forward port jRCU to 3.2

Index: 3.2/kernel/jrcu.c
===================================================================
@@ -0,0 +1,786 @@
+/*
+ * Joe's tiny RCU, for small SMP systems.
+ *
+ * The main purpose of jRCU is to bring together and execute on a single
+ * CPU the RCU end-of-batch operations of all CPUs.  This relieves all but
+ * one CPU from this periodic responsibility. This is important when the
+ * system has user supplied realtime applications that require the full
+ * use of CPUs dedicated to those applications.
+ *
+ * A secondary purpose is to come up with an RCU implementation that is as
+ * simple as possible yet still suitable for SMP platforms, at least the
+ * smaller ones.  In this regard it fills the gap between TinyRCU, which
+ * runs on uniprocessors only, and TreeRCU, a deeply complex implementation
+ * best suited for the largest NUMA boxes on Earth.
+ *
+ * Algorithm: jRCU is frame based.  That is, it periodically wakes up and
+ * either advances jRCU state or it NOPs.  For state to advance, every CPU
+ * must have at least one period, however small, where its preempt_count()
+ * is zero, since the last time jRCU state advanced.
+ *
+ * 'Advancing state' simply means moving the functions queued up by
+ * call_rcu() along a FIFO.  Those that drop off the end of the FIFO are
+ * invoked before being discarded.  jRCU advances batches of functions
+ * through the FIFO rather than individual functions; when a function is
+ * queued, call_rcu() puts it into the batch that is at the head of the FIFO.
+ *
+ * jRCU assumes that the frames are large enough that architecture barrier
+ * operations performed in one frame have fully completed by the start of
+ * the next.  This period is presumed to be in the tens of microseconds, so
+ * it may not be wise to run jRCU at a frame rate under 100 usecs.
+ *
+ * Author: Joe Korty <[email protected]>
+ *
+ * Acknowledgements: Paul E. McKenney's 'TinyRCU for uniprocessors' inspired
+ * the thought that there could could be something similiarly simple for SMP.
+ * The rcu_list chain operators are from Jim Houston's Alternative RCU.
+ *
+ * Copyright Concurrent Computer Corporation, 2011
+ *
+ * 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.
+ */
+
+/*
+ * This RCU maintains three callback lists: the current batch (per cpu),
+ * the previous batch (also per cpu), and the pending list (global).
+ */
+
+#include <linux/bug.h>
+#include <linux/smp.h>
+#include <linux/ctype.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/stddef.h>
+#include <linux/string.h>
+#include <linux/preempt.h>
+#include <linux/uaccess.h>
+#include <linux/compiler.h>
+#include <linux/irqflags.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+
+#include <asm/system.h>
+
+/*
+ * Define an rcu list type and operators.  An rcu list has only ->next
+ * pointers for the chain nodes; the list head however is special and
+ * has pointers to both the first and last nodes of the chain.  Tweaked
+ * so that null head, tail pointers can be used to signify an empty list.
+ */
+struct rcu_list {
+	struct rcu_head *head;
+	struct rcu_head **tail;
+	int count;		/* stats-n-debug */
+};
+
+static inline void rcu_list_init(struct rcu_list *l)
+{
+	l->head = NULL;
+	l->tail = NULL;
+	l->count = 0;
+}
+
+/*
+ * Add an element to the tail of an rcu list
+ */
+static inline void rcu_list_add(struct rcu_list *l, struct rcu_head *h)
