rcu: Move RCU-related source code to kernel/rcu directory

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 388 insertions, 0 deletions

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
new file mode 100644
index 00000000000..0c9a934cfec
--- /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);
+}