1 files changed, 132 insertions, 123 deletions

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index f8488965250f..585cade21010 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -1,23 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0+
 /*
  * 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, you can access it online at
- * http://www.gnu.org/licenses/gpl-2.0.html.
- *
  * Copyright IBM Corporation, 2008
  *
- * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ * Author: Paul E. McKenney <paulmck@linux.ibm.com>
  *
  * For detailed explanation of Read-Copy Update mechanism see -
  *		Documentation/RCU
@@ -35,6 +22,8 @@
 #include <linux/time.h>
 #include <linux/cpu.h>
 #include <linux/prefetch.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
 
 #include "rcu.h"
 
@@ -43,74 +32,33 @@ struct rcu_ctrlblk {
 	struct rcu_head *rcucblist;	/* List of pending callbacks (CBs). */
 	struct rcu_head **donetail;	/* ->next pointer of last "done" CB. */
 	struct rcu_head **curtail;	/* ->next pointer of last CB. */
+	unsigned long gp_seq;		/* Grace-period counter. */
 };
 
 /* Definition for rcupdate control block. */
-static struct rcu_ctrlblk rcu_sched_ctrlblk = {
-	.donetail	= &rcu_sched_ctrlblk.rcucblist,
-	.curtail	= &rcu_sched_ctrlblk.rcucblist,
-};
-
-static struct rcu_ctrlblk rcu_bh_ctrlblk = {
-	.donetail	= &rcu_bh_ctrlblk.rcucblist,
-	.curtail	= &rcu_bh_ctrlblk.rcucblist,
+static struct rcu_ctrlblk rcu_ctrlblk = {
+	.donetail	= &rcu_ctrlblk.rcucblist,
+	.curtail	= &rcu_ctrlblk.rcucblist,
+	.gp_seq		= 0 - 300UL,
 };
 
-#include "tiny_plugin.h"
-
-void rcu_barrier_bh(void)
+void rcu_barrier(void)
 {
-	wait_rcu_gp(call_rcu_bh);
+	wait_rcu_gp(call_rcu_hurry);
 }
-EXPORT_SYMBOL(rcu_barrier_bh);
+EXPORT_SYMBOL(rcu_barrier);
 
-void rcu_barrier_sched(void)
-{
-	wait_rcu_gp(call_rcu_sched);
-}
-EXPORT_SYMBOL(rcu_barrier_sched);
-
-/*
- * 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)
-{
-	if (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(void)
-{
-	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(void)
+/* Record an rcu quiescent state.  */
+void rcu_qs(void)
 {
 	unsigned long flags;
 
 	local_irq_save(flags);
-	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
-		raise_softirq(RCU_SOFTIRQ);
+	if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) {
+		rcu_ctrlblk.donetail = rcu_ctrlblk.curtail;
+		raise_softirq_irqoff(RCU_SOFTIRQ);
+	}
+	WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2);
 	local_irq_restore(flags);
 }
 
@@ -120,38 +68,52 @@ void rcu_bh_qs(void)
  * be called from hardirq context.  It is normally called from the
  * scheduling-clock interrupt.
  */
-void rcu_check_callbacks(int user)
+void rcu_sched_clock_irq(int user)
 {
 	if (user)
-		rcu_sched_qs();
-	else if (!in_softirq())
-		rcu_bh_qs();
-	if (user)
-		rcu_note_voluntary_context_switch(current);
+		rcu_qs();
+	else if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail)
+		set_need_resched_current();
 }
 
 /*
- * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
- * whose grace period has elapsed.
+ * Reclaim the specified callback, either by invoking it for non-kfree cases or
+ * freeing it directly (for kfree). Return true if kfreeing, false otherwise.
  */
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+static inline bool rcu_reclaim_tiny(struct rcu_head *head)
+{
+	rcu_callback_t f;
+
+	rcu_lock_acquire(&rcu_callback_map);
+
+	trace_rcu_invoke_callback("", head);
+	f = head->func;
+	debug_rcu_head_callback(head);
+	WRITE_ONCE(head->func, (rcu_callback_t)0L);
+	f(head);
+	rcu_lock_release(&rcu_callback_map);
+	return false;
+}
+
+/* Invoke the RCU callbacks whose grace period has elapsed.  */
+static __latent_entropy void rcu_process_callbacks(void)
 {
 	struct rcu_head *next, *list;
 	unsigned long flags;
 
 	/* Move the ready-to-invoke callbacks to a local list. */
 	local_irq_save(flags);
-	if (rcp->donetail == &rcp->rcucblist) {
+	if (rcu_ctrlblk.donetail == &rcu_ctrlblk.rcucblist) {
 		/* No callbacks ready, so just leave. */
 		local_irq_restore(flags);
 		return;
 	}
-	list = rcp->rcucblist;
-	rcp->rcucblist = *rcp->donetail;
-	*rcp->donetail = NULL;
-	if (rcp->curtail == rcp->donetail)
-		rcp->curtail = &rcp->rcucblist;
-	rcp->donetail = &rcp->rcucblist;
+	list = rcu_ctrlblk.rcucblist;
+	rcu_ctrlblk.rcucblist = *rcu_ctrlblk.donetail;
+	*rcu_ctrlblk.donetail = NULL;
+	if (rcu_ctrlblk.curtail == rcu_ctrlblk.donetail)
+		rcu_ctrlblk.curtail = &rcu_ctrlblk.rcucblist;
+	rcu_ctrlblk.donetail = &rcu_ctrlblk.rcucblist;
 	local_irq_restore(flags);
 