+{
+	if (unlikely(l->tail == NULL))
+		l->tail = &l->head;
+	*l->tail = h;
+	l->tail = &h->next;
+	l->count++;
+	h->next = NULL;
+}
+
+/*
+ * Append the contents of one rcu list to another.  The 'from' list is left
+ * corrupted on exit; the caller must re-initialize it before it can be used
+ * again.
+ */
+static inline void rcu_list_join(struct rcu_list *to, struct rcu_list *from)
+{
+	if (from->head) {
+		if (unlikely(to->tail == NULL)) {
+			to->tail = &to->head;
+			to->count = 0;
+		}
+		*to->tail = from->head;
+		to->tail = from->tail;
+		to->count += from->count;
+	}
+}
+
+/*
+ * selects, in ->cblist[] below, which is the current callback list and which
+ * is the previous.
+ */
+static u8 rcu_which ____cacheline_aligned_in_smp;
+
+struct rcu_data {
+	u8 wait;		/* goes false when this cpu consents to
+				 * the retirement of the current batch */
+	struct rcu_list cblist[2]; /* current & previous callback lists */
+	s64 nqueued;		/* #callbacks queued (stats-n-debug) */
+} ____cacheline_aligned_in_smp;
+
+static struct rcu_data rcu_data[NR_CPUS];
+
+/* debug & statistics stuff */
+static struct rcu_stats {
+	unsigned npasses;	/* #passes made */
+	unsigned nlast;		/* #passes since last end-of-batch */
+	unsigned nbatches;	/* #end-of-batches (eobs) seen */
+	unsigned nmis;		/* #passes discarded due to NMI */
+	atomic_t nbarriers;	/* #rcu barriers processed */
+	atomic_t nsyncs;	/* #rcu syncs processed */
+	s64 ninvoked;		/* #invoked (ie, finished) callbacks */
+	unsigned nforced;	/* #forced eobs (should be zero) */
+} rcu_stats;
+
+#define RCU_HZ			(20)
+#define RCU_HZ_PERIOD_US	(USEC_PER_SEC / RCU_HZ)
+#define RCU_HZ_DELTA_US		(USEC_PER_SEC / HZ)
+
+static int rcu_hz_period_us = RCU_HZ_PERIOD_US;
+static int rcu_hz_delta_us = RCU_HZ_DELTA_US;
+
+static int rcu_hz_precise;
+
+int rcu_scheduler_active __read_mostly;
+int rcu_nmi_seen __read_mostly;
+
+static int rcu_wdog_ctr;	/* time since last end-of-batch, in usecs */
+static int rcu_wdog_lim = 10 * USEC_PER_SEC;	/* rcu watchdog interval */
+
+/*
+ * Return our CPU id or zero if we are too early in the boot process to
+ * know what that is.  For RCU to work correctly, a cpu named '0' must
+ * eventually be present (but need not ever be online).
+ */
+#ifdef HAVE_THREAD_INFO_CPU
+static inline int rcu_cpu(void)
+{
+	return current_thread_info()->cpu;
+}
+
+#else
+
+static unsigned rcu_cpu_early_flag __read_mostly = 1;
+
+static inline int rcu_cpu(void)
+{
+	if (unlikely(rcu_cpu_early_flag)) {
+		if (!(rcu_scheduler_active && nr_cpu_ids > 1))
+			return 0;
+		rcu_cpu_early_flag = 0;
+	}
+	return raw_smp_processor_id();
+}
+#endif /* HAVE_THREAD_INFO_CPU */
+
+/*
+ * Invoke whenever the calling CPU consents to end-of-batch.  All CPUs
+ * must so consent before the batch is truly ended.
+ */
+static inline void rcu_eob(int cpu)
+{
+	struct rcu_data *rd = &rcu_data[cpu];
+	if (unlikely(rd->wait)) {
+		rd->wait = 0;
+#ifndef CONFIG_JRCU_LAZY
+		smp_mb();
+#endif
+	}
+}
+
+void jrcu_read_unlock(void)
+{
+	if (preempt_count() == 1)
+		rcu_eob(rcu_cpu());
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(jrcu_read_unlock);
+
+void rcu_note_context_switch(int cpu)
+{
+	rcu_eob(cpu);
+}
+EXPORT_SYMBOL_GPL(rcu_note_context_switch);
+
+void rcu_note_might_resched(void)
+{
+	unsigned long flags;
+
+	raw_local_irq_save(flags);
+	rcu_eob(rcu_cpu());
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL(rcu_note_might_resched);
+
+struct rcu_synchronize {
+	struct rcu_head head;
+	struct completion completion;
+};
+
+static void wakeme_after_rcu(struct rcu_head  *head)
+{
+	struct rcu_synchronize *rcu;
+
+	rcu = container_of(head, struct rcu_synchronize, head);
+	complete(&rcu->completion);
+}
+
+void synchronize_sched(void)
+{
+	struct rcu_synchronize rcu;
+
+	if (!rcu_scheduler_active)
+		return;
+
+	init_completion(&rcu.completion);
+	call_rcu(&rcu.head, wakeme_after_rcu);
+	wait_for_completion(&rcu.completion);
+	atomic_inc(&rcu_stats.nsyncs);
+
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+void rcu_barrier(void)
+{
+	synchronize_sched();
+	synchronize_sched();
+	atomic_inc(&rcu_stats.nbarriers);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+void rcu_force_quiescent_state(void)
+{
+}
+EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
+
+
+/*
+ * Insert an RCU callback onto the calling CPUs list of 'current batch'
+ * callbacks.  Lockless version, can be invoked anywhere except under NMI.
+ */
+void call_rcu_sched(struct rcu_head *cb, void (*func)(struct rcu_head *rcu))
+{
+	unsigned long flags;
+	struct rcu_data *rd;
+	struct rcu_list *cblist;
+	int which;
+
+	cb->func = func;
+	cb->next = NULL;
+
+	raw_local_irq_save(flags);
+	smp_mb();
+
+	rd = &rcu_data[rcu_cpu()];
+	which = ACCESS_ONCE(rcu_which);
+	cblist = &rd->cblist[which];
+
+	/* The following is not NMI-safe, therefore call_rcu()
+	 * cannot be invoked under NMI. */
+	rcu_list_add(cblist, cb);
+	rd->nqueued++;
+	smp_mb();
+	raw_local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(call_rcu_sched);
+
+/*
+ * Invoke all callbacks on the passed-in list.
+ */
+static void rcu_invoke_callbacks(struct rcu_list *pending)
+{
+	struct rcu_head *curr, *next;
+
+	for (curr = pending->head; curr;) {
+		unsigned long offset = (unsigned long)curr->func;
+		next = curr->next;
+		if (__is_kfree_rcu_offset(offset))
+			kfree((void *)curr - offset);
+		else
+			curr->func(curr);
+		curr = next;
+		rcu_stats.ninvoked++;
+	}
+}
+
+/*
+ * Check if the conditions for ending the current batch are true. If
+ * so then end it.
+ *
+ * Must be invoked periodically, and the periodic invocations must be
+ * far enough apart in time for the previous batch to become quiescent.
+ * This is a few tens of microseconds unless NMIs are involved; an NMI
+ * stretches out the requirement by the duration of the NMI.
+ *
+ * "Quiescent" means the owning cpu is no longer appending callbacks
+ * and has completed execution of a trailing write-memory-barrier insn.
+ */
+static void __rcu_delimit_batches(struct rcu_list *pending)
+{
+	struct rcu_data *rd;
+	struct rcu_list *plist;
+	int cpu, eob, prev;
+
+	if (!rcu_scheduler_active)
+		return;
+
+	rcu_stats.nlast++;
+
+	/* If an NMI occured then the previous batch may not yet be
+	 * quiescent.  Let's wait till it is.
+	 */
+	if (rcu_nmi_seen) {
+		rcu_nmi_seen = 0;
+		rcu_stats.nmis++;
+		return;
+	}
+
+	/*
+	 * Find out if the current batch has ended
+	 * (end-of-batch).
+	 */
+	eob = 1;
+	for_each_online_cpu(cpu) {
+		rd = &rcu_data[cpu];
+		if (rd->wait) {
+			rd->wait = preempt_count_cpu(cpu) > idle_cpu(cpu);
+			if (rd->wait) {
+				eob = 0;
+				break;
+			}
+		}
+	}
+
+	/*
+	 * Exit if batch has not ended.  But first, tickle all non-cooperating
+	 * CPUs if enough time has passed.
+	 */
+	if (eob == 0) {
+		if (rcu_wdog_ctr >= rcu_wdog_lim) {
+			rcu_wdog_ctr = 0;
+			rcu_stats.nforced++;
+			for_each_online_cpu(cpu) {
+				if (rcu_data[cpu].wait)
+					force_cpu_resched(cpu);
+			}
+		}
+		rcu_wdog_ctr += rcu_hz_period_us;
+		return;
+	}
+
+	/*
+	 * End the current RCU batch and start a new one.
+	 *
+	 * This is a two-step operation: move every cpu's previous list
+	 * to the global pending list, then tell every cpu to swap its
+	 * current and pending lists (ie, toggle rcu_which).
+	 *
+	 * We tolerate the cpus taking a bit of time noticing this swap;
+	 * we expect them to continue to put callbacks on the old current
+	 * list (which is now the previous list) for a while.  That time,
+	 * however, cannot exceed one RCU_HZ period.
+	 */
+	prev = ACCESS_ONCE(rcu_which) ^ 1;
+
+	for_each_present_cpu(cpu) {
+		rd = &rcu_data[cpu];
+		plist = &rd->cblist[prev];
+		/* Chain previous batch of callbacks, if any, to the pending list */
+		if (plist->head) {
+			rcu_list_join(pending, plist);
+			rcu_list_init(plist);
+		}
+		if (cpu_online(cpu)) /* wins race with offlining every time */
+			rd->wait = preempt_count_cpu(cpu) > idle_cpu(cpu);
+		else
+			rd->wait = 0;
+	}
+	smp_mb(); /* just paranoia, the below xchg should do this on all archs */
+
+	/*
+	 * Swap current and previous lists.  The other cpus must not
+	 * see this out-of-order w.r.t. the above emptying of each cpu's
+	 * previous list.  The xchg accomplishes that and, as a side (but
+	 * seemingly unneeded) bonus, keeps this cpu from advancing its insn
+	 * counter until the results of that xchg are visible on other cpus.
+	 */
+	xchg(&rcu_which, prev); /* only place where rcu_which is written to */
+
+	rcu_stats.nbatches++;
+	rcu_stats.nlast = 0;
+	rcu_wdog_ctr = 0;
+}
+
+static void rcu_delimit_batches(void)
+{
+	unsigned long flags;
+	struct rcu_list pending;
+
+	rcu_list_init(&pending);
+	rcu_stats.npasses++;
+
+	raw_local_irq_save(flags);
+	smp_mb();
+	__rcu_delimit_batches(&pending);
+	smp_mb();
+	raw_local_irq_restore(flags);
+
+	if (pending.head)
+		rcu_invoke_callbacks(&pending);
+}
+
+/* ------------------ interrupt driver section ------------------ */
+
+/*
+ * We drive RCU from a periodic interrupt during most of boot. Once boot
+ * is complete we (optionally) transition to a daemon.
+ */
+
+#include <linux/time.h>
+#include <linux/delay.h>
+#include <linux/hrtimer.h>
+#include <linux/interrupt.h>
+
+#define rcu_hz_period_ns	(rcu_hz_period_us * NSEC_PER_USEC)
+#define rcu_hz_delta_ns		(rcu_hz_delta_us * NSEC_PER_USEC)
+
+static struct hrtimer rcu_timer;
+
+static void rcu_softirq_func(struct softirq_action *h)
+{
+	rcu_delimit_batches();
+}
+
+static enum hrtimer_restart rcu_timer_func(struct hrtimer *t)
+{
+	ktime_t next;
+
+	raise_softirq(RCU_SOFTIRQ);
+
+	next = ktime_add_ns(ktime_get(), rcu_hz_period_ns);
+	hrtimer_set_expires_range_ns(&rcu_timer, next,
+		rcu_hz_precise ? 0 : rcu_hz_delta_ns);
+	return HRTIMER_RESTART;
+}
+
+static void rcu_timer_start(void)
+{
+	hrtimer_forward_now(&rcu_timer, ns_to_ktime(rcu_hz_period_ns));
+	hrtimer_start_expires(&rcu_timer, HRTIMER_MODE_ABS);
+}
+
+static __init void rcu_timer_init(void)
+{
+	open_softirq(RCU_SOFTIRQ, rcu_softirq_func);
+
+	hrtimer_init(&rcu_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	rcu_timer.function = rcu_timer_func;
+}
+
+#ifdef CONFIG_JRCU_DAEMON
+static void rcu_timer_stop(void)
+{
+	hrtimer_cancel(&rcu_timer);
+}
+#endif
+
+void __init rcu_scheduler_starting(void)
+{
+	rcu_timer_init();
+}
+
+#ifndef CONFIG_JRCU_DAEMON
+
+void __init int rcu_start_callback_processing(void)
+{
+	rcu_timer_start();
+	rcu_scheduler_active = 1;
+
+	pr_info("JRCU: callback processing via timer has started.\n");
+	return 0;
+}
+
+#else /* CONFIG_JRCU_DAEMON */
+
+/* ------------------ daemon driver section --------------------- */
+
+/*
+ * Once the system is fully up, we will drive the periodic-polling part
+ * of JRCU from a kernel daemon, jrcud.  Until then it is driven by
+ * an interrupt.
+ */
+#include <linux/err.h>
+#include <linux/param.h>
+#include <linux/kthread.h>
+
+static int rcu_priority;
+static struct task_struct *rcu_daemon;
+
+static int jrcu_set_priority(int priority)
+{
+	struct sched_param param;
+
+	if (priority == 0) {
+		set_user_nice(current, -19);
+		return 0;
+	}
+
+	if (priority < 0)
+		param.sched_priority = MAX_USER_RT_PRIO + priority;
+	else
+		param.sched_priority = priority;
+
+	sched_setscheduler_nocheck(current, SCHED_RR, &param);
+	return param.sched_priority;
+}
+
+static int jrcud_func(void *arg)
+{
+	current->flags |= PF_NOFREEZE;
+	rcu_priority = jrcu_set_priority(CONFIG_JRCU_DAEMON_PRIO);
+	rcu_timer_stop();
+
+	pr_info("JRCU: callback processing via daemon started.\n");
+
+	while (!kthread_should_stop()) {
+		if (rcu_hz_precise) {
+			usleep_range(rcu_hz_period_us,
+				rcu_hz_period_us);
+		} else {
+			usleep_range(rcu_hz_period_us,
+				rcu_hz_period_us + rcu_hz_delta_us);
+		}
+		rcu_delimit_batches();
+	}
+
+	pr_info("JRCU: replaced callback daemon with a timer.\n");
+
+	rcu_daemon = NULL;
+	rcu_timer_start();
+	return 0;
+}
+
+static __init int rcu_start_callback_processing(void)
+{
+	struct task_struct *p;
+
+	p = kthread_run(jrcud_func, NULL, "jrcud");
+	if (IS_ERR(p)) {
+		pr_warn("JRCU: cannot replace callback timer with a daemon\n");
+		return -ENODEV;
+	}
+	rcu_daemon = p;
+	rcu_scheduler_active = 1;
+
+	pr_info("JRCU: callback processing now allowed.\n");
+	return 0;
+}
+
+#endif /* CONFIG_JRCU_DAEMON */
+
+subsys_initcall_sync(rcu_start_callback_processing);
+
+/* ------------------ debug and statistics section -------------- */
+
+#ifdef CONFIG_DEBUG_FS
+
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+static int rcu_hz = RCU_HZ;
+
+static int rcu_debugfs_show(struct seq_file *m, void *unused)
+{
+	int cpu, q;
+	s64 nqueued;
+
+	nqueued = 0;
+	for_each_present_cpu(cpu)
+		nqueued += rcu_data[cpu].nqueued;
+
+	seq_printf(m, "%14u: hz, %s\n",
+		rcu_hz,
+		rcu_hz_precise ? "precise" : "sloppy");
+
+	seq_printf(m, "%14u: watchdog (secs)\n", rcu_wdog_lim / (int)USEC_PER_SEC);
+	seq_printf(m, "%14d: #secs left on watchdog\n",
+		(rcu_wdog_lim - rcu_wdog_ctr) / (int)USEC_PER_SEC);
+
+#ifdef CONFIG_JRCU_DAEMON
+	if (rcu_daemon)
+		seq_printf(m, "%14u: daemon priority\n", rcu_priority);
+	else
+		seq_printf(m, "%14s: daemon priority\n", "none, no daemon");
+#endif
+
+	seq_printf(m, "\n");
+	seq_printf(m, "%14u: #passes\n",
+		rcu_stats.npasses);
+	seq_printf(m, "%14u: #passes discarded due to NMI\n",
+		rcu_stats.nmis);
+	seq_printf(m, "%14u: #passes resulting in end-of-batch\n",
+		rcu_stats.nbatches);
+	seq_printf(m, "%14u: #passes not resulting in end-of-batch\n",
+		rcu_stats.npasses - rcu_stats.nbatches);
+	seq_printf(m, "%14u: #passes since last end-of-batch\n",
+		rcu_stats.nlast);
+	seq_printf(m, "%14u: #passes forced (0 is best)\n",
+		rcu_stats.nforced);
+
+	seq_printf(m, "\n");
+	seq_printf(m, "%14u: #barriers\n",
+		atomic_read(&rcu_stats.nbarriers));
+	seq_printf(m, "%14u: #syncs\n",
+		atomic_read(&rcu_stats.nsyncs));
+	seq_printf(m, "%14llu: #callbacks invoked\n",
+		rcu_stats.ninvoked);
+	seq_printf(m, "%14d: #callbacks left to invoke\n",
+		(int)(nqueued - rcu_stats.ninvoked));
+	seq_printf(m, "\n");
+
+	for_each_online_cpu(cpu)
+		seq_printf(m, "%4d ", cpu);
+	seq_printf(m, "  CPU\n");
+
+	for_each_online_cpu(cpu) {
+		struct rcu_data *rd = &rcu_data[cpu];
+		seq_printf(m, "--%c%c ",
+			idle_cpu(cpu) ? 'I' : '-',
+			rd->wait ? 'W' : '-');
+	}
+	seq_printf(m, "  FLAGS\n");
+
+	for (q = 0; q < 2; q++) {
+		int w = ACCESS_ONCE(rcu_which);
+		for_each_online_cpu(cpu) {
+			struct rcu_data *rd = &rcu_data[cpu];
+			struct rcu_list *l = &rd->cblist[q];
+			seq_printf(m, "%4d ", l->count);
+		}
+		seq_printf(m, "  Q%d%c\n", q, " *"[q == w]);
+	}
+	seq_printf(m, "\nFLAGS:\n");
+	seq_printf(m, "  I - cpu idle, W - cpu waiting for end-of-batch,\n");
+	seq_printf(m, "  * - the current Q, other is the previous Q.\n");
+
+	return 0;
+}
+
+static ssize_t rcu_debugfs_write(struct file *file,
+	const char __user *buffer, size_t count, loff_t *ppos)
+{
+	int i, j, c;
+	char token[32];
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (count <= 0)
+		return count;
+
+	if (!access_ok(VERIFY_READ, buffer, count))
+		return -EFAULT;
+
+	i = 0;
+	if (__get_user(c, &buffer[i++]))
+		return -EFAULT;
+
+next:
+	/* Token extractor -- first, skip leading whitepace */
+	while (c && isspace(c) && i < count) {
+		if (__get_user(c, &buffer[i++]))
+			return -EFAULT;
+	}
+
+	if (i >= count || c == 0)
+		return count;	/* all done, no more tokens */
+
+	j = 0;
+	do {
+		if (j == (sizeof(token) - 1))
+			return -EINVAL;
+		token[j++] = c;
+		if (__get_user(c, &buffer[i++]))
+			return -EFAULT;
+	} while (c && !isspace(c) && i < count); /* extract next token */
+	token[j++] = 0;
+
+	if (!strncmp(token, "hz=", 3)) {
+		int rcu_hz_wanted = -1;
+		sscanf(&token[3], "%d", &rcu_hz_wanted);
+		if (rcu_hz_wanted < 2 || rcu_hz_wanted > 1000)
+			return -EINVAL;
+		rcu_hz = rcu_hz_wanted;
+		rcu_hz_period_us = USEC_PER_SEC / rcu_hz;
+	} else if (!strncmp(token, "precise=", 8)) {
+		sscanf(&token[8], "%d", &rcu_hz_precise);
+	} else if (!strncmp(token, "wdog=", 5)) {
+		int wdog = -1;
+		sscanf(&token[5], "%d", &wdog);
+		if (wdog < 3 || wdog > 1000)
+			return -EINVAL;
+		rcu_wdog_lim = wdog * USEC_PER_SEC;
+	} else
+		return -EINVAL;
+	goto next;
+}
+
+static int rcu_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, rcu_debugfs_show, NULL);
+}
+
+static const struct file_operations rcu_debugfs_fops = {
+	.owner = THIS_MODULE,
+	.open = rcu_debugfs_open,
+	.read = seq_read,
+	.write = rcu_debugfs_write,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+static struct dentry *rcudir;
+
+static int __init rcu_debugfs_init(void)
+{
+	struct dentry *retval;
+
+	rcudir = debugfs_create_dir("rcu", NULL);
+	if (!rcudir)
+		goto error;
+
+	retval = debugfs_create_file("rcudata", 0644, rcudir,
+			NULL, &rcu_debugfs_fops);
+	if (!retval)
+		goto error;
+
+	return 0;
+
+error:
+	debugfs_remove_recursive(rcudir);
+	pr_warn("JRCU: Could not create debugfs files.\n");
+	return -ENOSYS;
+}
+late_initcall(rcu_debugfs_init);
+#endif /* CONFIG_DEBUG_FS */

80 lines not on this page · raw message

Index: 3.2/include/linux/rcupdate.h
===================================================================
@@ -208,6 +208,8 @@
 #include <linux/rcutree.h>
 #elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
 #include <linux/rcutiny.h>
+#elif defined(CONFIG_JRCU)
+#include <linux/jrcu.h>
 #else
 #error "Unknown RCU implementation specified to kernel configuration"
 #endif

Index: 3.2/include/linux/hardirq.h
===================================================================
@@ -139,7 +139,13 @@
 extern void account_system_vtime(struct task_struct *tsk);
 #endif
 
-#if defined(CONFIG_NO_HZ)
+#if defined(CONFIG_JRCU)
+extern int rcu_nmi_seen;
+# define rcu_irq_enter() do { } while (0)
+# define rcu_irq_exit() do { } while (0)
+# define rcu_nmi_enter() do { rcu_nmi_seen = 1; } while (0)
+# define rcu_nmi_exit() do { } while (0)
+#elif defined(CONFIG_NO_HZ)
 #if defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
 extern void rcu_enter_nohz(void);
 extern void rcu_exit_nohz(void);

85 lines not on this page · raw message

Index: 3.2/include/linux/preempt.h
===================================================================
@@ -10,18 +10,45 @@
 #include <linux/linkage.h>
 #include <linux/list.h>
 
+/* cannot include rcupdate.h here, so open-code this */
+
+#if defined(CONFIG_JRCU)
+# define __add_preempt_count(val) do { \
+	int newval = (preempt_count() += (val)); \
+	if (newval == (val)) \
+		smp_wmb(); \
+} while (0)
+#else
+# define __add_preempt_count(val) do { preempt_count() += (val); } while (0)
+#endif
+
+#if defined(CONFIG_JRCU_LAZY) || !defined(CONFIG_JRCU)
+# define __sub_preempt_count(val) do { preempt_count() -= (val); } while (0)
+#else
+# define __sub_preempt_count(val) do { \
+	int newval = (preempt_count() -= (val)); \
+	if (newval == 0) { \
+		/* race with preemption OK, preempt will do the mb for us */ \
+		smp_wmb(); \
+	} \
+} while (0)
+#endif
+
 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
   extern void add_preempt_count(int val);
   extern void sub_preempt_count(int val);
 #else
-# define add_preempt_count(val)	do { preempt_count() += (val); } while (0)
-# define sub_preempt_count(val)	do { preempt_count() -= (val); } while (0)
+# define add_preempt_count(val) __add_preempt_count(val)
+# define sub_preempt_count(val) __sub_preempt_count(val)
 #endif
 
 #define inc_preempt_count() add_preempt_count(1)
 #define dec_preempt_count() sub_preempt_count(1)
 
 #define preempt_count()	(current_thread_info()->preempt_count)
+#ifdef CONFIG_PREEMPT_COUNT_CPU
+extern int preempt_count_cpu(int cpu);
+#endif
 
 #ifdef CONFIG_PREEMPT
 

Index: 3.2/include/linux/kernel.h
===================================================================
@@ -122,11 +122,18 @@
 struct pt_regs;
 struct user;
 
+/* cannot bring in linux/rcupdate.h at this point */
+#ifdef CONFIG_JRCU
+extern void rcu_note_might_resched(void);
+#else
+#define rcu_note_might_resched()
+#endif /*JRCU */
+
 #ifdef CONFIG_PREEMPT_VOLUNTARY
 extern int _cond_resched(void);
-# define might_resched() _cond_resched()
+# define might_resched() do { _cond_resched(); rcu_note_might_resched(); } while (0)
 #else
-# define might_resched() do { } while (0)
+# define might_resched() do { rcu_note_might_resched(); } while (0)
 #endif
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP

Index: 3.2/arch/x86/include/asm/thread_info.h
===================================================================
@@ -29,6 +29,7 @@
 	__u32			flags;		/* low level flags */
 	__u32			status;		/* thread synchronous flags */
 	__u32			cpu;		/* current CPU */
+#define HAVE_THREAD_INFO_CPU	1
 	int			preempt_count;	/* 0 => preemptable,
 						   <0 => BUG */
 	mm_segment_t		addr_limit;

Index: 3.2/include/linux/sched.h
===================================================================
@@ -1982,6 +1982,8 @@
 static inline void wake_up_idle_cpu(int cpu) { }
 #endif
 
+extern void force_cpu_resched(int cpu);
+
 extern unsigned int sysctl_sched_latency;
 extern unsigned int sysctl_sched_min_granularity;
 extern unsigned int sysctl_sched_wakeup_granularity;