAD;
+                rcu_boost_kthread_setaffinity(rnp, cpu);
                 break;
         case CPU_DYING:
         case CPU_DYING_FROZEN:
-                /*
-                 * The whole machine is "stopped" except this CPU, so we can
-                 * touch any data without introducing corruption. We send the
-                 * dying CPU's callbacks to an arbitrarily chosen online CPU.
-                 */
                 for_each_rcu_flavor(rsp)
                         rcu_cleanup_dying_cpu(rsp);
-                rcu_cleanup_after_idle(cpu);
                 break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
@@ -2960,7 +3094,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
                 break;
         }
         trace_rcu_utilization("End CPU hotplug");
-        return ret;
+        return NOTIFY_OK;
 }
 
 /*
@@ -3095,6 +3229,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
                         }
                         rnp->level = i;
                         INIT_LIST_HEAD(&rnp->blkd_tasks);
+                        rcu_init_one_nocb(rnp);
                 }
         }
 
@@ -3180,8 +3315,7 @@ void __init rcu_init(void)
         rcu_init_one(&rcu_sched_state, &rcu_sched_data);
         rcu_init_one(&rcu_bh_state, &rcu_bh_data);
         __rcu_init_preempt();
-        rcu_init_nocb();
-         open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+        open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 
         /*
          * We don't need protection against CPU-hotplug here because