Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (44 commits)
  rcu: Fix accelerated GPs for last non-dynticked CPU
  rcu: Make non-RCU_PROVE_LOCKING rcu_read_lock_sched_held() understand boot
  rcu: Fix accelerated grace periods for last non-dynticked CPU
  rcu: Export rcu_scheduler_active
  rcu: Make rcu_read_lock_sched_held() take boot time into account
  rcu: Make lockdep_rcu_dereference() message less alarmist
  sched, cgroups: Fix module export
  rcu: Add RCU_CPU_STALL_VERBOSE to dump detailed per-task information
  rcu: Fix rcutorture mod_timer argument to delay one jiffy
  rcu: Fix deadlock in TREE_PREEMPT_RCU CPU stall detection
  rcu: Convert to raw_spinlocks
  rcu: Stop overflowing signed integers
  rcu: Use canonical URL for Mathieu's dissertation
  rcu: Accelerate grace period if last non-dynticked CPU
  rcu: Fix citation of Mathieu's dissertation
  rcu: Documentation update for CONFIG_PROVE_RCU
  security: Apply lockdep-based checking to rcu_dereference() uses
  idr: Apply lockdep-based diagnostics to rcu_dereference() uses
  radix-tree: Disable RCU lockdep checking in radix tree
  vfs: Abstract rcu_dereference_check for files-fdtable use
  ...

1 files changed, 205 insertions, 24 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 37fbccdf41d5..464ad2cdee00 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -62,6 +62,15 @@ long rcu_batches_completed(void)
 EXPORT_SYMBOL_GPL(rcu_batches_completed);
 
 /*
+ * Force a quiescent state for preemptible RCU.
+ */
+void rcu_force_quiescent_state(void)
+{
+        force_quiescent_state(&rcu_preempt_state, 0);
+}
+EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
+
+/*
  * Record a preemptable-RCU quiescent state for the specified CPU.  Note
  * that this just means that the task currently running on the CPU is
  * not in a quiescent state.  There might be any number of tasks blocked
@@ -102,7 +111,7 @@ static void rcu_preempt_note_context_switch(int cpu)
                 /* Possibly blocking in an RCU read-side critical section. */
                 rdp = rcu_preempt_state.rda[cpu];
                 rnp = rdp->mynode;
-                spin_lock_irqsave(&rnp->lock, flags);
+                raw_spin_lock_irqsave(&rnp->lock, flags);
                 t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
                 t->rcu_blocked_node = rnp;
 
@@ -123,7 +132,7 @@ static void rcu_preempt_note_context_switch(int cpu)
                 WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
                 phase = (rnp->gpnum + !(rnp->qsmask & rdp->grpmask)) & 0x1;
                 list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]);
-                spin_unlock_irqrestore(&rnp->lock, flags);
+                raw_spin_unlock_irqrestore(&rnp->lock, flags);
         }
 
         /*
@@ -180,7 +189,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
         struct rcu_node *rnp_p;
 
         if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) {
-                spin_unlock_irqrestore(&rnp->lock, flags);
+                raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 return;  /* Still need more quiescent states! */
         }
 
@@ -197,8 +206,8 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
 
         /* Report up the rest of the hierarchy. */
         mask = rnp->grpmask;
-        spin_unlock(&rnp->lock);        /* irqs remain disabled. */
-        spin_lock(&rnp_p->lock);        /* irqs already disabled. */
+        raw_spin_unlock(&rnp->lock);    /* irqs remain disabled. */
+        raw_spin_lock(&rnp_p->lock);    /* irqs already disabled. */
         rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags);
 }
 
@@ -248,10 +257,10 @@ static void rcu_read_unlock_special(struct task_struct *t)
                  */
                 for (;;) {
                         rnp = t->rcu_blocked_node;
-                        spin_lock(&rnp->lock);  /* irqs already disabled. */
+                        raw_spin_lock(&rnp->lock);  /* irqs already disabled. */
                         if (rnp == t->rcu_blocked_node)
                                 break;
-                        spin_unlock(&rnp->lock);  /* irqs remain disabled. */
+                        raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
                 }
                 empty = !rcu_preempted_readers(rnp);
                 empty_exp = !rcu_preempted_readers_exp(rnp);
@@ -265,7 +274,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
                  * Note that rcu_report_unblock_qs_rnp() releases rnp->lock.
                  */
                 if (empty)
-                        spin_unlock_irqrestore(&rnp->lock, flags);
+                        raw_spin_unlock_irqrestore(&rnp->lock, flags);
                 else
                         rcu_report_unblock_qs_rnp(rnp, flags);
 
@@ -295,29 +304,73 @@ void __rcu_read_unlock(void)
         if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 &&
             unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
                 rcu_read_unlock_special(t);
+#ifdef CONFIG_PROVE_LOCKING
+        WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0);
+#endif /* #ifdef CONFIG_PROVE_LOCKING */
 }
 EXPORT_SYMBOL_GPL(__rcu_read_unlock);
 
