--- /dev/null
+/*
+ * 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
+ *
+ * Author: Dipankar Sarma <dipankar@in.ibm.com>
+ *
+ * Based on the original work by Paul McKenney <paul.mckenney@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
+ *
+ */
+
+#ifndef __LINUX_RCUPDATE_H
+#define __LINUX_RCUPDATE_H
+
+#ifdef __KERNEL__
+
+#include <linux/cache.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/threads.h>
+
+/**
+ * struct rcu_head - callback structure for use with RCU
+ * @list: list_head to queue the update requests
+ * @func: actual update function to call after the grace period.
+ * @arg: argument to be passed to the actual update function.
+ */
+struct rcu_head {
+ struct list_head list;
+ void (*func)(void *obj);
+ void *arg;
+};
+
+#define RCU_HEAD_INIT(head) \
+ { list: LIST_HEAD_INIT(head.list), func: NULL, arg: NULL }
+#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head)
+#define INIT_RCU_HEAD(ptr) do { \
+ INIT_LIST_HEAD(&(ptr)->list); (ptr)->func = NULL; (ptr)->arg = NULL; \
+} while (0)
+
+
+
+/* Control variables for rcupdate callback mechanism. */
+struct rcu_ctrlblk {
+ spinlock_t mutex; /* Guard this struct */
+ long curbatch; /* Current batch number. */
+ long maxbatch; /* Max requested batch number. */
+ unsigned long rcu_cpu_mask; /* CPUs that need to switch in order */
+ /* for current batch to proceed. */
+};
+
+/* Is batch a before batch b ? */
+static inline int rcu_batch_before(long a, long b)
+{
+ return (a - b) < 0;
+}
+
+/* Is batch a after batch b ? */
+static inline int rcu_batch_after(long a, long b)
+{
+ return (a - b) > 0;
+}
+
+/*
+ * Per-CPU data for Read-Copy UPdate.
+ * nxtlist - new callbacks are added here
+ * curlist - current batch for which quiescent cycle started if any
+ */
+struct rcu_data {
+ long qsctr; /* User-mode/idle loop etc. */
+ long last_qsctr; /* value of qsctr at beginning */
+ /* of rcu grace period */
+ long batch; /* Batch # for current RCU batch */
+ struct list_head nxtlist;
+ struct list_head curlist;
+} ____cacheline_aligned_in_smp;
+
+extern struct rcu_data rcu_data[NR_CPUS];
+extern struct rcu_ctrlblk rcu_ctrlblk;
+
+#define RCU_qsctr(cpu) (rcu_data[(cpu)].qsctr)
+#define RCU_last_qsctr(cpu) (rcu_data[(cpu)].last_qsctr)
+#define RCU_batch(cpu) (rcu_data[(cpu)].batch)
+#define RCU_nxtlist(cpu) (rcu_data[(cpu)].nxtlist)
+#define RCU_curlist(cpu) (rcu_data[(cpu)].curlist)
+
+#define RCU_QSCTR_INVALID 0
+
+static inline int rcu_pending(int cpu)
+{
+ if ((!list_empty(&RCU_curlist(cpu)) &&
+ rcu_batch_before(RCU_batch(cpu), rcu_ctrlblk.curbatch)) ||
+ (list_empty(&RCU_curlist(cpu)) &&
+ !list_empty(&RCU_nxtlist(cpu))) ||
+ test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask))
+ return 1;
+ else
+ return 0;
+}
+
+#define rcu_read_lock() preempt_disable()
+#define rcu_read_unlock() preempt_enable()
+
+extern void rcu_init(void);
+extern void rcu_check_callbacks(int cpu, int user);
+
+/* Exported interfaces */
+extern void FASTCALL(call_rcu(struct rcu_head *head,
+ void (*func)(void *arg), void *arg));
+extern void synchronize_kernel(void);
+
+#endif /* __KERNEL__ */
+#endif /* __LINUX_RCUPDATE_H */
--- /dev/null
+/*
+ * 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
+ *
+ * Author: Dipankar Sarma <dipankar@in.ibm.com>
+ *
+ * Based on the original work by Paul McKenney <paul.mckenney@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 <asm/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/percpu.h>
+#include <linux/rcupdate.h>
+
+/* Definition for rcupdate control block. */
+struct rcu_ctrlblk rcu_ctrlblk =
+ { .mutex = SPIN_LOCK_UNLOCKED, .curbatch = 1,
+ .maxbatch = 1, .rcu_cpu_mask = 0 };
+struct rcu_data rcu_data[NR_CPUS] __cacheline_aligned;
+
+/* Fake initialization required by compiler */
+static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
+#define RCU_tasklet(cpu) (per_cpu(rcu_tasklet, cpu))
+
+/**
+ * call_rcu - Queue an RCU update request.
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual update function to be invoked after the grace period
+ * @arg: argument to be passed to the update function
+ *
+ * The update function will be invoked as soon as all CPUs have performed
+ * a context switch or been seen in the idle loop or in a user process.
+ * The read-side of critical section that use call_rcu() for updation must
+ * be protected by rcu_read_lock()/rcu_read_unlock().
+ */
+void call_rcu(struct rcu_head *head, void (*func)(void *arg), void *arg)
+{
+ int cpu;
+ unsigned long flags;
+
+ head->func = func;
+ head->arg = arg;
+ local_irq_save(flags);
+ cpu = smp_processor_id();
+ list_add_tail(&head->list, &RCU_nxtlist(cpu));
+ 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 list_head *list)
+{
+ struct list_head *entry;
+ struct rcu_head *head;
+
+ while (!list_empty(list)) {
+ entry = list->next;
+ list_del(entry);
+ head = list_entry(entry, struct rcu_head, list);
+ head->func(head->arg);
+ }
+}
+
+/*
+ * 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 the rcu_ctrlblk lock.
+ */
+static void rcu_start_batch(long newbatch)
+{
+ if (rcu_batch_before(rcu_ctrlblk.maxbatch, newbatch)) {
+ rcu_ctrlblk.maxbatch = newbatch;
+ }
+ if (rcu_batch_before(rcu_ctrlblk.maxbatch, rcu_ctrlblk.curbatch) ||
+ (rcu_ctrlblk.rcu_cpu_mask != 0)) {
+ return;
+ }
+ rcu_ctrlblk.rcu_cpu_mask = cpu_online_map;
+}
+
+/*
+ * 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(void)
+{
+ int cpu = smp_processor_id();
+
+ if (!test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask)) {
+ return;
+ }
+
+ /*
+ * Races with local timer interrupt - in the worst case
+ * we may miss one quiescent state of that CPU. That is
+ * tolerable. So no need to disable interrupts.
+ */
+ if (RCU_last_qsctr(cpu) == RCU_QSCTR_INVALID) {
+ RCU_last_qsctr(cpu) = RCU_qsctr(cpu);
+ return;
+ }
+ if (RCU_qsctr(cpu) == RCU_last_qsctr(cpu)) {
+ return;
+ }
+
+ spin_lock(&rcu_ctrlblk.mutex);
+ if (!test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask)) {
+ spin_unlock(&rcu_ctrlblk.mutex);
+ return;
+ }
+ clear_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask);
+ RCU_last_qsctr(cpu) = RCU_QSCTR_INVALID;
+ if (rcu_ctrlblk.rcu_cpu_mask != 0) {
+ spin_unlock(&rcu_ctrlblk.mutex);
+ return;
+ }
+ rcu_ctrlblk.curbatch++;
+ rcu_start_batch(rcu_ctrlblk.maxbatch);
+ spin_unlock(&rcu_ctrlblk.mutex);
+}
+
+
+/*
+ * This does the RCU processing work from tasklet context.
+ */
+static void rcu_process_callbacks(unsigned long unused)
+{
+ int cpu = smp_processor_id();
+ LIST_HEAD(list);
+
+ if (!list_empty(&RCU_curlist(cpu)) &&
+ rcu_batch_after(rcu_ctrlblk.curbatch, RCU_batch(cpu))) {
+ list_splice(&RCU_curlist(cpu), &list);
+ INIT_LIST_HEAD(&RCU_curlist(cpu));
+ }
+
+ local_irq_disable();
+ if (!list_empty(&RCU_nxtlist(cpu)) && list_empty(&RCU_curlist(cpu))) {
+ list_splice(&RCU_nxtlist(cpu), &RCU_curlist(cpu));
+ INIT_LIST_HEAD(&RCU_nxtlist(cpu));
+ local_irq_enable();
+
+ /*
+ * start the next batch of callbacks
+ */
+ spin_lock(&rcu_ctrlblk.mutex);
+ RCU_batch(cpu) = rcu_ctrlblk.curbatch + 1;
+ rcu_start_batch(RCU_batch(cpu));
+ spin_unlock(&rcu_ctrlblk.mutex);
+ } else {
+ local_irq_enable();
+ }
+ rcu_check_quiescent_state();
+ if (!list_empty(&list))
+ rcu_do_batch(&list);
+}
+
+void rcu_check_callbacks(int cpu, int user)
+{
+ if (user ||
+ (idle_cpu(cpu) && !in_softirq() && hardirq_count() <= 1))
+ RCU_qsctr(cpu)++;
+ tasklet_schedule(&RCU_tasklet(cpu));
+}
+
+/*
+ * 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)
+{
+ int i;
+
+ memset(&rcu_data[0], 0, sizeof(rcu_data));
+ for (i = 0; i < NR_CPUS; i++) {
+ tasklet_init(&RCU_tasklet(i), rcu_process_callbacks, 0UL);
+ INIT_LIST_HEAD(&RCU_nxtlist(i));
+ INIT_LIST_HEAD(&RCU_curlist(i));
+ }
+}
+
+/* Because of FASTCALL declaration of complete, we use this wrapper */
+static void wakeme_after_rcu(void *completion)
+{
+ complete(completion);
+}
+
+/**
+ * synchronize-kernel - wait until all the CPUs have gone
+ * through a "quiescent" state. It may sleep.
+ */
+void synchronize_kernel(void)
+{
+ struct rcu_head rcu;
+ DECLARE_COMPLETION(completion);
+
+ /* Will wake me after RCU finished */
+ call_rcu(&rcu, wakeme_after_rcu, &completion);
+
+ /* Wait for it */
+ wait_for_completion(&completion);
+}
+
+
+EXPORT_SYMBOL(call_rcu);
+EXPORT_SYMBOL(synchronize_kernel);
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