1 files changed, 388 insertions, 0 deletions

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
new file mode 100644
index 000000000000..0c9a934cfec1
--- /dev/null
+++ b/kernel/rcu/tiny.c
@@ -0,0 +1,388 @@
+/*
+ * 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/completion.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/kernel.h>
+#include <linux/export.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>
+#include <linux/prefetch.h>
+#include <linux/ftrace_event.h>
+
+#ifdef CONFIG_RCU_TRACE
+#include <trace/events/rcu.h>
+#endif /* #else #ifdef CONFIG_RCU_TRACE */
+
+#include "rcu.h"
+
+/* Forward declarations for tiny_plugin.h. */
+struct rcu_ctrlblk;
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
+static void rcu_process_callbacks(struct softirq_action *unused);
+static void __call_rcu(struct rcu_head *head,
+                       void (*func)(struct rcu_head *rcu),
+                       struct rcu_ctrlblk *rcp);
+
+static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+
+#include "tiny_plugin.h"
+
+/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
+static void rcu_idle_enter_common(long long newval)
+{
+        if (newval) {
+                RCU_TRACE(trace_rcu_dyntick(TPS("--="),
+                                            rcu_dynticks_nesting, newval));
+                rcu_dynticks_nesting = newval;
+                return;
+        }
+        RCU_TRACE(trace_rcu_dyntick(TPS("Start"),
+                                    rcu_dynticks_nesting, newval));
+        if (!is_idle_task(current)) {
+                struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());
+
+                RCU_TRACE(trace_rcu_dyntick(TPS("Entry error: not idle task"),
+                                            rcu_dynticks_nesting, newval));
+                ftrace_dump(DUMP_ALL);
+                WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                          current->pid, current->comm,
+                          idle->pid, idle->comm); /* must be idle task! */
+        }
+        rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+        barrier();
+        rcu_dynticks_nesting = newval;
+}
+
+/*
+ * Enter idle, 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_idle_enter(void)
+{
+        unsigned long flags;
+        long long newval;
+
+        local_irq_save(flags);
+        WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);
+        if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==
+            DYNTICK_TASK_NEST_VALUE)
+                newval = 0;
+        else
+                newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE;
+        rcu_idle_enter_common(newval);
+        local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
+
+/*
+ * Exit an interrupt handler towards idle.
+ */
+void rcu_irq_exit(void)
+{
+        unsigned long flags;
+        long long newval;
+
+        local_irq_save(flags);
+        newval = rcu_dynticks_nesting - 1;
+        WARN_ON_ONCE(newval < 0);
+        rcu_idle_enter_common(newval);
+        local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_irq_exit);
+
+/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
+static void rcu_idle_exit_common(long long oldval)
+{
+        if (oldval) {
+                RCU_TRACE(trace_rcu_dyntick(TPS("++="),
+                                            oldval, rcu_dynticks_nesting));
+                return;
+        }
+        RCU_TRACE(trace_rcu_dyntick(TPS("End"), oldval, rcu_dynticks_nesting));
+        if (!is_idle_task(current)) {
+                struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());
+
+                RCU_TRACE(trace_rcu_dyntick(TPS("Exit error: not idle task"),
+                          oldval, rcu_dynticks_nesting));
+                ftrace_dump(DUMP_ALL);
+                WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                          current->pid, current->comm,
+                          idle->pid, idle->comm); /* must be idle task! */
+        }
+}
+
+/*
+ * Exit idle, so that we are no longer in an extended quiescent state.
+ */
+void rcu_idle_exit(void)
+{
+        unsigned long flags;
+        long long oldval;
+
+        local_irq_save(flags);
+        oldval = rcu_dynticks_nesting;
+        WARN_ON_ONCE(rcu_dynticks_nesting < 0);
+        if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK)
+                rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
+        else
+                rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+        rcu_idle_exit_common(oldval);
+        local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
+
+/*
+ * Enter an interrupt handler, moving away from idle.
+ */
+void rcu_irq_enter(void)
+{
+        unsigned long flags;
+        long long oldval;
+
+        local_irq_save(flags);
+        oldval = rcu_dynticks_nesting;
+        rcu_dynticks_nesting++;
+        WARN_ON_ONCE(rcu_dynticks_nesting == 0);
+        rcu_idle_exit_common(oldval);
+        local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_irq_enter);
+
+#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)
+
+/*
+ * Test whether RCU thinks that the current CPU is idle.