 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
 
+#ifdef CONFIG_RCU_CPU_STALL_VERBOSE
+
+/*
+ * Dump detailed information for all tasks blocking the current RCU
+ * grace period on the specified rcu_node structure.
+ */
+static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
+{
+        unsigned long flags;
+        struct list_head *lp;
+        int phase;
+        struct task_struct *t;
+
+        if (rcu_preempted_readers(rnp)) {
+                raw_spin_lock_irqsave(&rnp->lock, flags);
+                phase = rnp->gpnum & 0x1;
+                lp = &rnp->blocked_tasks[phase];
+                list_for_each_entry(t, lp, rcu_node_entry)
+                        sched_show_task(t);
+                raw_spin_unlock_irqrestore(&rnp->lock, flags);
+        }
+}
+
+/*
+ * Dump detailed information for all tasks blocking the current RCU
+ * grace period.
+ */
+static void rcu_print_detail_task_stall(struct rcu_state *rsp)
+{
+        struct rcu_node *rnp = rcu_get_root(rsp);
+
+        rcu_print_detail_task_stall_rnp(rnp);
+        rcu_for_each_leaf_node(rsp, rnp)
+                rcu_print_detail_task_stall_rnp(rnp);
+}
+
+#else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
+
+static void rcu_print_detail_task_stall(struct rcu_state *rsp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
+
 /*
  * Scan the current list of tasks blocked within RCU read-side critical
  * sections, printing out the tid of each.
  */
 static void rcu_print_task_stall(struct rcu_node *rnp)
 {
-        unsigned long flags;
         struct list_head *lp;
         int phase;
         struct task_struct *t;
 
         if (rcu_preempted_readers(rnp)) {
-                spin_lock_irqsave(&rnp->lock, flags);
                 phase = rnp->gpnum & 0x1;
                 lp = &rnp->blocked_tasks[phase];
                 list_for_each_entry(t, lp, rcu_node_entry)
                         printk(" P%d", t->pid);
-                spin_unlock_irqrestore(&rnp->lock, flags);
         }
 }
 
@@ -388,11 +441,11 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
                 lp_root = &rnp_root->blocked_tasks[i];
                 while (!list_empty(lp)) {
                         tp = list_entry(lp->next, typeof(*tp), rcu_node_entry);
-                        spin_lock(&rnp_root->lock); /* irqs already disabled */
+                        raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
                         list_del(&tp->rcu_node_entry);
                         tp->rcu_blocked_node = rnp_root;
                         list_add(&tp->rcu_node_entry, lp_root);
-                        spin_unlock(&rnp_root->lock); /* irqs remain disabled */
+                        raw_spin_unlock(&rnp_root->lock); /* irqs remain disabled */
                 }
         }
         return retval;
@@ -516,7 +569,7 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
         unsigned long flags;
         unsigned long mask;
 
-        spin_lock_irqsave(&rnp->lock, flags);
+        raw_spin_lock_irqsave(&rnp->lock, flags);
         for (;;) {
                 if (!sync_rcu_preempt_exp_done(rnp))
                         break;
@@ -525,12 +578,12 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
                         break;
                 }
                 mask = rnp->grpmask;
-                spin_unlock(&rnp->lock); /* irqs remain disabled */
+                raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
                 rnp = rnp->parent;
-                spin_lock(&rnp->lock); /* irqs already disabled */
+                raw_spin_lock(&rnp->lock); /* irqs already disabled */
                 rnp->expmask &= ~mask;
         }
-        spin_unlock_irqrestore(&rnp->lock, flags);
+        raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
 
 /*
@@ -545,11 +598,11 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
 {
         int must_wait;
 
-        spin_lock(&rnp->lock); /* irqs already disabled */
+        raw_spin_lock(&rnp->lock); /* irqs already disabled */
         list_splice_init(&rnp->blocked_tasks[0], &rnp->blocked_tasks[2]);
         list_splice_init(&rnp->blocked_tasks[1], &rnp->blocked_tasks[3]);
         must_wait = rcu_preempted_readers_exp(rnp);
-        spin_unlock(&rnp->lock); /* irqs remain disabled */
+        raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
         if (!must_wait)
                 rcu_report_exp_rnp(rsp, rnp);
 }
@@ -594,13 +647,13 @@ void synchronize_rcu_expedited(void)
         /* force all RCU readers onto blocked_tasks[]. */
         synchronize_sched_expedited();
 
-        spin_lock_irqsave(&rsp->onofflock, flags);
+        raw_spin_lock_irqsave(&rsp->onofflock, flags);
 
         /* Initialize ->expmask for all non-leaf rcu_node structures. */
         rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) {
-                spin_lock(&rnp->lock); /* irqs already disabled. */
+                raw_spin_lock(&rnp->lock); /* irqs already disabled. */
                 rnp->expmask = rnp->qsmaskinit;
-                spin_unlock(&rnp->lock); /* irqs remain disabled. */
+                raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
         }
 
         /* Snapshot current state of ->blocked_tasks[] lists. */
@@ -609,7 +662,7 @@ void synchronize_rcu_expedited(void)
         if (NUM_RCU_NODES > 1)
                 sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp));
 
-        spin_unlock_irqrestore(&rsp->onofflock, flags);
+        raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
 
         /* Wait for snapshotted ->blocked_tasks[] lists to drain. */
         rnp = rcu_get_root(rsp);
@@ -713,6 +766,16 @@ long rcu_batches_completed(void)
 EXPORT_SYMBOL_GPL(rcu_batches_completed);
 
 /*
+ * Force a quiescent state for RCU, which, because there is no preemptible
+ * RCU, becomes the same as rcu-sched.
+ */
+void rcu_force_quiescent_state(void)
+{
+        rcu_sched_force_quiescent_state();
+}
+EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
+
+/*
  * Because preemptable RCU does not exist, we never have to check for
  * CPUs being in quiescent states.
  */
@@ -734,7 +797,7 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
 /* Because preemptible RCU does not exist, no quieting of tasks. */
 static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
 {
-        spin_unlock_irqrestore(&rnp->lock, flags);
+        raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
 
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
@@ -745,6 +808,14 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
  * Because preemptable RCU does not exist, we never have to check for
  * tasks blocked within RCU read-side critical sections.
  */
+static void rcu_print_detail_task_stall(struct rcu_state *rsp)
+{
+}
+
+/*
+ * Because preemptable RCU does not exist, we never have to check for
+ * tasks blocked within RCU read-side critical sections.
+ */
 static void rcu_print_task_stall(struct rcu_node *rnp)
 {
 }
@@ -884,3 +955,113 @@ static void __init __rcu_init_preempt(void)
 }
 
 #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
+
+#if !defined(CONFIG_RCU_FAST_NO_HZ)
+
+/*
+ * 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.  This function is part of the RCU implementation; it is -not-
+ * an exported member of the RCU API.
+ *
+ * Because we have preemptible RCU, just check whether this CPU needs
+ * any flavor of RCU.  Do not chew up lots of CPU cycles with preemption
+ * disabled in a most-likely vain attempt to cause RCU not to need this CPU.
+ */
+int rcu_needs_cpu(int cpu)
+{
+        return rcu_needs_cpu_quick_check(cpu);
+}
+
+/*
+ * Check to see if we need to continue a callback-flush operations to
+ * allow the last CPU to enter dyntick-idle mode.  But fast dyntick-idle
+ * entry is not configured, so we never do need to.
+ */
+static void rcu_needs_cpu_flush(void)
+{
+}
+
+#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */
+
+#define RCU_NEEDS_CPU_FLUSHES 5
+static DEFINE_PER_CPU(int, rcu_dyntick_drain);
+static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff);
+
+/*
+ * 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.  This function is part of the RCU implementation; it is -not-
+ * an exported member of the RCU API.
+ *
+ * Because we are not supporting preemptible RCU, attempt to accelerate
+ * any current grace periods so that RCU no longer needs this CPU, but
+ * only if all other CPUs are already in dynticks-idle mode.  This will
+ * allow the CPU cores to be powered down immediately, as opposed to after
+ * waiting many milliseconds for grace periods to elapse.
+ *
+ * Because it is not legal to invoke rcu_process_callbacks() with irqs
+ * disabled, we do one pass of force_quiescent_state(), then do a
+ * raise_softirq() to cause rcu_process_callbacks() to be invoked later.
+ * The per-cpu rcu_dyntick_drain variable controls the sequencing.
+ */
+int rcu_needs_cpu(int cpu)
+{
+        int c = 0;
+        int thatcpu;
+
+        /* Don't bother unless we are the last non-dyntick-idle CPU. */
+        for_each_cpu_not(thatcpu, nohz_cpu_mask)
+                if (thatcpu != cpu) {
+                        per_cpu(rcu_dyntick_drain, cpu) = 0;
+                        per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
+                        return rcu_needs_cpu_quick_check(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) {
+                /* We have hit the limit, so time to give up. */
+                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
+                return rcu_needs_cpu_quick_check(cpu);
+        }
+
+        /* Do one step pushing remaining RCU callbacks through. */
+        if (per_cpu(rcu_sched_data, cpu).nxtlist) {
+                rcu_sched_qs(cpu);
+                force_quiescent_state(&rcu_sched_state, 0);
+                c = c || per_cpu(rcu_sched_data, cpu).nxtlist;
+        }
+        if (per_cpu(rcu_bh_data, cpu).nxtlist) {
+                rcu_bh_qs(cpu);
+                force_quiescent_state(&rcu_bh_state, 0);
+                c = c || per_cpu(rcu_bh_data, cpu).nxtlist;
+        }
+
+        /* If RCU callbacks are still pending, RCU still needs this CPU. */
+        if (c) {
+                raise_softirq(RCU_SOFTIRQ);
+                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
+        }
+        return c;
+}
+
+/*
+ * Check to see if we need to continue a callback-flush operations to
+ * allow the last CPU to enter dyntick-idle mode.
+ */
+static void rcu_needs_cpu_flush(void)
+{
+        int cpu = smp_processor_id();
+        unsigned long flags;
+
+        if (per_cpu(rcu_dyntick_drain, cpu) <= 0)
+                return;
+        local_irq_save(flags);
+        (void)rcu_needs_cpu(cpu);
+        local_irq_restore(flags);
+}
+
+#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */