1 files changed, 282 insertions, 0 deletions

diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
new file mode 100644
index 000000000000..9f6d9ff2572c
--- /dev/null
+++ b/kernel/rcutiny.c
@@ -0,0 +1,282 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * 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 IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ *              Documentation/RCU
+ */
+#include <linux/moduleparam.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/time.h>
+#include <linux/cpu.h>
+
+/* Global control variables for rcupdate callback mechanism. */
+struct rcu_ctrlblk {
+        struct rcu_head *rcucblist;     /* List of pending callbacks (CBs). */
+        struct rcu_head **donetail;     /* ->next pointer of last "done" CB. */
+        struct rcu_head **curtail;      /* ->next pointer of last CB. */
+};
+
+/* Definition for rcupdate control block. */
+static struct rcu_ctrlblk rcu_ctrlblk = {
+        .donetail       = &rcu_ctrlblk.rcucblist,
+        .curtail        = &rcu_ctrlblk.rcucblist,
+};
+
+static struct rcu_ctrlblk rcu_bh_ctrlblk = {
+        .donetail       = &rcu_bh_ctrlblk.rcucblist,
+        .curtail        = &rcu_bh_ctrlblk.rcucblist,
+};
+
+#ifdef CONFIG_NO_HZ
+
+static long rcu_dynticks_nesting = 1;
+
+/*
+ * Enter dynticks-idle mode, which is an extended quiescent state
+ * if we have fully entered that mode (i.e., if the new value of
+ * dynticks_nesting is zero).
+ */
+void rcu_enter_nohz(void)
+{
+        if (--rcu_dynticks_nesting == 0)
+                rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
+
+/*
+ * Exit dynticks-idle mode, so that we are no longer in an extended
+ * quiescent state.
+ */
+void rcu_exit_nohz(void)
+{
+        rcu_dynticks_nesting++;
+}
+
+#endif /* #ifdef CONFIG_NO_HZ */
+
+/*
+ * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
+ * Also disable irqs to avoid confusion due to interrupt handlers
+ * invoking call_rcu().
+ */
+static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+        if (rcp->rcucblist != NULL &&
+            rcp->donetail != rcp->curtail) {
+                rcp->donetail = rcp->curtail;
+                local_irq_restore(flags);
+                return 1;
+        }
+        local_irq_restore(flags);
+
+        return 0;
+}
+
+/*
+ * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
+ * are at it, given that any rcu quiescent state is also an rcu_bh
+ * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
+ */
+void rcu_sched_qs(int cpu)
+{
+        if (rcu_qsctr_help(&rcu_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk))
+                raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Record an rcu_bh quiescent state.
+ */
+void rcu_bh_qs(int cpu)
+{
+        if (rcu_qsctr_help(&rcu_bh_ctrlblk))
+                raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Check to see if the scheduling-clock interrupt came from an extended
+ * quiescent state, and, if so, tell RCU about it.
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+        if (user ||
+            (idle_cpu(cpu) &&
+             !in_softirq() &&
+             hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+                rcu_sched_qs(cpu);
+        else if (!in_softirq())
+                rcu_bh_qs(cpu);
+}
+
+/*
+ * Helper function for rcu_process_callbacks() that operates on the
+ * specified rcu_ctrlkblk structure.
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+{
+        struct rcu_head *next, *list;
+        unsigned long flags;
+
+        /* If no RCU callbacks ready to invoke, just return. */
+        if (&rcp->rcucblist == rcp->donetail)
+                return;
+
+        /* Move the ready-to-invoke callbacks to a local list. */
+        local_irq_save(flags);
+        list = rcp->rcucblist;
+        rcp->rcucblist = *rcp->donetail;
+        *rcp->donetail = NULL;
+        if (rcp->curtail == rcp->donetail)
+                rcp->curtail = &rcp->rcucblist;
+        rcp->donetail = &rcp->rcucblist;
+        local_irq_restore(flags);
+
+        /* Invoke the callbacks on the local list. */
+        while (list) {
+                next = list->next;
+                prefetch(next);
+                list->func(list);
+                list = next;
+        }
+}
+
+/*
+ * Invoke any callbacks whose grace period has completed.
+ */
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+        __rcu_process_callbacks(&rcu_ctrlblk);
+        __rcu_process_callbacks(&rcu_bh_ctrlblk);
+}
+
+/*
+ * Wait for a grace period to elapse.  But it is illegal to invoke
+ * synchronize_sched() from within an RCU read-side critical section.
+ * Therefore, any legal call to synchronize_sched() is a quiescent
+ * state, and so on a UP system, synchronize_sched() need do nothing.
+ * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
+ * benefits of doing might_sleep() to reduce latency.)
+ *
+ * Cool, huh?  (Due to Josh Triplett.)
+ *
+ * But we want to make this a static inline later.
+ */
+void synchronize_sched(void)
+{
+        cond_resched();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+void synchronize_rcu_bh(void)
+{
+        synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+
+/*
+ * Helper function for call_rcu() and call_rcu_bh().
+ */
+static void __call_rcu(struct rcu_head *head,
+                       void (*func)(struct rcu_head *rcu),
+                       struct rcu_ctrlblk *rcp)
+{
+        unsigned long flags;
+
+        head->func = func;
+        head->next = NULL;
+
+        local_irq_save(flags);
+        *rcp->curtail = head;
+        rcp->curtail = &head->next;
+        local_irq_restore(flags);
+}
+
+/*
+ * Post an RCU callback to be invoked after the end of an RCU grace
+ * period.  But since we have but one CPU, that would be after any
+ * quiescent state.
+ */
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+        __call_rcu(head, func, &rcu_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Post an RCU bottom-half callback to be invoked after any subsequent
+ * quiescent state.
+ */
+void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+        __call_rcu(head, func, &rcu_bh_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+
+void rcu_barrier(void)
+{
+        struct rcu_synchronize rcu;
+
+        init_completion(&rcu.completion);
+        /* Will wake me after RCU finished. */
+        call_rcu(&rcu.head, wakeme_after_rcu);
+        /* Wait for it. */
+        wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+void rcu_barrier_bh(void)
+{
+        struct rcu_synchronize rcu;
+
+        init_completion(&rcu.completion);
+        /* Will wake me after RCU finished. */
+        call_rcu_bh(&rcu.head, wakeme_after_rcu);
+        /* Wait for it. */
+        wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+void rcu_barrier_sched(void)
+{
+        struct rcu_synchronize rcu;
+
+        init_completion(&rcu.completion);
+        /* Will wake me after RCU finished. */
+        call_rcu_sched(&rcu.head, wakeme_after_rcu);
+        /* Wait for it. */
+        wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
+void __init rcu_init(void)
+{
+        open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}