 	/* Invoke the callbacks on the local list. */
@@ -159,85 +121,132 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 		next = list->next;
 		prefetch(next);
 		debug_rcu_head_unqueue(list);
-		local_bh_disable();
-		__rcu_reclaim("", list);
-		local_bh_enable();
+		rcu_reclaim_tiny(list);
 		list = next;
 	}
 }
 
-static __latent_entropy 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.)
+ * synchronize_rcu() from within an RCU read-side critical section.
+ * Therefore, any legal call to synchronize_rcu() is a quiescent state,
+ * and so on a UP system, synchronize_rcu() need do nothing, other than
+ * let the polled APIs know that another grace period elapsed.
+ *
+ * (But Lai Jiangshan points out the benefits of doing might_sleep()
+ * to reduce latency.)
  *
  * Cool, huh?  (Due to Josh Triplett.)
  */
-void synchronize_sched(void)
+void synchronize_rcu(void)
 {
 	RCU_LOCKDEP_WARN(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");
+			 "Illegal synchronize_rcu() in RCU read-side critical section");
+	preempt_disable();
+	WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2);
+	preempt_enable();
 }
-EXPORT_SYMBOL_GPL(synchronize_sched);
+EXPORT_SYMBOL_GPL(synchronize_rcu);
 
 /*
- * Helper function for call_rcu() and call_rcu_bh().
+ * Post an RCU callback to be invoked after the end of an RCU grace
+ * period.  But since we have but one CPU, that would be after any
+ * quiescent state.
  */
-static void __call_rcu(struct rcu_head *head,
-		       rcu_callback_t func,
-		       struct rcu_ctrlblk *rcp)
+void call_rcu(struct rcu_head *head, rcu_callback_t func)
 {
+	static atomic_t doublefrees;
 	unsigned long flags;
 
-	debug_rcu_head_queue(head);
+	if (debug_rcu_head_queue(head)) {
+		if (atomic_inc_return(&doublefrees) < 4) {
+			pr_err("%s(): Double-freed CB %p->%pS()!!!  ", __func__, head, head->func);
+			mem_dump_obj(head);
+		}
+		return;
+	}
+
 	head->func = func;
 	head->next = NULL;
 
 	local_irq_save(flags);
-	*rcp->curtail = head;
-	rcp->curtail = &head->next;
+	*rcu_ctrlblk.curtail = head;
+	rcu_ctrlblk.curtail = &head->next;
 	local_irq_restore(flags);
 
 	if (unlikely(is_idle_task(current))) {
-		/* force scheduling for rcu_sched_qs() */
+		/* force scheduling for rcu_qs() */
 		resched_cpu(0);
 	}
 }
+EXPORT_SYMBOL_GPL(call_rcu);
 
 /*
- * 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.
+ * Store a grace-period-counter "cookie".  For more information,
+ * see the Tree RCU header comment.
  */
-void call_rcu_sched(struct rcu_head *head, rcu_callback_t func)
+void get_completed_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
 {
-	__call_rcu(head, func, &rcu_sched_ctrlblk);
+	rgosp->rgos_norm = RCU_GET_STATE_COMPLETED;
 }
-EXPORT_SYMBOL_GPL(call_rcu_sched);
+EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu_full);
 
 /*
- * Post an RCU bottom-half callback to be invoked after any subsequent
- * quiescent state.
+ * Return a grace-period-counter "cookie".  For more information,
+ * see the Tree RCU header comment.
  */
-void call_rcu_bh(struct rcu_head *head, rcu_callback_t func)
+unsigned long get_state_synchronize_rcu(void)
+{
+	return READ_ONCE(rcu_ctrlblk.gp_seq);
+}
+EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
+
+/*
+ * Return a grace-period-counter "cookie" and ensure that a future grace
+ * period completes.  For more information, see the Tree RCU header comment.
+ */
+unsigned long start_poll_synchronize_rcu(void)
+{
+	unsigned long gp_seq = get_state_synchronize_rcu();
+
+	if (unlikely(is_idle_task(current))) {
+		/* force scheduling for rcu_qs() */
+		resched_cpu(0);
+	}
+	return gp_seq;
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu);
+
+/*
+ * Return true if the grace period corresponding to oldstate has completed
+ * and false otherwise.  For more information, see the Tree RCU header
+ * comment.
+ */
+bool poll_state_synchronize_rcu(unsigned long oldstate)
+{
+	return oldstate == RCU_GET_STATE_COMPLETED || READ_ONCE(rcu_ctrlblk.gp_seq) != oldstate;
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
+
+#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST)
+unsigned long long rcutorture_gather_gp_seqs(void)
+{
+	return READ_ONCE(rcu_ctrlblk.gp_seq) & 0xffffULL;
+}
+EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
+
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
-	__call_rcu(head, func, &rcu_bh_ctrlblk);
+	snprintf(cp, len, "g%04llx", seqs & 0xffffULL);
 }
-EXPORT_SYMBOL_GPL(call_rcu_bh);
+EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
+#endif
 
 void __init rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 	rcu_early_boot_tests();
+	tasks_cblist_init_generic();
 }