1 files changed, 470 insertions, 0 deletions

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
new file mode 100644
index 000000000000..d00eded75d71
--- /dev/null
+++ b/kernel/rcupdate.c
@@ -0,0 +1,470 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion
+ *
+ * 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 (C) IBM Corporation, 2001
+ *
+ * Authors: Dipankar Sarma <dipankar@in.ibm.com>
+ *          Manfred Spraul <manfred@colorfullife.com>
+ * 
+ * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ * Papers:
+ * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
+ * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ *              http://lse.sourceforge.net/locking/rcupdate.html
+ *
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/cpu.h>
+
+/* Definition for rcupdate control block. */
+struct rcu_ctrlblk rcu_ctrlblk = 
+        { .cur = -300, .completed = -300 };
+struct rcu_ctrlblk rcu_bh_ctrlblk =
+        { .cur = -300, .completed = -300 };
+
+/* Bookkeeping of the progress of the grace period */
+struct rcu_state {
+        spinlock_t      lock; /* Guard this struct and writes to rcu_ctrlblk */
+        cpumask_t       cpumask; /* CPUs that need to switch in order    */
+                                      /* for current batch to proceed.        */
+};
+
+static struct rcu_state rcu_state ____cacheline_maxaligned_in_smp =
+          {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };
+static struct rcu_state rcu_bh_state ____cacheline_maxaligned_in_smp =
+          {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };
+
+DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
+DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
+
+/* Fake initialization required by compiler */
+static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
+static int maxbatch = 10;
+
+/**
+ * call_rcu - Queue an RCU callback for invocation after a grace period.
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual update function to be invoked after the grace period
+ *
+ * The update function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed.  RCU read-side critical
+ * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
+ * and may be nested.
+ */
+void fastcall call_rcu(struct rcu_head *head,
+                                void (*func)(struct rcu_head *rcu))
+{
+        unsigned long flags;
+        struct rcu_data *rdp;
+
+        head->func = func;
+        head->next = NULL;
+        local_irq_save(flags);
+        rdp = &__get_cpu_var(rcu_data);
+        *rdp->nxttail = head;
+        rdp->nxttail = &head->next;
+        local_irq_restore(flags);
+}
+
+/**
+ * call_rcu_bh - Queue an RCU for invocation after a quicker grace period.
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual update function to be invoked after the grace period
+ *
+ * The update function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed. call_rcu_bh() assumes
+ * that the read-side critical sections end on completion of a softirq
+ * handler. This means that read-side critical sections in process
+ * context must not be interrupted by softirqs. This interface is to be
+ * used when most of the read-side critical sections are in softirq context.
+ * RCU read-side critical sections are delimited by rcu_read_lock() and
+ * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh()
+ * and rcu_read_unlock_bh(), if in process context. These may be nested.
+ */
+void fastcall call_rcu_bh(struct rcu_head *head,
+                                void (*func)(struct rcu_head *rcu))
+{
+        unsigned long flags;
+        struct rcu_data *rdp;
+
+        head->func = func;
+        head->next = NULL;
+        local_irq_save(flags);
+        rdp = &__get_cpu_var(rcu_bh_data);
+        *rdp->nxttail = head;
+        rdp->nxttail = &head->next;
+        local_irq_restore(flags);
+}
+
+/*
+ * Invoke the completed RCU callbacks. They are expected to be in
+ * a per-cpu list.
+ */
+static void rcu_do_batch(struct rcu_data *rdp)
+{
+        struct rcu_head *next, *list;
+        int count = 0;
+
+        list = rdp->donelist;
+        while (list) {
+                next = rdp->donelist = list->next;
+                list->func(list);
+                list = next;
+                if (++count >= maxbatch)
+                        break;
+        }
+        if (!rdp->donelist)
+                rdp->donetail = &rdp->donelist;
+        else
+                tasklet_schedule(&per_cpu(rcu_tasklet, rdp->cpu));
+}
+
+/*
+ * Grace period handling:
+ * The grace period handling consists out of two steps:
+ * - A new grace period is started.
+ *   This is done by rcu_start_batch. The start is not broadcasted to
+ *   all cpus, they must pick this up by comparing rcp->cur with
+ *   rdp->quiescbatch. All cpus are recorded  in the
+ *   rcu_state.cpumask bitmap.
+ * - All cpus must go through a quiescent state.
+ *   Since the start of the grace period is not broadcasted, at least two
+ *   calls to rcu_check_quiescent_state are required:
+ *   The first call just notices that a new grace period is running. The
+ *   following calls check if there was a quiescent state since the beginning
+ *   of the grace period. If so, it updates rcu_state.cpumask. If
+ *   the bitmap is empty, then the grace period is completed.
+ *   rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
+ *   period (if necessary).
+ */
+/*
+ * Register a new batch of callbacks, and start it up if there is currently no
+ * active batch and the batch to be registered has not already occurred.
+ * Caller must hold rcu_state.lock.
+ */
+static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp,
+                                int next_pending)
+{
+        if (next_pending)
+                rcp->next_pending = 1;
+
+        if (rcp->next_pending &&
+                        rcp->completed == rcp->cur) {
+                /* Can't change, since spin lock held. */
+                cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask);
+
+                rcp->next_pending = 0;
+                /* next_pending == 0 must be visible in __rcu_process_callbacks()
+                 * before it can see new value of cur.
+                 */
+                smp_wmb();
+                rcp->cur++;
+        }
+}
+
+/*
+ * cpu went through a quiescent state since the beginning of the grace period.
+ * Clear it from the cpu mask and complete the grace period if it was the last
+ * cpu. Start another grace period if someone has further entries pending
+ */
+static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
+{
+        cpu_clear(cpu, rsp->cpumask);
+        if (cpus_empty(rsp->cpumask)) {
+                /* batch completed ! */
+                rcp->completed = rcp->cur;
+                rcu_start_batch(rcp, rsp, 0);
+        }
+}
+
+/*
+ * Check if the cpu has gone through a quiescent state (say context
+ * switch). If so and if it already hasn't done so in this RCU
+ * quiescent cycle, then indicate that it has done so.
+ */
+static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
+                        struct rcu_state *rsp, struct rcu_data *rdp)
+{
+        if (rdp->quiescbatch != rcp->cur) {
+                /* start new grace period: */
+                rdp->qs_pending = 1;
+                rdp->passed_quiesc = 0;
+                rdp->quiescbatch = rcp->cur;
+                return;
+        }
+
+        /* Grace period already completed for this cpu?
+         * qs_pending is checked instead of the actual bitmap to avoid
+         * cacheline trashing.
+         */
+        if (!rdp->qs_pending)
+                return;
+
+        /* 
+         * Was there a quiescent state since the beginning of the grace
+         * period? If no, then exit and wait for the next call.
+         */
+        if (!rdp->passed_quiesc)
+                return;
+        rdp->qs_pending = 0;
+
+        spin_lock(&rsp->lock);
+        /*
+         * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
+         * during cpu startup. Ignore the quiescent state.
+         */
+        if (likely(rdp->quiescbatch == rcp->cur))
+                cpu_quiet(rdp->cpu, rcp, rsp);
+
+        spin_unlock(&rsp->lock);
+}
+
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing
+ * locking requirements, the list it's pulling from has to belong to a cpu
+ * which is dead and hence not processing interrupts.
+ */
+static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list,
+                                struct rcu_head **tail)
+{
+        local_irq_disable();
+        *this_rdp->nxttail = list;
+        if (list)
+                this_rdp->nxttail = tail;
+        local_irq_enable();
+}
+
+static void __rcu_offline_cpu(struct rcu_data *this_rdp,
+        struct rcu_ctrlblk *rcp, struct rcu_state *rsp, struct rcu_data *rdp)
+{
+        /* if the cpu going offline owns the grace period
+         * we can block indefinitely waiting for it, so flush
+         * it here
+         */
+        spin_lock_bh(&rsp->lock);
+        if (rcp->cur != rcp->completed)
+                cpu_quiet(rdp->cpu, rcp, rsp);
+        spin_unlock_bh(&rsp->lock);
+        rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
+        rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
+
+}
+static void rcu_offline_cpu(int cpu)
+{
+        struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
+        struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
+
+        __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, &rcu_state,
+                                        &per_cpu(rcu_data, cpu));
+        __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, &rcu_bh_state,
+                                        &per_cpu(rcu_bh_data, cpu));
+        put_cpu_var(rcu_data);
+        put_cpu_var(rcu_bh_data);
+        tasklet_kill_immediate(&per_cpu(rcu_tasklet, cpu), cpu);
+}
+
+#else
+
+static void rcu_offline_cpu(int cpu)
+{
+}
+
+#endif
+
+/*
+ * This does the RCU processing work from tasklet context. 
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
+                        struct rcu_state *rsp, struct rcu_data *rdp)
+{
+        if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
+                *rdp->donetail = rdp->curlist;
+                rdp->donetail = rdp->curtail;
+                rdp->curlist = NULL;
+                rdp->curtail = &rdp->curlist;
+        }
+
+        local_irq_disable();
+        if (rdp->nxtlist && !rdp->curlist) {
+                rdp->curlist = rdp->nxtlist;
+                rdp->curtail = rdp->nxttail;
+                rdp->nxtlist = NULL;
+                rdp->nxttail = &rdp->nxtlist;
+                local_irq_enable();
+
+                /*
+                 * start the next batch of callbacks
+                 */
+
+                /* determine batch number */
+                rdp->batch = rcp->cur + 1;
+                /* see the comment and corresponding wmb() in
+                 * the rcu_start_batch()
+                 */
+                smp_rmb();
+
+                if (!rcp->next_pending) {
+                        /* and start it/schedule start if it's a new batch */
+                        spin_lock(&rsp->lock);
+                        rcu_start_batch(rcp, rsp, 1);
+                        spin_unlock(&rsp->lock);
+                }
+        } else {
+                local_irq_enable();
+        }
+        rcu_check_quiescent_state(rcp, rsp, rdp);
+        if (rdp->donelist)
+                rcu_do_batch(rdp);
+}
+
+static void rcu_process_callbacks(unsigned long unused)
+{
+        __rcu_process_callbacks(&rcu_ctrlblk, &rcu_state,
+                                &__get_cpu_var(rcu_data));
+        __rcu_process_callbacks(&rcu_bh_ctrlblk, &rcu_bh_state,
+                                &__get_cpu_var(rcu_bh_data));
+}
+
+void rcu_check_callbacks(int cpu, int user)
+{
+        if (user || 
+            (idle_cpu(cpu) && !in_softirq() && 
+                                hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+                rcu_qsctr_inc(cpu);
+                rcu_bh_qsctr_inc(cpu);
+        } else if (!in_softirq())
+                rcu_bh_qsctr_inc(cpu);
+        tasklet_schedule(&per_cpu(rcu_tasklet, cpu));
+}
+
+static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
+                                                struct rcu_data *rdp)
+{
+        memset(rdp, 0, sizeof(*rdp));
+        rdp->curtail = &rdp->curlist;
+        rdp->nxttail = &rdp->nxtlist;
+        rdp->donetail = &rdp->donelist;
+        rdp->quiescbatch = rcp->completed;
+        rdp->qs_pending = 0;
+        rdp->cpu = cpu;
+}
+
+static void __devinit rcu_online_cpu(int cpu)
+{
+        struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+        struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu);
+
+        rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
+        rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp);
+        tasklet_init(&per_cpu(rcu_tasklet, cpu), rcu_process_callbacks, 0UL);
+}
+
+static int __devinit rcu_cpu_notify(struct notifier_block *self, 
+                                unsigned long action, void *hcpu)
+{
+        long cpu = (long)hcpu;
+        switch (action) {
+        case CPU_UP_PREPARE:
+                rcu_online_cpu(cpu);
+                break;
+        case CPU_DEAD:
+                rcu_offline_cpu(cpu);
+                break;
+        default:
+                break;
+        }
+        return NOTIFY_OK;
+}
+
+static struct notifier_block __devinitdata rcu_nb = {
+        .notifier_call  = rcu_cpu_notify,
+};
+
+/*
+ * Initializes rcu mechanism.  Assumed to be called early.
+ * That is before local timer(SMP) or jiffie timer (uniproc) is setup.
+ * Note that rcu_qsctr and friends are implicitly
+ * initialized due to the choice of ``0'' for RCU_CTR_INVALID.
+ */
+void __init rcu_init(void)
+{
+        rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,
+                        (void *)(long)smp_processor_id());
+        /* Register notifier for non-boot CPUs */
+        register_cpu_notifier(&rcu_nb);
+}
+
+struct rcu_synchronize {
+        struct rcu_head head;
+        struct completion completion;
+};
+
+/* Because of FASTCALL declaration of complete, we use this wrapper */
+static void wakeme_after_rcu(struct rcu_head  *head)
+{
+        struct rcu_synchronize *rcu;
+
+        rcu = container_of(head, struct rcu_synchronize, head);
+        complete(&rcu->completion);
+}
+
+/**
+ * synchronize_kernel - wait until a grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full grace
+ * period has elapsed, in other words after all currently executing RCU
+ * read-side critical sections have completed.  RCU read-side critical
+ * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
+ * and may be nested.
+ */
+void synchronize_kernel(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);
+}
+
+module_param(maxbatch, int, 0);
+EXPORT_SYMBOL_GPL(call_rcu);
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+EXPORT_SYMBOL_GPL(synchronize_kernel);