+ */
+bool __rcu_is_watching(void)
+{
+        return rcu_dynticks_nesting;
+}
+EXPORT_SYMBOL(__rcu_is_watching);
+
+#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
+
+/*
+ * Test whether the current CPU was interrupted from idle.  Nested
+ * interrupts don't count, we must be running at the first interrupt
+ * level.
+ */
+static int rcu_is_cpu_rrupt_from_idle(void)
+{
+        return rcu_dynticks_nesting <= 1;
+}
+
+/*
+ * Helper function for rcu_sched_qs() and rcu_bh_qs().
+ * Also irqs are disabled to avoid confusion due to interrupt handlers
+ * invoking call_rcu().
+ */
+static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+{
+        RCU_TRACE(reset_cpu_stall_ticks(rcp));
+        if (rcp->rcucblist != NULL &&
+            rcp->donetail != rcp->curtail) {
+                rcp->donetail = rcp->curtail;
+                return 1;
+        }
+
+        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)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+        if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
+            rcu_qsctr_help(&rcu_bh_ctrlblk))
+                raise_softirq(RCU_SOFTIRQ);
+        local_irq_restore(flags);
+}
+
+/*
+ * Record an rcu_bh quiescent state.
+ */
+void rcu_bh_qs(int cpu)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+        if (rcu_qsctr_help(&rcu_bh_ctrlblk))
+                raise_softirq(RCU_SOFTIRQ);
+        local_irq_restore(flags);
+}
+
+/*
+ * Check to see if the scheduling-clock interrupt came from an extended
+ * quiescent state, and, if so, tell RCU about it.  This function must
+ * be called from hardirq context.  It is normally called from the
+ * scheduling-clock interrupt.
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+        RCU_TRACE(check_cpu_stalls());
+        if (user || rcu_is_cpu_rrupt_from_idle())
+                rcu_sched_qs(cpu);
+        else if (!in_softirq())
+                rcu_bh_qs(cpu);
+}
+
+/*
+ * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
+ * whose grace period has elapsed.
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+{
+        const char *rn = NULL;
+        struct rcu_head *next, *list;
+        unsigned long flags;
+        RCU_TRACE(int cb_count = 0);
+
+        /* If no RCU callbacks ready to invoke, just return. */
+        if (&rcp->rcucblist == rcp->donetail) {
+                RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1));
+                RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
+                                              !!ACCESS_ONCE(rcp->rcucblist),
+                                              need_resched(),
+                                              is_idle_task(current),
+                                              false));
+                return;
+        }
+
+        /* Move the ready-to-invoke callbacks to a local list. */
+        local_irq_save(flags);
+        RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1));
+        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. */
+        RCU_TRACE(rn = rcp->name);
+        while (list) {
+                next = list->next;
+                prefetch(next);
+                debug_rcu_head_unqueue(list);
+                local_bh_disable();
+                __rcu_reclaim(rn, list);
+                local_bh_enable();
+                list = next;
+                RCU_TRACE(cb_count++);
+        }
+        RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
+        RCU_TRACE(trace_rcu_batch_end(rcp->name,
+                                      cb_count, 0, need_resched(),
+                                      is_idle_task(current),
+                                      false));
+}
+
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+        __rcu_process_callbacks(&rcu_sched_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.  The cond_resched()
+ * currently makes this problematic.
+ */
+void synchronize_sched(void)
+{
+        rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                           !lock_is_held(&rcu_lock_map) &&
+                           !lock_is_held(&rcu_sched_lock_map),
+                           "Illegal synchronize_sched() in RCU read-side critical section");
+        cond_resched();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+/*
+ * 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;
+
+        debug_rcu_head_queue(head);
+        head->func = func;
+        head->next = NULL;
+
+        local_irq_save(flags);
+        *rcp->curtail = head;
+        rcp->curtail = &head->next;
+        RCU_TRACE(rcp->qlen++);
+        local_irq_restore(flags);
+}
+
+/*
+ * Post an RCU callback to be invoked after the end of an RCU-sched grace
+ * period.  But since we have but one CPU, that would be after any
+ * quiescent state.
+ */
+void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+        __call_rcu(head, func, &rcu_sched_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu_sched);
+
+/*
+ * 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_init(void)
+{
+        open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}