Branch data Line data Source code
1 : : /*
2 : : * Read-Copy Update mechanism for mutual exclusion
3 : : *
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
12 : : * GNU General Public License for more details.
13 : : *
14 : : * You should have received a copy of the GNU General Public License
15 : : * along with this program; if not, write to the Free Software
16 : : * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 : : *
18 : : * Copyright IBM Corporation, 2001
19 : : *
20 : : * Authors: Dipankar Sarma <dipankar@in.ibm.com>
21 : : * Manfred Spraul <manfred@colorfullife.com>
22 : : *
23 : : * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
24 : : * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
25 : : * Papers:
26 : : * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
27 : : * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
28 : : *
29 : : * For detailed explanation of Read-Copy Update mechanism see -
30 : : * http://lse.sourceforge.net/locking/rcupdate.html
31 : : *
32 : : */
33 : : #include <linux/types.h>
34 : : #include <linux/kernel.h>
35 : : #include <linux/init.h>
36 : : #include <linux/spinlock.h>
37 : : #include <linux/smp.h>
38 : : #include <linux/interrupt.h>
39 : : #include <linux/sched.h>
40 : : #include <linux/atomic.h>
41 : : #include <linux/bitops.h>
42 : : #include <linux/percpu.h>
43 : : #include <linux/notifier.h>
44 : : #include <linux/cpu.h>
45 : : #include <linux/mutex.h>
46 : : #include <linux/export.h>
47 : : #include <linux/hardirq.h>
48 : : #include <linux/delay.h>
49 : : #include <linux/module.h>
50 : :
51 : : #define CREATE_TRACE_POINTS
52 : : #include <trace/events/rcu.h>
53 : :
54 : : #include "rcu.h"
55 : :
56 : : MODULE_ALIAS("rcupdate");
57 : : #ifdef MODULE_PARAM_PREFIX
58 : : #undef MODULE_PARAM_PREFIX
59 : : #endif
60 : : #define MODULE_PARAM_PREFIX "rcupdate."
61 : :
62 : : module_param(rcu_expedited, int, 0);
63 : :
64 : : #ifdef CONFIG_PREEMPT_RCU
65 : :
66 : : /*
67 : : * Preemptible RCU implementation for rcu_read_lock().
68 : : * Just increment ->rcu_read_lock_nesting, shared state will be updated
69 : : * if we block.
70 : : */
71 : : void __rcu_read_lock(void)
72 : : {
73 : : current->rcu_read_lock_nesting++;
74 : : barrier(); /* critical section after entry code. */
75 : : }
76 : : EXPORT_SYMBOL_GPL(__rcu_read_lock);
77 : :
78 : : /*
79 : : * Preemptible RCU implementation for rcu_read_unlock().
80 : : * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
81 : : * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
82 : : * invoke rcu_read_unlock_special() to clean up after a context switch
83 : : * in an RCU read-side critical section and other special cases.
84 : : */
85 : : void __rcu_read_unlock(void)
86 : : {
87 : : struct task_struct *t = current;
88 : :
89 : : if (t->rcu_read_lock_nesting != 1) {
90 : : --t->rcu_read_lock_nesting;
91 : : } else {
92 : : barrier(); /* critical section before exit code. */
93 : : t->rcu_read_lock_nesting = INT_MIN;
94 : : #ifdef CONFIG_PROVE_RCU_DELAY
95 : : udelay(10); /* Make preemption more probable. */
96 : : #endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
97 : : barrier(); /* assign before ->rcu_read_unlock_special load */
98 : : if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
99 : : rcu_read_unlock_special(t);
100 : : barrier(); /* ->rcu_read_unlock_special load before assign */
101 : : t->rcu_read_lock_nesting = 0;
102 : : }
103 : : #ifdef CONFIG_PROVE_LOCKING
104 : : {
105 : : int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
106 : :
107 : : WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
108 : : }
109 : : #endif /* #ifdef CONFIG_PROVE_LOCKING */
110 : : }
111 : : EXPORT_SYMBOL_GPL(__rcu_read_unlock);
112 : :
113 : : #endif /* #ifdef CONFIG_PREEMPT_RCU */
114 : :
115 : : #ifdef CONFIG_DEBUG_LOCK_ALLOC
116 : : static struct lock_class_key rcu_lock_key;
117 : : struct lockdep_map rcu_lock_map =
118 : : STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
119 : : EXPORT_SYMBOL_GPL(rcu_lock_map);
120 : :
121 : : static struct lock_class_key rcu_bh_lock_key;
122 : : struct lockdep_map rcu_bh_lock_map =
123 : : STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
124 : : EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
125 : :
126 : : static struct lock_class_key rcu_sched_lock_key;
127 : : struct lockdep_map rcu_sched_lock_map =
128 : : STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
129 : : EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
130 : :
131 : : static struct lock_class_key rcu_callback_key;
132 : : struct lockdep_map rcu_callback_map =
133 : : STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
134 : : EXPORT_SYMBOL_GPL(rcu_callback_map);
135 : :
136 : : int notrace debug_lockdep_rcu_enabled(void)
137 : : {
138 : : return rcu_scheduler_active && debug_locks &&
139 : : current->lockdep_recursion == 0;
140 : : }
141 : : EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
142 : :
143 : : /**
144 : : * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
145 : : *
146 : : * Check for bottom half being disabled, which covers both the
147 : : * CONFIG_PROVE_RCU and not cases. Note that if someone uses
148 : : * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
149 : : * will show the situation. This is useful for debug checks in functions
150 : : * that require that they be called within an RCU read-side critical
151 : : * section.
152 : : *
153 : : * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
154 : : *
155 : : * Note that rcu_read_lock() is disallowed if the CPU is either idle or
156 : : * offline from an RCU perspective, so check for those as well.
157 : : */
158 : : int rcu_read_lock_bh_held(void)
159 : : {
160 : : if (!debug_lockdep_rcu_enabled())
161 : : return 1;
162 : : if (!rcu_is_watching())
163 : : return 0;
164 : : if (!rcu_lockdep_current_cpu_online())
165 : : return 0;
166 : : return in_softirq() || irqs_disabled();
167 : : }
168 : : EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
169 : :
170 : : #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
171 : :
172 : : struct rcu_synchronize {
173 : : struct rcu_head head;
174 : : struct completion completion;
175 : : };
176 : :
177 : : /*
178 : : * Awaken the corresponding synchronize_rcu() instance now that a
179 : : * grace period has elapsed.
180 : : */
181 : 0 : static void wakeme_after_rcu(struct rcu_head *head)
182 : : {
183 : : struct rcu_synchronize *rcu;
184 : :
185 : : rcu = container_of(head, struct rcu_synchronize, head);
186 : 162 : complete(&rcu->completion);
187 : 162 : }
188 : :
189 : 0 : void wait_rcu_gp(call_rcu_func_t crf)
190 : : {
191 : : struct rcu_synchronize rcu;
192 : :
193 : : init_rcu_head_on_stack(&rcu.head);
194 : : init_completion(&rcu.completion);
195 : : /* Will wake me after RCU finished. */
196 : 162 : crf(&rcu.head, wakeme_after_rcu);
197 : : /* Wait for it. */
198 : 162 : wait_for_completion(&rcu.completion);
199 : : destroy_rcu_head_on_stack(&rcu.head);
200 : 162 : }
201 : : EXPORT_SYMBOL_GPL(wait_rcu_gp);
202 : :
203 : : #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
204 : : static inline void debug_init_rcu_head(struct rcu_head *head)
205 : : {
206 : : debug_object_init(head, &rcuhead_debug_descr);
207 : : }
208 : :
209 : : static inline void debug_rcu_head_free(struct rcu_head *head)
210 : : {
211 : : debug_object_free(head, &rcuhead_debug_descr);
212 : : }
213 : :
214 : : /*
215 : : * fixup_activate is called when:
216 : : * - an active object is activated
217 : : * - an unknown object is activated (might be a statically initialized object)
218 : : * Activation is performed internally by call_rcu().
