Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull v3.14 RCU updates from Paul E. McKenney.

The main changes:

  * Update RCU documentation.

  * Miscellaneous fixes.

  * Add RCU torture scripts.

  * Static-analysis improvements.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 65 insertions, 14 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index dd081987a8ec..e37bd561c26f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -369,6 +369,9 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
 static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
                                 bool user)
 {
+        struct rcu_state *rsp;
+        struct rcu_data *rdp;
+
         trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
         if (!user && !is_idle_task(current)) {
                 struct task_struct *idle __maybe_unused =
@@ -380,6 +383,10 @@ static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
                           current->pid, current->comm,
                           idle->pid, idle->comm); /* must be idle task! */
         }
+        for_each_rcu_flavor(rsp) {
+                rdp = this_cpu_ptr(rsp->rda);
+                do_nocb_deferred_wakeup(rdp);
+        }
         rcu_prepare_for_idle(smp_processor_id());
         /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
         smp_mb__before_atomic_inc();  /* See above. */
@@ -411,11 +418,12 @@ static void rcu_eqs_enter(bool user)
         rdtp = this_cpu_ptr(&rcu_dynticks);
         oldval = rdtp->dynticks_nesting;
         WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
-        if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE)
+        if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) {
                 rdtp->dynticks_nesting = 0;
-        else
+                rcu_eqs_enter_common(rdtp, oldval, user);
+        } else {
                 rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
-        rcu_eqs_enter_common(rdtp, oldval, user);
+        }
 }
 
 /**
@@ -533,11 +541,12 @@ static void rcu_eqs_exit(bool user)
         rdtp = this_cpu_ptr(&rcu_dynticks);
         oldval = rdtp->dynticks_nesting;
         WARN_ON_ONCE(oldval < 0);
-        if (oldval & DYNTICK_TASK_NEST_MASK)
+        if (oldval & DYNTICK_TASK_NEST_MASK) {
                 rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
-        else
+        } else {
                 rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
-        rcu_eqs_exit_common(rdtp, oldval, user);
+                rcu_eqs_exit_common(rdtp, oldval, user);
+        }
 }
 
 /**
@@ -716,7 +725,7 @@ bool rcu_lockdep_current_cpu_online(void)
         bool ret;
 
         if (in_nmi())
-                return 1;
+                return true;
         preempt_disable();
         rdp = this_cpu_ptr(&rcu_sched_data);
         rnp = rdp->mynode;
@@ -755,6 +764,12 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp,
 }
 
 /*
+ * This function really isn't for public consumption, but RCU is special in
+ * that context switches can allow the state machine to make progress.
+ */
+extern void resched_cpu(int cpu);
+
+/*
  * Return true if the specified CPU has passed through a quiescent
  * state by virtue of being in or having passed through an dynticks
  * idle state since the last call to dyntick_save_progress_counter()
@@ -812,16 +827,34 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
          */
         rcu_kick_nohz_cpu(rdp->cpu);
 
+        /*
+         * Alternatively, the CPU might be running in the kernel
+         * for an extended period of time without a quiescent state.
+         * Attempt to force the CPU through the scheduler to gain the
+         * needed quiescent state, but only if the grace period has gone
+         * on for an uncommonly long time.  If there are many stuck CPUs,
+         * we will beat on the first one until it gets unstuck, then move
+         * to the next.  Only do this for the primary flavor of RCU.
+         */
+        if (rdp->rsp == rcu_state &&
+            ULONG_CMP_GE(ACCESS_ONCE(jiffies), rdp->rsp->jiffies_resched)) {
+                rdp->rsp->jiffies_resched += 5;
+                resched_cpu(rdp->cpu);
+        }
+
         return 0;
 }
 
 static void record_gp_stall_check_time(struct rcu_state *rsp)
 {
         unsigned long j = ACCESS_ONCE(jiffies);
+        unsigned long j1;
 
         rsp->gp_start = j;
         smp_wmb(); /* Record start time before stall time. */
-        rsp->jiffies_stall = j + rcu_jiffies_till_stall_check();
+        j1 = rcu_jiffies_till_stall_check();
+        rsp->jiffies_stall = j + j1;
+        rsp->jiffies_resched = j + j1 / 2;
 }
 
