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2024-10-12 a5969cabbb4660eab42b6ef0412cbbd1200cf14d 
 kernel/kernel/rcu/tiny.c
....@@ -1,23 +1,10 @@
1
+// SPDX-License-Identifier: GPL-2.0+
12 /*
23  * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
34  *
4
- * This program is free software; you can redistribute it and/or modify
5
- * it under the terms of the GNU General Public License as published by
6
- * the Free Software Foundation; either version 2 of the License, or
7
- * (at your option) any later version.
8
- *
9
- * This program is distributed in the hope that it will be useful,
10
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
11
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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- * GNU General Public License for more details.
13
- *
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- * You should have received a copy of the GNU General Public License
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- * along with this program; if not, you can access it online at
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- * http://www.gnu.org/licenses/gpl-2.0.html.
17
- *
185  * Copyright IBM Corporation, 2008
196  *
20
- * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
7
+ * Author: Paul E. McKenney <paulmck@linux.ibm.com>
218  *
229  * For detailed explanation of Read-Copy Update mechanism see -
2310  *		Documentation/RCU
....@@ -35,6 +22,8 @@
3522 #include <linux/time.h>
3623 #include <linux/cpu.h>
3724 #include <linux/prefetch.h>
25
+#include <linux/slab.h>
26
+#include <linux/mm.h>
3827 
3928 #include "rcu.h"
4029 
....@@ -46,69 +35,27 @@
4635 };
4736 
4837 /* Definition for rcupdate control block. */
49
-static struct rcu_ctrlblk rcu_sched_ctrlblk = {
50
-	.donetail	= &rcu_sched_ctrlblk.rcucblist,
51
-	.curtail	= &rcu_sched_ctrlblk.rcucblist,
38
+static struct rcu_ctrlblk rcu_ctrlblk = {
39
+	.donetail	= &rcu_ctrlblk.rcucblist,
40
+	.curtail	= &rcu_ctrlblk.rcucblist,
5241 };
5342 
54
-static struct rcu_ctrlblk rcu_bh_ctrlblk = {
55
-	.donetail	= &rcu_bh_ctrlblk.rcucblist,
56
-	.curtail	= &rcu_bh_ctrlblk.rcucblist,
57
-};
58
-
59
-void rcu_barrier_bh(void)
43
+void rcu_barrier(void)
6044 {
61
-	wait_rcu_gp(call_rcu_bh);
45
+	wait_rcu_gp(call_rcu);
6246 }
63
-EXPORT_SYMBOL(rcu_barrier_bh);
47
+EXPORT_SYMBOL(rcu_barrier);
6448 
65
-void rcu_barrier_sched(void)
49
+/* Record an rcu quiescent state.  */
50
+void rcu_qs(void)
6651 {
67
-	wait_rcu_gp(call_rcu_sched);
68
-}
69
-EXPORT_SYMBOL(rcu_barrier_sched);
52
+	unsigned long flags;
7053 
71
-/*
72
- * Helper function for rcu_sched_qs() and rcu_bh_qs().
73
- * Also irqs are disabled to avoid confusion due to interrupt handlers
74
- * invoking call_rcu().
75
- */
76
-static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
77
-{
78
-	if (rcp->donetail != rcp->curtail) {
79
-		rcp->donetail = rcp->curtail;
80
-		return 1;
54
+	local_irq_save(flags);
55
+	if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) {
56
+		rcu_ctrlblk.donetail = rcu_ctrlblk.curtail;
57
+		raise_softirq_irqoff(RCU_SOFTIRQ);
8158 	}
82
-
83
-	return 0;
84
-}
85
-
86
-/*
87
- * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
88
- * are at it, given that any rcu quiescent state is also an rcu_bh
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- * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
90
- */
91
-void rcu_sched_qs(void)
92
-{
93
-	unsigned long flags;
94
-
95
-	local_irq_save(flags);
96
-	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
97
-	    rcu_qsctr_help(&rcu_bh_ctrlblk))
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-		raise_softirq(RCU_SOFTIRQ);
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-	local_irq_restore(flags);
100
-}
101
-
102
-/*
103
- * Record an rcu_bh quiescent state.
104
- */
105
-void rcu_bh_qs(void)
106
-{
107
-	unsigned long flags;
108
-
109
-	local_irq_save(flags);
110
-	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
111
-		raise_softirq(RCU_SOFTIRQ);
11259 	local_irq_restore(flags);
11360 }
11461 
....@@ -118,36 +65,60 @@
11865  * be called from hardirq context.  It is normally called from the
11966  * scheduling-clock interrupt.
12067  */
121
-void rcu_check_callbacks(int user)
68
+void rcu_sched_clock_irq(int user)
12269 {
123
-	if (user)
124
-		rcu_sched_qs();
125
-	if (user || !in_softirq())
126
-		rcu_bh_qs();
70
+	if (user) {
71
+		rcu_qs();
72
+	} else if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) {
73
+		set_tsk_need_resched(current);
74
+		set_preempt_need_resched();
75
+	}
12776 }
12877 
12978 /*
130
- * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
131
- * whose grace period has elapsed.
79
+ * Reclaim the specified callback, either by invoking it for non-kfree cases or
80
+ * freeing it directly (for kfree). Return true if kfreeing, false otherwise.
13281  */
133
-static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
82
+static inline bool rcu_reclaim_tiny(struct rcu_head *head)
83
+{
84
+	rcu_callback_t f;
85
+	unsigned long offset = (unsigned long)head->func;
86
+
87
+	rcu_lock_acquire(&rcu_callback_map);
88
+	if (__is_kvfree_rcu_offset(offset)) {
89
+		trace_rcu_invoke_kvfree_callback("", head, offset);
90
+		kvfree((void *)head - offset);
91
+		rcu_lock_release(&rcu_callback_map);
92
+		return true;
93
+	}
94
+
95
+	trace_rcu_invoke_callback("", head);
96
+	f = head->func;
97
+	WRITE_ONCE(head->func, (rcu_callback_t)0L);
98
+	f(head);
99
+	rcu_lock_release(&rcu_callback_map);
100
+	return false;
101
+}
102
+
103
+/* Invoke the RCU callbacks whose grace period has elapsed.  */
104
+static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
134105 {
135106 	struct rcu_head *next, *list;
136107 	unsigned long flags;
137108 
138109 	/* Move the ready-to-invoke callbacks to a local list. */
139110 	local_irq_save(flags);
140
-	if (rcp->donetail == &rcp->rcucblist) {
111
+	if (rcu_ctrlblk.donetail == &rcu_ctrlblk.rcucblist) {
141112 		/* No callbacks ready, so just leave. */
142113 		local_irq_restore(flags);
143114 		return;
144115 	}
145
-	list = rcp->rcucblist;
146
-	rcp->rcucblist = *rcp->donetail;
147
-	*rcp->donetail = NULL;
148
-	if (rcp->curtail == rcp->donetail)
149
-		rcp->curtail = &rcp->rcucblist;
150
-	rcp->donetail = &rcp->rcucblist;
116
+	list = rcu_ctrlblk.rcucblist;
117
+	rcu_ctrlblk.rcucblist = *rcu_ctrlblk.donetail;
118
+	*rcu_ctrlblk.donetail = NULL;
119
+	if (rcu_ctrlblk.curtail == rcu_ctrlblk.donetail)
120
+		rcu_ctrlblk.curtail = &rcu_ctrlblk.rcucblist;
121
+	rcu_ctrlblk.donetail = &rcu_ctrlblk.rcucblist;
151122 	local_irq_restore(flags);
152123 
153124 	/* Invoke the callbacks on the local list. */
....@@ -156,43 +127,37 @@
156127 		prefetch(next);
157128 		debug_rcu_head_unqueue(list);
158129 		local_bh_disable();
159
-		__rcu_reclaim("", list);
130
+		rcu_reclaim_tiny(list);
160131 		local_bh_enable();
161132 		list = next;
162133 	}
163134 }
164135 
165
-static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
166
-{
167
-	__rcu_process_callbacks(&rcu_sched_ctrlblk);
168
-	__rcu_process_callbacks(&rcu_bh_ctrlblk);
169
-}
170
-
171136 /*
172137  * Wait for a grace period to elapse.  But it is illegal to invoke
173
- * synchronize_sched() from within an RCU read-side critical section.
174
- * Therefore, any legal call to synchronize_sched() is a quiescent
175
- * state, and so on a UP system, synchronize_sched() need do nothing.
176
- * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
177
- * benefits of doing might_sleep() to reduce latency.)
138
+ * synchronize_rcu() from within an RCU read-side critical section.
139
+ * Therefore, any legal call to synchronize_rcu() is a quiescent
140
+ * state, and so on a UP system, synchronize_rcu() need do nothing.
141
+ * (But Lai Jiangshan points out the benefits of doing might_sleep()
142
+ * to reduce latency.)
178143  *
179144  * Cool, huh?  (Due to Josh Triplett.)
180145  */
181
-void synchronize_sched(void)
146
+void synchronize_rcu(void)
182147 {
183148 	RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
184149 			 lock_is_held(&rcu_lock_map) ||
185150 			 lock_is_held(&rcu_sched_lock_map),
186
-			 "Illegal synchronize_sched() in RCU read-side critical section");
151
+			 "Illegal synchronize_rcu() in RCU read-side critical section");
187152 }
188
-EXPORT_SYMBOL_GPL(synchronize_sched);
153
+EXPORT_SYMBOL_GPL(synchronize_rcu);
189154 
190155 /*
191
- * Helper function for call_rcu() and call_rcu_bh().
156
+ * Post an RCU callback to be invoked after the end of an RCU grace
157
+ * period.  But since we have but one CPU, that would be after any
158
+ * quiescent state.
192159  */
193
-static void __call_rcu(struct rcu_head *head,
194
-		       rcu_callback_t func,
195
-		       struct rcu_ctrlblk *rcp)
160
+void call_rcu(struct rcu_head *head, rcu_callback_t func)
196161 {
197162 	unsigned long flags;
198163 
....@@ -201,39 +166,20 @@
201166 	head->next = NULL;
202167 
203168 	local_irq_save(flags);
204
-	*rcp->curtail = head;
205
-	rcp->curtail = &head->next;
169
+	*rcu_ctrlblk.curtail = head;
170
+	rcu_ctrlblk.curtail = &head->next;
206171 	local_irq_restore(flags);
207172 
208173 	if (unlikely(is_idle_task(current))) {
209
-		/* force scheduling for rcu_sched_qs() */
174
+		/* force scheduling for rcu_qs() */
210175 		resched_cpu(0);
211176 	}
212177 }
213
-
214
-/*
215
- * Post an RCU callback to be invoked after the end of an RCU-sched grace
216
- * period.  But since we have but one CPU, that would be after any
217
- * quiescent state.
218
- */
219
-void call_rcu_sched(struct rcu_head *head, rcu_callback_t func)
220
-{
221
-	__call_rcu(head, func, &rcu_sched_ctrlblk);
222
-}
223
-EXPORT_SYMBOL_GPL(call_rcu_sched);
224
-
225
-/*
226
- * Post an RCU bottom-half callback to be invoked after any subsequent
227
- * quiescent state.
228
- */
229
-void call_rcu_bh(struct rcu_head *head, rcu_callback_t func)
230
-{
231
-	__call_rcu(head, func, &rcu_bh_ctrlblk);
232
-}
233
-EXPORT_SYMBOL_GPL(call_rcu_bh);
178
+EXPORT_SYMBOL_GPL(call_rcu);
234179 
235180 void __init rcu_init(void)
236181 {
237182 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
238183 	rcu_early_boot_tests();
184
+	srcu_init();
239185 }