1 files changed, 532 insertions, 0 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
new file mode 100644
index 000000000000..47789369ea59
--- /dev/null
+++ b/kernel/rcutree_plugin.h
@@ -0,0 +1,532 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion (tree-based version)
+ * Internal non-public definitions that provide either classic
+ * or preemptable semantics.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright Red Hat, 2009
+ * Copyright IBM Corporation, 2009
+ *
+ * Author: Ingo Molnar <mingo@elte.hu>
+ *	   Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ */
+
+
+#ifdef CONFIG_TREE_PREEMPT_RCU
+
+struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state);
+DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
+
+/*
+ * Tell them what RCU they are running.
+ */
+static inline void rcu_bootup_announce(void)
+{
+	printk(KERN_INFO
+	       "Experimental preemptable hierarchical RCU implementation.\n");
+}
+
+/*
+ * Return the number of RCU-preempt batches processed thus far
+ * for debug and statistics.
+ */
+long rcu_batches_completed_preempt(void)
+{
+	return rcu_preempt_state.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt);
+
+/*
+ * Return the number of RCU batches processed thus far for debug & stats.
+ */
+long rcu_batches_completed(void)
+{
+	return rcu_batches_completed_preempt();
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
+
+/*
+ * 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
+ * while in an RCU read-side critical section.
+ */
+static void rcu_preempt_qs_record(int cpu)
+{
+	struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
+	rdp->passed_quiesc = 1;
+	rdp->passed_quiesc_completed = rdp->completed;
+}
+
+/*
+ * We have entered the scheduler or are between softirqs in ksoftirqd.
+ * If we are in an RCU read-side critical section, we need to reflect
+ * that in the state of the rcu_node structure corresponding to this CPU.
+ * Caller must disable hardirqs.
+ */
+static void rcu_preempt_qs(int cpu)
+{
+	struct task_struct *t = current;
+	int phase;
+	struct rcu_data *rdp;
+	struct rcu_node *rnp;
+
+	if (t->rcu_read_lock_nesting &&
+	    (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
+
+		/* Possibly blocking in an RCU read-side critical section. */
+		rdp = rcu_preempt_state.rda[cpu];
+		rnp = rdp->mynode;
+		spin_lock(&rnp->lock);
+		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
+		t->rcu_blocked_node = rnp;
+
+		/*
+		 * If this CPU has already checked in, then this task
+		 * will hold up the next grace period rather than the
+		 * current grace period.  Queue the task accordingly.
+		 * If the task is queued for the current grace period
+		 * (i.e., this CPU has not yet passed through a quiescent
+		 * state for the current grace period), then as long
+		 * as that task remains queued, the current grace period
+		 * cannot end.
+		 */
+		phase = !(rnp->qsmask & rdp->grpmask) ^ (rnp->gpnum & 0x1);
+		list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]);
+		smp_mb();  /* Ensure later ctxt swtch seen after above. */
+		spin_unlock(&rnp->lock);
+	}
+
+	/*
+	 * Either we were not in an RCU read-side critical section to
+	 * begin with, or we have now recorded that critical section
+	 * globally.  Either way, we can now note a quiescent state
+	 * for this CPU.  Again, if we were in an RCU read-side critical
+	 * section, and if that critical section was blocking the current
+	 * grace period, then the fact that the task has been enqueued
+	 * means that we continue to block the current grace period.
+	 */
+	rcu_preempt_qs_record(cpu);
+	t->rcu_read_unlock_special &= ~(RCU_READ_UNLOCK_NEED_QS |
+					RCU_READ_UNLOCK_GOT_QS);
+}
+
+/*
+ * Tree-preemptable 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)
+{
+	ACCESS_ONCE(current->rcu_read_lock_nesting)++;
+	barrier();  /* needed if we ever invoke rcu_read_lock in rcutree.c */
+}
+EXPORT_SYMBOL_GPL(__rcu_read_lock);
+
+static void rcu_read_unlock_special(struct task_struct *t)
+{
+	int empty;
+	unsigned long flags;
+	unsigned long mask;
+	struct rcu_node *rnp;
+	int special;
+
+	/* NMI handlers cannot block and cannot safely manipulate state. */
+	if (in_nmi())
+		return;
+
+	local_irq_save(flags);
+
+	/*
+	 * If RCU core is waiting for this CPU to exit critical section,
+	 * let it know that we have done so.