 /*
@@ -1509,6 +1542,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
                 rdp = this_cpu_ptr(rsp->rda);
                 if (rnp == rdp->mynode)
                         __note_gp_changes(rsp, rnp, rdp);
+                /* smp_mb() provided by prior unlock-lock pair. */
                 nocb += rcu_future_gp_cleanup(rsp, rnp);
                 raw_spin_unlock_irq(&rnp->lock);
                 cond_resched();
@@ -1553,6 +1587,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
                         wait_event_interruptible(rsp->gp_wq,
                                                  ACCESS_ONCE(rsp->gp_flags) &
                                                  RCU_GP_FLAG_INIT);
+                        /* Locking provides needed memory barrier. */
                         if (rcu_gp_init(rsp))
                                 break;
                         cond_resched();
@@ -1582,6 +1617,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
                                         (!ACCESS_ONCE(rnp->qsmask) &&
                                          !rcu_preempt_blocked_readers_cgp(rnp)),
                                         j);
+                        /* Locking provides needed memory barriers. */
                         /* If grace period done, leave loop. */
                         if (!ACCESS_ONCE(rnp->qsmask) &&
                             !rcu_preempt_blocked_readers_cgp(rnp))
@@ -1901,13 +1937,13 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
  * Adopt the RCU callbacks from the specified rcu_state structure's
  * orphanage.  The caller must hold the ->orphan_lock.
  */
-static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
+static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
 {
         int i;
         struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
 
         /* No-CBs CPUs are handled specially. */
-        if (rcu_nocb_adopt_orphan_cbs(rsp, rdp))
+        if (rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
                 return;
 
         /* Do the accounting first. */
@@ -1986,7 +2022,7 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
 
         /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
         rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
-        rcu_adopt_orphan_cbs(rsp);
+        rcu_adopt_orphan_cbs(rsp, flags);
 
         /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
         mask = rdp->grpmask;    /* rnp->grplo is constant. */
@@ -2303,6 +2339,9 @@ __rcu_process_callbacks(struct rcu_state *rsp)
         /* If there are callbacks ready, invoke them. */
         if (cpu_has_callbacks_ready_to_invoke(rdp))
                 invoke_rcu_callbacks(rsp, rdp);
+
+        /* Do any needed deferred wakeups of rcuo kthreads. */
+        do_nocb_deferred_wakeup(rdp);
 }
 
 /*
@@ -2437,7 +2476,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
 
                 if (cpu != -1)
                         rdp = per_cpu_ptr(rsp->rda, cpu);
-                offline = !__call_rcu_nocb(rdp, head, lazy);
+                offline = !__call_rcu_nocb(rdp, head, lazy, flags);
                 WARN_ON_ONCE(offline);
                 /* _call_rcu() is illegal on offline CPU; leak the callback. */
                 local_irq_restore(flags);
@@ -2757,6 +2796,10 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
         /* Check for CPU stalls, if enabled. */
         check_cpu_stall(rsp, rdp);
 
+        /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */
+        if (rcu_nohz_full_cpu(rsp))
+                return 0;
+
         /* Is the RCU core waiting for a quiescent state from this CPU? */
         if (rcu_scheduler_fully_active &&
             rdp->qs_pending && !rdp->passed_quiesce) {
@@ -2790,6 +2833,12 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
                 return 1;
         }
 
+        /* Does this CPU need a deferred NOCB wakeup? */
+        if (rcu_nocb_need_deferred_wakeup(rdp)) {
+                rdp->n_rp_nocb_defer_wakeup++;
+                return 1;
+        }
+
         /* nothing to do */
         rdp->n_rp_need_nothing++;
         return 0;
@@ -3214,9 +3263,9 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
 {
         int i;
 
-        for (i = rcu_num_lvls - 1; i > 0; i--)
+        rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
+        for (i = rcu_num_lvls - 2; i >= 0; i--)
                 rsp->levelspread[i] = CONFIG_RCU_FANOUT;
-        rsp->levelspread[0] = rcu_fanout_leaf;
 }
 #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
 static void __init rcu_init_levelspread(struct rcu_state *rsp)
@@ -3346,6 +3395,8 @@ static void __init rcu_init_geometry(void)
         if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
             nr_cpu_ids == NR_CPUS)
                 return;
+        pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n",
+                rcu_fanout_leaf, nr_cpu_ids);
 
         /*
          * Compute number of nodes that can be handled an rcu_node tree