219 : : */
220 : : static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
221 : : {
222 : : struct rcu_head *head = addr;
223 : :
224 : : switch (state) {
225 : :
226 : : case ODEBUG_STATE_NOTAVAILABLE:
227 : : /*
228 : : * This is not really a fixup. We just make sure that it is
229 : : * tracked in the object tracker.
230 : : */
231 : : debug_object_init(head, &rcuhead_debug_descr);
232 : : debug_object_activate(head, &rcuhead_debug_descr);
233 : : return 0;
234 : : default:
235 : : return 1;
236 : : }
237 : : }
238 : :
239 : : /**
240 : : * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
241 : : * @head: pointer to rcu_head structure to be initialized
242 : : *
243 : : * This function informs debugobjects of a new rcu_head structure that
244 : : * has been allocated as an auto variable on the stack. This function
245 : : * is not required for rcu_head structures that are statically defined or
246 : : * that are dynamically allocated on the heap. This function has no
247 : : * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
248 : : */
249 : : void init_rcu_head_on_stack(struct rcu_head *head)
250 : : {
251 : : debug_object_init_on_stack(head, &rcuhead_debug_descr);
252 : : }
253 : : EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
254 : :
255 : : /**
256 : : * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
257 : : * @head: pointer to rcu_head structure to be initialized
258 : : *
259 : : * This function informs debugobjects that an on-stack rcu_head structure
260 : : * is about to go out of scope. As with init_rcu_head_on_stack(), this
261 : : * function is not required for rcu_head structures that are statically
262 : : * defined or that are dynamically allocated on the heap. Also as with
263 : : * init_rcu_head_on_stack(), this function has no effect for
264 : : * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
265 : : */
266 : : void destroy_rcu_head_on_stack(struct rcu_head *head)
267 : : {
268 : : debug_object_free(head, &rcuhead_debug_descr);
269 : : }
270 : : EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
271 : :
272 : : struct debug_obj_descr rcuhead_debug_descr = {
273 : : .name = "rcu_head",
274 : : .fixup_activate = rcuhead_fixup_activate,
275 : : };
276 : : EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
277 : : #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
278 : :
279 : : #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
280 : 0 : void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
281 : : unsigned long secs,
282 : : unsigned long c_old, unsigned long c)
283 : : {
284 : : trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
285 : 0 : }
286 : : EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
287 : : #else
288 : : #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
289 : : do { } while (0)
290 : : #endif
291 : :
292 : : #ifdef CONFIG_RCU_STALL_COMMON
293 : :
294 : : #ifdef CONFIG_PROVE_RCU
295 : : #define RCU_STALL_DELAY_DELTA (5 * HZ)
296 : : #else
297 : : #define RCU_STALL_DELAY_DELTA 0
298 : : #endif
299 : :
300 : : int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
301 : : static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
302 : :
303 : : module_param(rcu_cpu_stall_suppress, int, 0644);
304 : : module_param(rcu_cpu_stall_timeout, int, 0644);
305 : :
306 : 0 : int rcu_jiffies_till_stall_check(void)
307 : : {
308 : 223588 : int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
309 : :
310 : : /*
311 : : * Limit check must be consistent with the Kconfig limits
312 : : * for CONFIG_RCU_CPU_STALL_TIMEOUT.
313 : : */
314 [ - + ]: 223588 : if (till_stall_check < 3) {
315 : 0 : ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
316 : : till_stall_check = 3;
317 [ - + ]: 223588 : } else if (till_stall_check > 300) {
318 : 0 : ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
319 : : till_stall_check = 300;
320 : : }
321 : 0 : return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
322 : : }
323 : :
324 : 0 : static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
325 : : {
326 : 0 : rcu_cpu_stall_suppress = 1;
327 : 0 : return NOTIFY_DONE;
328 : : }
329 : :
330 : : static struct notifier_block rcu_panic_block = {
331 : : .notifier_call = rcu_panic,
332 : : };
333 : :
334 : 0 : static int __init check_cpu_stall_init(void)
335 : : {
336 : 0 : atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
337 : 0 : return 0;
338 : : }
339 : : early_initcall(check_cpu_stall_init);
340 : :
341 : : #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
|