+	 */
+	special = t->rcu_read_unlock_special;
+	if (special & RCU_READ_UNLOCK_NEED_QS) {
+		t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
+		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_GOT_QS;
+	}
+
+	/* Hardware IRQ handlers cannot block. */
+	if (in_irq()) {
+		local_irq_restore(flags);
+		return;
+	}
+
+	/* Clean up if blocked during RCU read-side critical section. */
+	if (special & RCU_READ_UNLOCK_BLOCKED) {
+		t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED;
+
+		/*
+		 * Remove this task from the list it blocked on.  The
+		 * task can migrate while we acquire the lock, but at
+		 * most one time.  So at most two passes through loop.
+		 */
+		for (;;) {
+			rnp = t->rcu_blocked_node;
+			spin_lock(&rnp->lock);
+			if (rnp == t->rcu_blocked_node)
+				break;
+			spin_unlock(&rnp->lock);
+		}
+		empty = list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
+		list_del_init(&t->rcu_node_entry);
+		t->rcu_blocked_node = NULL;
+
+		/*
+		 * If this was the last task on the current list, and if
+		 * we aren't waiting on any CPUs, report the quiescent state.
+		 * Note that both cpu_quiet_msk_finish() and cpu_quiet_msk()
+		 * drop rnp->lock and restore irq.
+		 */
+		if (!empty && rnp->qsmask == 0 &&
+		    list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])) {
+			t->rcu_read_unlock_special &=
+				~(RCU_READ_UNLOCK_NEED_QS |
+				  RCU_READ_UNLOCK_GOT_QS);
+			if (rnp->parent == NULL) {
+				/* Only one rcu_node in the tree. */
+				cpu_quiet_msk_finish(&rcu_preempt_state, flags);
+				return;
+			}
+			/* Report up the rest of the hierarchy. */
+			mask = rnp->grpmask;
+			spin_unlock_irqrestore(&rnp->lock, flags);
+			rnp = rnp->parent;
+			spin_lock_irqsave(&rnp->lock, flags);
+			cpu_quiet_msk(mask, &rcu_preempt_state, rnp, flags);
+			return;
+		}
+		spin_unlock(&rnp->lock);
+	}
+	local_irq_restore(flags);
+}
+
+/*
+ * Tree-preemptable 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;
+
+	barrier();  /* needed if we ever invoke rcu_read_unlock in rcutree.c */
+	if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 &&
+	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
+		rcu_read_unlock_special(t);
+}
+EXPORT_SYMBOL_GPL(__rcu_read_unlock);
+
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+
+/*
+ * 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 = rnp->gpnum & 0x1;
+	struct task_struct *t;
+
+	if (!list_empty(&rnp->blocked_tasks[phase])) {
+		spin_lock_irqsave(&rnp->lock, flags);
+		phase = rnp->gpnum & 0x1; /* re-read under lock. */
+		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);
+	}
+}
+
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+
+/*
+ * Check for preempted RCU readers for the specified rcu_node structure.
+ * If the caller needs a reliable answer, it must hold the rcu_node's
+ * >lock.
+ */
+static int rcu_preempted_readers(struct rcu_node *rnp)
+{
+	return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Handle tasklist migration for case in which all CPUs covered by the
+ * specified rcu_node have gone offline.  Move them up to the root
+ * rcu_node.  The reason for not just moving them to the immediate
+ * parent is to remove the need for rcu_read_unlock_special() to
+ * make more than two attempts to acquire the target rcu_node's lock.
+ *
+ * The caller must hold rnp->lock with irqs disabled.
+ */
+static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
+				      struct rcu_node *rnp)
+{
+	int i;
+	struct list_head *lp;
+	struct list_head *lp_root;
+	struct rcu_node *rnp_root = rcu_get_root(rsp);
+	struct task_struct *tp;
+
+	if (rnp == rnp_root) {
+		WARN_ONCE(1, "Last CPU thought to be offlined?");
+		return;  /* Shouldn't happen: at least one CPU online. */
+	}
+
+	/*
+	 * Move tasks up to root rcu_node.  Rely on the fact that the
+	 * root rcu_node can be at most one ahead of the rest of the
+	 * rcu_nodes in terms of gp_num value.  This fact allows us to
+	 * move the blocked_tasks[] array directly, element by element.
+	 */
+	for (i = 0; i < 2; i++) {
+		lp = &rnp->blocked_tasks[i];
+		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 */
+			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 */
+		}
+	}
+}
+
+/*
+ * Do CPU-offline processing for preemptable RCU.
+ */
+static void rcu_preempt_offline_cpu(int cpu)
+{
+	__rcu_offline_cpu(cpu, &rcu_preempt_state);
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
+/*
+ * 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.
+ *
+ * Caller must disable hard irqs.
+ */
+static void rcu_preempt_check_callbacks(int cpu)
+{
+	struct task_struct *t = current;
+
+	if (t->rcu_read_lock_nesting == 0) {
+		t->rcu_read_unlock_special &=
+			~(RCU_READ_UNLOCK_NEED_QS | RCU_READ_UNLOCK_GOT_QS);
+		rcu_preempt_qs_record(cpu);
+		return;
+	}
+	if (per_cpu(rcu_preempt_data, cpu).qs_pending) {
+		if (t->rcu_read_unlock_special & RCU_READ_UNLOCK_GOT_QS) {
+			rcu_preempt_qs_record(cpu);
+			t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_GOT_QS;
+		} else if (!(t->rcu_read_unlock_special &
+			     RCU_READ_UNLOCK_NEED_QS)) {
+			t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
+		}
+	}
+}
+
+/*
+ * Process callbacks for preemptable RCU.
+ */
+static void rcu_preempt_process_callbacks(void)
+{
+	__rcu_process_callbacks(&rcu_preempt_state,
+				&__get_cpu_var(rcu_preempt_data));
+}
+
+/*
+ * Queue a preemptable-RCU callback for invocation after a grace period.
+ */
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_preempt_state);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Check to see if there is any immediate preemptable-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 preemptable RCU need the CPU to stay out of dynticks mode?
+ */
+static int rcu_preempt_needs_cpu(int cpu)
+{
+	return !!per_cpu(rcu_preempt_data, cpu).nxtlist;
+}
+
+/*
+ * Initialize preemptable RCU's per-CPU data.
+ */
+static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
+{
+	rcu_init_percpu_data(cpu, &rcu_preempt_state, 1);
+}
+
+/*
+ * Check for a task exiting while in a preemptable-RCU read-side
+ * critical section, clean up if so.  No need to issue warnings,
+ * as debug_check_no_locks_held() already does this if lockdep
+ * is enabled.
+ */
+void exit_rcu(void)
+{
+	struct task_struct *t = current;
+
+	if (t->rcu_read_lock_nesting == 0)
+		return;
+	t->rcu_read_lock_nesting = 1;
+	rcu_read_unlock();
+}
+
+#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+
+/*
+ * Tell them what RCU they are running.
+ */
+static inline void rcu_bootup_announce(void)
+{
+	printk(KERN_INFO "Hierarchical RCU implementation.\n");
+}
+
+/*
+ * Return the number of RCU batches processed thus far for debug & stats.
+ */
+long rcu_batches_completed(void)
+{
+	return rcu_batches_completed_sched();
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
+
+/*
+ * Because preemptable RCU does not exist, we never have to check for
+ * CPUs being in quiescent states.
+ */
+static void rcu_preempt_qs(int cpu)
+{
+}
+
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+
+/*
+ * 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)
+{
+}
+
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+
+/*
+ * Because preemptable RCU does not exist, there are never any preempted
+ * RCU readers.
+ */
+static int rcu_preempted_readers(struct rcu_node *rnp)
+{
+	return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Because preemptable RCU does not exist, it never needs to migrate
+ * tasks that were blocked within RCU read-side critical sections.
+ */
+static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
+				      struct rcu_node *rnp)
+{
+}
+
+/*
+ * Because preemptable RCU does not exist, it never needs CPU-offline
+ * processing.
+ */
+static void rcu_preempt_offline_cpu(int cpu)
+{
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
+/*
+ * Because preemptable RCU does not exist, it never has any callbacks
+ * to check.
+ */
+void rcu_preempt_check_callbacks(int cpu)
+{
+}
+
+/*
+ * Because preemptable RCU does not exist, it never has any callbacks
+ * to process.
+ */
+void rcu_preempt_process_callbacks(void)
+{
+}
+
+/*
+ * In classic RCU, call_rcu() is just call_rcu_sched().
+ */
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+	call_rcu_sched(head, func);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Because preemptable RCU does not exist, it never has any work to do.
+ */
+static int rcu_preempt_pending(int cpu)
+{
+	return 0;
+}
+
+/*
+ * Because preemptable RCU does not exist, it never needs any CPU.
+ */
+static int rcu_preempt_needs_cpu(int cpu)
+{
+	return 0;
+}
+
+/*
+ * Because preemptable RCU does not exist, there is no per-CPU
+ * data to initialize.
+ */
+static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
+{
+}
+
+#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */