Rev 6082 | Go to most recent revision | Details | Last modification | View Log | RSS feed
Rev | Author | Line No. | Line |
---|---|---|---|
5270 | serge | 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, you can access it online at |
||
16 | * http://www.gnu.org/licenses/gpl-2.0.html. |
||
17 | * |
||
18 | * Copyright IBM Corporation, 2001 |
||
19 | * |
||
20 | * Author: Dipankar Sarma |
||
21 | * |
||
22 | * Based on the original work by Paul McKenney |
||
23 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
||
24 | * Papers: |
||
25 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
||
26 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
||
27 | * |
||
28 | * For detailed explanation of Read-Copy Update mechanism see - |
||
29 | * http://lse.sourceforge.net/locking/rcupdate.html |
||
30 | * |
||
31 | */ |
||
32 | |||
33 | #ifndef __LINUX_RCUPDATE_H |
||
34 | #define __LINUX_RCUPDATE_H |
||
35 | |||
36 | #include |
||
37 | #include |
||
38 | #include |
||
39 | #include |
||
40 | //#include |
||
41 | #include |
||
42 | #include |
||
43 | #include |
||
44 | //#include |
||
45 | #include |
||
46 | #include |
||
47 | #include |
||
48 | |||
49 | extern int rcu_expedited; /* for sysctl */ |
||
50 | |||
51 | enum rcutorture_type { |
||
52 | RCU_FLAVOR, |
||
53 | RCU_BH_FLAVOR, |
||
54 | RCU_SCHED_FLAVOR, |
||
55 | RCU_TASKS_FLAVOR, |
||
56 | SRCU_FLAVOR, |
||
57 | INVALID_RCU_FLAVOR |
||
58 | }; |
||
59 | |||
60 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) |
||
61 | void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, |
||
62 | unsigned long *gpnum, unsigned long *completed); |
||
63 | void rcutorture_record_test_transition(void); |
||
64 | void rcutorture_record_progress(unsigned long vernum); |
||
65 | void do_trace_rcu_torture_read(const char *rcutorturename, |
||
66 | struct rcu_head *rhp, |
||
67 | unsigned long secs, |
||
68 | unsigned long c_old, |
||
69 | unsigned long c); |
||
70 | #else |
||
71 | static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, |
||
72 | int *flags, |
||
73 | unsigned long *gpnum, |
||
74 | unsigned long *completed) |
||
75 | { |
||
76 | *flags = 0; |
||
77 | *gpnum = 0; |
||
78 | *completed = 0; |
||
79 | } |
||
80 | static inline void rcutorture_record_test_transition(void) |
||
81 | { |
||
82 | } |
||
83 | static inline void rcutorture_record_progress(unsigned long vernum) |
||
84 | { |
||
85 | } |
||
86 | #ifdef CONFIG_RCU_TRACE |
||
87 | void do_trace_rcu_torture_read(const char *rcutorturename, |
||
88 | struct rcu_head *rhp, |
||
89 | unsigned long secs, |
||
90 | unsigned long c_old, |
||
91 | unsigned long c); |
||
92 | #else |
||
93 | #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
||
94 | do { } while (0) |
||
95 | #endif |
||
96 | #endif |
||
97 | |||
98 | #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) |
||
99 | #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) |
||
100 | #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) |
||
101 | #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) |
||
102 | #define ulong2long(a) (*(long *)(&(a))) |
||
103 | |||
104 | /* Exported common interfaces */ |
||
105 | |||
106 | #ifdef CONFIG_PREEMPT_RCU |
||
107 | |||
108 | /** |
||
109 | * call_rcu() - Queue an RCU callback for invocation after a grace period. |
||
110 | * @head: structure to be used for queueing the RCU updates. |
||
111 | * @func: actual callback function to be invoked after the grace period |
||
112 | * |
||
113 | * The callback function will be invoked some time after a full grace |
||
114 | * period elapses, in other words after all pre-existing RCU read-side |
||
115 | * critical sections have completed. However, the callback function |
||
116 | * might well execute concurrently with RCU read-side critical sections |
||
117 | * that started after call_rcu() was invoked. RCU read-side critical |
||
118 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
||
119 | * and may be nested. |
||
120 | * |
||
121 | * Note that all CPUs must agree that the grace period extended beyond |
||
122 | * all pre-existing RCU read-side critical section. On systems with more |
||
123 | * than one CPU, this means that when "func()" is invoked, each CPU is |
||
124 | * guaranteed to have executed a full memory barrier since the end of its |
||
125 | * last RCU read-side critical section whose beginning preceded the call |
||
126 | * to call_rcu(). It also means that each CPU executing an RCU read-side |
||
127 | * critical section that continues beyond the start of "func()" must have |
||
128 | * executed a memory barrier after the call_rcu() but before the beginning |
||
129 | * of that RCU read-side critical section. Note that these guarantees |
||
130 | * include CPUs that are offline, idle, or executing in user mode, as |
||
131 | * well as CPUs that are executing in the kernel. |
||
132 | * |
||
133 | * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the |
||
134 | * resulting RCU callback function "func()", then both CPU A and CPU B are |
||
135 | * guaranteed to execute a full memory barrier during the time interval |
||
136 | * between the call to call_rcu() and the invocation of "func()" -- even |
||
137 | * if CPU A and CPU B are the same CPU (but again only if the system has |
||
138 | * more than one CPU). |
||
139 | */ |
||
140 | void call_rcu(struct rcu_head *head, |
||
141 | void (*func)(struct rcu_head *head)); |
||
142 | |||
143 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
||
144 | |||
145 | /* In classic RCU, call_rcu() is just call_rcu_sched(). */ |
||
146 | #define call_rcu call_rcu_sched |
||
147 | |||
148 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
||
149 | |||
150 | /** |
||
151 | * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. |
||
152 | * @head: structure to be used for queueing the RCU updates. |
||
153 | * @func: actual callback function to be invoked after the grace period |
||
154 | * |
||
155 | * The callback function will be invoked some time after a full grace |
||
156 | * period elapses, in other words after all currently executing RCU |
||
157 | * read-side critical sections have completed. call_rcu_bh() assumes |
||
158 | * that the read-side critical sections end on completion of a softirq |
||
159 | * handler. This means that read-side critical sections in process |
||
160 | * context must not be interrupted by softirqs. This interface is to be |
||
161 | * used when most of the read-side critical sections are in softirq context. |
||
162 | * RCU read-side critical sections are delimited by : |
||
163 | * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. |
||
164 | * OR |
||
165 | * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. |
||
166 | * These may be nested. |
||
167 | * |
||
168 | * See the description of call_rcu() for more detailed information on |
||
169 | * memory ordering guarantees. |
||
170 | */ |
||
171 | void call_rcu_bh(struct rcu_head *head, |
||
172 | void (*func)(struct rcu_head *head)); |
||
173 | |||
174 | /** |
||
175 | * call_rcu_sched() - Queue an RCU for invocation after sched grace period. |
||
176 | * @head: structure to be used for queueing the RCU updates. |
||
177 | * @func: actual callback function to be invoked after the grace period |
||
178 | * |
||
179 | * The callback function will be invoked some time after a full grace |
||
180 | * period elapses, in other words after all currently executing RCU |
||
181 | * read-side critical sections have completed. call_rcu_sched() assumes |
||
182 | * that the read-side critical sections end on enabling of preemption |
||
183 | * or on voluntary preemption. |
||
184 | * RCU read-side critical sections are delimited by : |
||
185 | * - rcu_read_lock_sched() and rcu_read_unlock_sched(), |
||
186 | * OR |
||
187 | * anything that disables preemption. |
||
188 | * These may be nested. |
||
189 | * |
||
190 | * See the description of call_rcu() for more detailed information on |
||
191 | * memory ordering guarantees. |
||
192 | */ |
||
193 | void call_rcu_sched(struct rcu_head *head, |
||
194 | void (*func)(struct rcu_head *rcu)); |
||
195 | |||
196 | void synchronize_sched(void); |
||
197 | |||
198 | /** |
||
199 | * call_rcu_tasks() - Queue an RCU for invocation task-based grace period |
||
200 | * @head: structure to be used for queueing the RCU updates. |
||
201 | * @func: actual callback function to be invoked after the grace period |
||
202 | * |
||
203 | * The callback function will be invoked some time after a full grace |
||
204 | * period elapses, in other words after all currently executing RCU |
||
205 | * read-side critical sections have completed. call_rcu_tasks() assumes |
||
206 | * that the read-side critical sections end at a voluntary context |
||
207 | * switch (not a preemption!), entry into idle, or transition to usermode |
||
208 | * execution. As such, there are no read-side primitives analogous to |
||
209 | * rcu_read_lock() and rcu_read_unlock() because this primitive is intended |
||
210 | * to determine that all tasks have passed through a safe state, not so |
||
211 | * much for data-strcuture synchronization. |
||
212 | * |
||
213 | * See the description of call_rcu() for more detailed information on |
||
214 | * memory ordering guarantees. |
||
215 | */ |
||
216 | void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head)); |
||
217 | void synchronize_rcu_tasks(void); |
||
218 | void rcu_barrier_tasks(void); |
||
219 | |||
220 | #ifdef CONFIG_PREEMPT_RCU |
||
221 | |||
222 | void __rcu_read_lock(void); |
||
223 | void __rcu_read_unlock(void); |
||
224 | void rcu_read_unlock_special(struct task_struct *t); |
||
225 | void synchronize_rcu(void); |
||
226 | |||
227 | /* |
||
228 | * Defined as a macro as it is a very low level header included from |
||
229 | * areas that don't even know about current. This gives the rcu_read_lock() |
||
230 | * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other |
||
231 | * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. |
||
232 | */ |
||
233 | #define rcu_preempt_depth() (current->rcu_read_lock_nesting) |
||
234 | |||
235 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
||
236 | |||
237 | static inline void __rcu_read_lock(void) |
||
238 | { |
||
239 | preempt_disable(); |
||
240 | } |
||
241 | |||
242 | static inline void __rcu_read_unlock(void) |
||
243 | { |
||
244 | preempt_enable(); |
||
245 | } |
||
246 | |||
247 | static inline void synchronize_rcu(void) |
||
248 | { |
||
249 | synchronize_sched(); |
||
250 | } |
||
251 | |||
252 | static inline int rcu_preempt_depth(void) |
||
253 | { |
||
254 | return 0; |
||
255 | } |
||
256 | |||
257 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
||
258 | |||
259 | /* Internal to kernel */ |
||
260 | void rcu_init(void); |
||
261 | void rcu_sched_qs(void); |
||
262 | void rcu_bh_qs(void); |
||
263 | void rcu_check_callbacks(int user); |
||
264 | struct notifier_block; |
||
265 | void rcu_idle_enter(void); |
||
266 | void rcu_idle_exit(void); |
||
267 | void rcu_irq_enter(void); |
||
268 | void rcu_irq_exit(void); |
||
269 | |||
270 | #ifdef CONFIG_RCU_STALL_COMMON |
||
271 | void rcu_sysrq_start(void); |
||
272 | void rcu_sysrq_end(void); |
||
273 | #else /* #ifdef CONFIG_RCU_STALL_COMMON */ |
||
274 | static inline void rcu_sysrq_start(void) |
||
275 | { |
||
276 | } |
||
277 | static inline void rcu_sysrq_end(void) |
||
278 | { |
||
279 | } |
||
280 | #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ |
||
281 | |||
282 | #ifdef CONFIG_RCU_USER_QS |
||
283 | void rcu_user_enter(void); |
||
284 | void rcu_user_exit(void); |
||
285 | #else |
||
286 | static inline void rcu_user_enter(void) { } |
||
287 | static inline void rcu_user_exit(void) { } |
||
288 | static inline void rcu_user_hooks_switch(struct task_struct *prev, |
||
289 | struct task_struct *next) { } |
||
290 | #endif /* CONFIG_RCU_USER_QS */ |
||
291 | |||
292 | #ifdef CONFIG_RCU_NOCB_CPU |
||
293 | void rcu_init_nohz(void); |
||
294 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
||
295 | static inline void rcu_init_nohz(void) |
||
296 | { |
||
297 | } |
||
298 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
||
299 | |||
300 | /** |
||
301 | * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers |
||
302 | * @a: Code that RCU needs to pay attention to. |
||
303 | * |
||
304 | * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden |
||
305 | * in the inner idle loop, that is, between the rcu_idle_enter() and |
||
306 | * the rcu_idle_exit() -- RCU will happily ignore any such read-side |
||
307 | * critical sections. However, things like powertop need tracepoints |
||
308 | * in the inner idle loop. |
||
309 | * |
||
310 | * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) |
||
311 | * will tell RCU that it needs to pay attending, invoke its argument |
||
312 | * (in this example, a call to the do_something_with_RCU() function), |
||
313 | * and then tell RCU to go back to ignoring this CPU. It is permissible |
||
314 | * to nest RCU_NONIDLE() wrappers, but the nesting level is currently |
||
315 | * quite limited. If deeper nesting is required, it will be necessary |
||
316 | * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. |
||
317 | */ |
||
318 | #define RCU_NONIDLE(a) \ |
||
319 | do { \ |
||
320 | rcu_irq_enter(); \ |
||
321 | do { a; } while (0); \ |
||
322 | rcu_irq_exit(); \ |
||
323 | } while (0) |
||
324 | |||
325 | /* |
||
326 | * Note a voluntary context switch for RCU-tasks benefit. This is a |
||
327 | * macro rather than an inline function to avoid #include hell. |
||
328 | */ |
||
329 | #ifdef CONFIG_TASKS_RCU |
||
330 | #define TASKS_RCU(x) x |
||
331 | extern struct srcu_struct tasks_rcu_exit_srcu; |
||
332 | #define rcu_note_voluntary_context_switch(t) \ |
||
333 | do { \ |
||
334 | if (ACCESS_ONCE((t)->rcu_tasks_holdout)) \ |
||
335 | ACCESS_ONCE((t)->rcu_tasks_holdout) = false; \ |
||
336 | } while (0) |
||
337 | #else /* #ifdef CONFIG_TASKS_RCU */ |
||
338 | #define TASKS_RCU(x) do { } while (0) |
||
339 | #define rcu_note_voluntary_context_switch(t) do { } while (0) |
||
340 | #endif /* #else #ifdef CONFIG_TASKS_RCU */ |
||
341 | |||
342 | /** |
||
343 | * cond_resched_rcu_qs - Report potential quiescent states to RCU |
||
344 | * |
||
345 | * This macro resembles cond_resched(), except that it is defined to |
||
346 | * report potential quiescent states to RCU-tasks even if the cond_resched() |
||
347 | * machinery were to be shut off, as some advocate for PREEMPT kernels. |
||
348 | */ |
||
349 | #define cond_resched_rcu_qs() \ |
||
350 | do { \ |
||
351 | if (!cond_resched()) \ |
||
352 | rcu_note_voluntary_context_switch(current); \ |
||
353 | } while (0) |
||
354 | |||
355 | #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) |
||
356 | bool __rcu_is_watching(void); |
||
357 | #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */ |
||
358 | |||
359 | /* |
||
360 | * Infrastructure to implement the synchronize_() primitives in |
||
361 | * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. |
||
362 | */ |
||
363 | |||
364 | typedef void call_rcu_func_t(struct rcu_head *head, |
||
365 | void (*func)(struct rcu_head *head)); |
||
366 | void wait_rcu_gp(call_rcu_func_t crf); |
||
367 | |||
368 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) |
||
369 | #include |
||
370 | #elif defined(CONFIG_TINY_RCU) |
||
371 | #include |
||
372 | #else |
||
373 | #error "Unknown RCU implementation specified to kernel configuration" |
||
374 | #endif |
||
375 | |||
376 | /* |
||
377 | * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic |
||
378 | * initialization and destruction of rcu_head on the stack. rcu_head structures |
||
379 | * allocated dynamically in the heap or defined statically don't need any |
||
380 | * initialization. |
||
381 | */ |
||
382 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
||
383 | void init_rcu_head(struct rcu_head *head); |
||
384 | void destroy_rcu_head(struct rcu_head *head); |
||
385 | void init_rcu_head_on_stack(struct rcu_head *head); |
||
386 | void destroy_rcu_head_on_stack(struct rcu_head *head); |
||
387 | #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
||
388 | static inline void init_rcu_head(struct rcu_head *head) |
||
389 | { |
||
390 | } |
||
391 | |||
392 | static inline void destroy_rcu_head(struct rcu_head *head) |
||
393 | { |
||
394 | } |
||
395 | |||
396 | static inline void init_rcu_head_on_stack(struct rcu_head *head) |
||
397 | { |
||
398 | } |
||
399 | |||
400 | static inline void destroy_rcu_head_on_stack(struct rcu_head *head) |
||
401 | { |
||
402 | } |
||
403 | #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
||
404 | |||
405 | #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) |
||
406 | bool rcu_lockdep_current_cpu_online(void); |
||
407 | #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
||
408 | static inline bool rcu_lockdep_current_cpu_online(void) |
||
409 | { |
||
410 | return true; |
||
411 | } |
||
412 | #endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ |
||
413 | |||
414 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
||
415 | |||
416 | static inline void rcu_lock_acquire(struct lockdep_map *map) |
||
417 | { |
||
418 | lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); |
||
419 | } |
||
420 | |||
421 | static inline void rcu_lock_release(struct lockdep_map *map) |
||
422 | { |
||
423 | lock_release(map, 1, _THIS_IP_); |
||
424 | } |
||
425 | |||
426 | extern struct lockdep_map rcu_lock_map; |
||
427 | extern struct lockdep_map rcu_bh_lock_map; |
||
428 | extern struct lockdep_map rcu_sched_lock_map; |
||
429 | extern struct lockdep_map rcu_callback_map; |
||
430 | int debug_lockdep_rcu_enabled(void); |
||
431 | |||
432 | int rcu_read_lock_held(void); |
||
433 | int rcu_read_lock_bh_held(void); |
||
434 | |||
435 | /** |
||
436 | * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? |
||
437 | * |
||
438 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an |
||
439 | * RCU-sched read-side critical section. In absence of |
||
440 | * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side |
||
441 | * critical section unless it can prove otherwise. Note that disabling |
||
442 | * of preemption (including disabling irqs) counts as an RCU-sched |
||
443 | * read-side critical section. This is useful for debug checks in functions |
||
444 | * that required that they be called within an RCU-sched read-side |
||
445 | * critical section. |
||
446 | * |
||
447 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot |
||
448 | * and while lockdep is disabled. |
||
449 | * |
||
450 | * Note that if the CPU is in the idle loop from an RCU point of |
||
451 | * view (ie: that we are in the section between rcu_idle_enter() and |
||
452 | * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU |
||
453 | * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs |
||
454 | * that are in such a section, considering these as in extended quiescent |
||
455 | * state, so such a CPU is effectively never in an RCU read-side critical |
||
456 | * section regardless of what RCU primitives it invokes. This state of |
||
457 | * affairs is required --- we need to keep an RCU-free window in idle |
||
458 | * where the CPU may possibly enter into low power mode. This way we can |
||
459 | * notice an extended quiescent state to other CPUs that started a grace |
||
460 | * period. Otherwise we would delay any grace period as long as we run in |
||
461 | * the idle task. |
||
462 | * |
||
463 | * Similarly, we avoid claiming an SRCU read lock held if the current |
||
464 | * CPU is offline. |
||
465 | */ |
||
466 | #ifdef CONFIG_PREEMPT_COUNT |
||
467 | static inline int rcu_read_lock_sched_held(void) |
||
468 | { |
||
469 | int lockdep_opinion = 0; |
||
470 | |||
471 | if (!debug_lockdep_rcu_enabled()) |
||
472 | return 1; |
||
473 | if (!rcu_is_watching()) |
||
474 | return 0; |
||
475 | if (!rcu_lockdep_current_cpu_online()) |
||
476 | return 0; |
||
477 | if (debug_locks) |
||
478 | lockdep_opinion = lock_is_held(&rcu_sched_lock_map); |
||
479 | return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); |
||
480 | } |
||
481 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
||
482 | static inline int rcu_read_lock_sched_held(void) |
||
483 | { |
||
484 | return 1; |
||
485 | } |
||
486 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
||
487 | |||
488 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
||
489 | |||
490 | # define rcu_lock_acquire(a) do { } while (0) |
||
491 | # define rcu_lock_release(a) do { } while (0) |
||
492 | |||
493 | static inline int rcu_read_lock_held(void) |
||
494 | { |
||
495 | return 1; |
||
496 | } |
||
497 | |||
498 | static inline int rcu_read_lock_bh_held(void) |
||
499 | { |
||
500 | return 1; |
||
501 | } |
||
502 | |||
503 | #ifdef CONFIG_PREEMPT_COUNT |
||
504 | static inline int rcu_read_lock_sched_held(void) |
||
505 | { |
||
506 | return preempt_count() != 0 || irqs_disabled(); |
||
507 | } |
||
508 | #else /* #ifdef CONFIG_PREEMPT_COUNT */ |
||
509 | static inline int rcu_read_lock_sched_held(void) |
||
510 | { |
||
511 | return 1; |
||
512 | } |
||
513 | #endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ |
||
514 | |||
515 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
||
516 | |||
517 | #ifdef CONFIG_PROVE_RCU |
||
518 | |||
519 | /** |
||
520 | * rcu_lockdep_assert - emit lockdep splat if specified condition not met |
||
521 | * @c: condition to check |
||
522 | * @s: informative message |
||
523 | */ |
||
524 | #define rcu_lockdep_assert(c, s) \ |
||
525 | do { \ |
||
526 | static bool __section(.data.unlikely) __warned; \ |
||
527 | if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ |
||
528 | __warned = true; \ |
||
529 | lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ |
||
530 | } \ |
||
531 | } while (0) |
||
532 | |||
533 | #if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) |
||
534 | static inline void rcu_preempt_sleep_check(void) |
||
535 | { |
||
536 | rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), |
||
537 | "Illegal context switch in RCU read-side critical section"); |
||
538 | } |
||
539 | #else /* #ifdef CONFIG_PROVE_RCU */ |
||
540 | static inline void rcu_preempt_sleep_check(void) |
||
541 | { |
||
542 | } |
||
543 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
||
544 | |||
545 | #define rcu_sleep_check() \ |
||
546 | do { \ |
||
547 | rcu_preempt_sleep_check(); \ |
||
548 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ |
||
549 | "Illegal context switch in RCU-bh read-side critical section"); \ |
||
550 | rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ |
||
551 | "Illegal context switch in RCU-sched read-side critical section"); \ |
||
552 | } while (0) |
||
553 | |||
554 | #else /* #ifdef CONFIG_PROVE_RCU */ |
||
555 | |||
556 | #define rcu_lockdep_assert(c, s) do { } while (0) |
||
557 | #define rcu_sleep_check() do { } while (0) |
||
558 | |||
559 | #endif /* #else #ifdef CONFIG_PROVE_RCU */ |
||
560 | |||
561 | /* |
||
562 | * Helper functions for rcu_dereference_check(), rcu_dereference_protected() |
||
563 | * and rcu_assign_pointer(). Some of these could be folded into their |
||
564 | * callers, but they are left separate in order to ease introduction of |
||
565 | * multiple flavors of pointers to match the multiple flavors of RCU |
||
566 | * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in |
||
567 | * the future. |
||
568 | */ |
||
569 | |||
570 | #ifdef __CHECKER__ |
||
571 | #define rcu_dereference_sparse(p, space) \ |
||
572 | ((void)(((typeof(*p) space *)p) == p)) |
||
573 | #else /* #ifdef __CHECKER__ */ |
||
574 | #define rcu_dereference_sparse(p, space) |
||
575 | #endif /* #else #ifdef __CHECKER__ */ |
||
576 | |||
577 | #define __rcu_access_pointer(p, space) \ |
||
578 | ({ \ |
||
579 | typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \ |
||
580 | rcu_dereference_sparse(p, space); \ |
||
581 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
||
582 | }) |
||
583 | #define __rcu_dereference_check(p, c, space) \ |
||
584 | ({ \ |
||
585 | typeof(*p) *_________p1 = (typeof(*p) *__force)ACCESS_ONCE(p); \ |
||
586 | rcu_lockdep_assert(c, "suspicious rcu_dereference_check() usage"); \ |
||
587 | rcu_dereference_sparse(p, space); \ |
||
588 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ |
||
589 | ((typeof(*p) __force __kernel *)(_________p1)); \ |
||
590 | }) |
||
591 | #define __rcu_dereference_protected(p, c, space) \ |
||
592 | ({ \ |
||
593 | rcu_lockdep_assert(c, "suspicious rcu_dereference_protected() usage"); \ |
||
594 | rcu_dereference_sparse(p, space); \ |
||
595 | ((typeof(*p) __force __kernel *)(p)); \ |
||
596 | }) |
||
597 | |||
598 | #define __rcu_access_index(p, space) \ |
||
599 | ({ \ |
||
600 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
||
601 | rcu_dereference_sparse(p, space); \ |
||
602 | (_________p1); \ |
||
603 | }) |
||
604 | #define __rcu_dereference_index_check(p, c) \ |
||
605 | ({ \ |
||
606 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
||
607 | rcu_lockdep_assert(c, \ |
||
608 | "suspicious rcu_dereference_index_check() usage"); \ |
||
609 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ |
||
610 | (_________p1); \ |
||
611 | }) |
||
612 | |||
613 | /** |
||
614 | * RCU_INITIALIZER() - statically initialize an RCU-protected global variable |
||
615 | * @v: The value to statically initialize with. |
||
616 | */ |
||
617 | #define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v) |
||
618 | |||
619 | /** |
||
620 | * lockless_dereference() - safely load a pointer for later dereference |
||
621 | * @p: The pointer to load |
||
622 | * |
||
623 | * Similar to rcu_dereference(), but for situations where the pointed-to |
||
624 | * object's lifetime is managed by something other than RCU. That |
||
625 | * "something other" might be reference counting or simple immortality. |
||
626 | */ |
||
627 | #define lockless_dereference(p) \ |
||
628 | ({ \ |
||
629 | typeof(p) _________p1 = ACCESS_ONCE(p); \ |
||
630 | smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ |
||
631 | (_________p1); \ |
||
632 | }) |
||
633 | |||
634 | /** |
||
635 | * rcu_assign_pointer() - assign to RCU-protected pointer |
||
636 | * @p: pointer to assign to |
||
637 | * @v: value to assign (publish) |
||
638 | * |
||
639 | * Assigns the specified value to the specified RCU-protected |
||
640 | * pointer, ensuring that any concurrent RCU readers will see |
||
641 | * any prior initialization. |
||
642 | * |
||
643 | * Inserts memory barriers on architectures that require them |
||
644 | * (which is most of them), and also prevents the compiler from |
||
645 | * reordering the code that initializes the structure after the pointer |
||
646 | * assignment. More importantly, this call documents which pointers |
||
647 | * will be dereferenced by RCU read-side code. |
||
648 | * |
||
649 | * In some special cases, you may use RCU_INIT_POINTER() instead |
||
650 | * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due |
||
651 | * to the fact that it does not constrain either the CPU or the compiler. |
||
652 | * That said, using RCU_INIT_POINTER() when you should have used |
||
653 | * rcu_assign_pointer() is a very bad thing that results in |
||
654 | * impossible-to-diagnose memory corruption. So please be careful. |
||
655 | * See the RCU_INIT_POINTER() comment header for details. |
||
656 | * |
||
657 | * Note that rcu_assign_pointer() evaluates each of its arguments only |
||
658 | * once, appearances notwithstanding. One of the "extra" evaluations |
||
659 | * is in typeof() and the other visible only to sparse (__CHECKER__), |
||
660 | * neither of which actually execute the argument. As with most cpp |
||
661 | * macros, this execute-arguments-only-once property is important, so |
||
662 | * please be careful when making changes to rcu_assign_pointer() and the |
||
663 | * other macros that it invokes. |
||
664 | */ |
||
665 | #define rcu_assign_pointer(p, v) smp_store_release(&p, RCU_INITIALIZER(v)) |
||
666 | |||
667 | /** |
||
668 | * rcu_access_pointer() - fetch RCU pointer with no dereferencing |
||
669 | * @p: The pointer to read |
||
670 | * |
||
671 | * Return the value of the specified RCU-protected pointer, but omit the |
||
672 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
||
673 | * when the value of this pointer is accessed, but the pointer is not |
||
674 | * dereferenced, for example, when testing an RCU-protected pointer against |
||
675 | * NULL. Although rcu_access_pointer() may also be used in cases where |
||
676 | * update-side locks prevent the value of the pointer from changing, you |
||
677 | * should instead use rcu_dereference_protected() for this use case. |
||
678 | * |
||
679 | * It is also permissible to use rcu_access_pointer() when read-side |
||
680 | * access to the pointer was removed at least one grace period ago, as |
||
681 | * is the case in the context of the RCU callback that is freeing up |
||
682 | * the data, or after a synchronize_rcu() returns. This can be useful |
||
683 | * when tearing down multi-linked structures after a grace period |
||
684 | * has elapsed. |
||
685 | */ |
||
686 | #define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) |
||
687 | |||
688 | /** |
||
689 | * rcu_dereference_check() - rcu_dereference with debug checking |
||
690 | * @p: The pointer to read, prior to dereferencing |
||
691 | * @c: The conditions under which the dereference will take place |
||
692 | * |
||
693 | * Do an rcu_dereference(), but check that the conditions under which the |
||
694 | * dereference will take place are correct. Typically the conditions |
||
695 | * indicate the various locking conditions that should be held at that |
||
696 | * point. The check should return true if the conditions are satisfied. |
||
697 | * An implicit check for being in an RCU read-side critical section |
||
698 | * (rcu_read_lock()) is included. |
||
699 | * |
||
700 | * For example: |
||
701 | * |
||
702 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); |
||
703 | * |
||
704 | * could be used to indicate to lockdep that foo->bar may only be dereferenced |
||
705 | * if either rcu_read_lock() is held, or that the lock required to replace |
||
706 | * the bar struct at foo->bar is held. |
||
707 | * |
||
708 | * Note that the list of conditions may also include indications of when a lock |
||
709 | * need not be held, for example during initialisation or destruction of the |
||
710 | * target struct: |
||
711 | * |
||
712 | * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || |
||
713 | * atomic_read(&foo->usage) == 0); |
||
714 | * |
||
715 | * Inserts memory barriers on architectures that require them |
||
716 | * (currently only the Alpha), prevents the compiler from refetching |
||
717 | * (and from merging fetches), and, more importantly, documents exactly |
||
718 | * which pointers are protected by RCU and checks that the pointer is |
||
719 | * annotated as __rcu. |
||
720 | */ |
||
721 | #define rcu_dereference_check(p, c) \ |
||
722 | __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) |
||
723 | |||
724 | /** |
||
725 | * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking |
||
726 | * @p: The pointer to read, prior to dereferencing |
||
727 | * @c: The conditions under which the dereference will take place |
||
728 | * |
||
729 | * This is the RCU-bh counterpart to rcu_dereference_check(). |
||
730 | */ |
||
731 | #define rcu_dereference_bh_check(p, c) \ |
||
732 | __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) |
||
733 | |||
734 | /** |
||
735 | * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking |
||
736 | * @p: The pointer to read, prior to dereferencing |
||
737 | * @c: The conditions under which the dereference will take place |
||
738 | * |
||
739 | * This is the RCU-sched counterpart to rcu_dereference_check(). |
||
740 | */ |
||
741 | #define rcu_dereference_sched_check(p, c) \ |
||
742 | __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ |
||
743 | __rcu) |
||
744 | |||
745 | #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ |
||
746 | |||
747 | /* |
||
748 | * The tracing infrastructure traces RCU (we want that), but unfortunately |
||
749 | * some of the RCU checks causes tracing to lock up the system. |
||
750 | * |
||
751 | * The tracing version of rcu_dereference_raw() must not call |
||
752 | * rcu_read_lock_held(). |
||
753 | */ |
||
754 | #define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) |
||
755 | |||
756 | /** |
||
757 | * rcu_access_index() - fetch RCU index with no dereferencing |
||
758 | * @p: The index to read |
||
759 | * |
||
760 | * Return the value of the specified RCU-protected index, but omit the |
||
761 | * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful |
||
762 | * when the value of this index is accessed, but the index is not |
||
763 | * dereferenced, for example, when testing an RCU-protected index against |
||
764 | * -1. Although rcu_access_index() may also be used in cases where |
||
765 | * update-side locks prevent the value of the index from changing, you |
||
766 | * should instead use rcu_dereference_index_protected() for this use case. |
||
767 | */ |
||
768 | #define rcu_access_index(p) __rcu_access_index((p), __rcu) |
||
769 | |||
770 | /** |
||
771 | * rcu_dereference_index_check() - rcu_dereference for indices with debug checking |
||
772 | * @p: The pointer to read, prior to dereferencing |
||
773 | * @c: The conditions under which the dereference will take place |
||
774 | * |
||
775 | * Similar to rcu_dereference_check(), but omits the sparse checking. |
||
776 | * This allows rcu_dereference_index_check() to be used on integers, |
||
777 | * which can then be used as array indices. Attempting to use |
||
778 | * rcu_dereference_check() on an integer will give compiler warnings |
||
779 | * because the sparse address-space mechanism relies on dereferencing |
||
780 | * the RCU-protected pointer. Dereferencing integers is not something |
||
781 | * that even gcc will put up with. |
||
782 | * |
||
783 | * Note that this function does not implicitly check for RCU read-side |
||
784 | * critical sections. If this function gains lots of uses, it might |
||
785 | * make sense to provide versions for each flavor of RCU, but it does |
||
786 | * not make sense as of early 2010. |
||
787 | */ |
||
788 | #define rcu_dereference_index_check(p, c) \ |
||
789 | __rcu_dereference_index_check((p), (c)) |
||
790 | |||
791 | /** |
||
792 | * rcu_dereference_protected() - fetch RCU pointer when updates prevented |
||
793 | * @p: The pointer to read, prior to dereferencing |
||
794 | * @c: The conditions under which the dereference will take place |
||
795 | * |
||
796 | * Return the value of the specified RCU-protected pointer, but omit |
||
797 | * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This |
||
798 | * is useful in cases where update-side locks prevent the value of the |
||
799 | * pointer from changing. Please note that this primitive does -not- |
||
800 | * prevent the compiler from repeating this reference or combining it |
||
801 | * with other references, so it should not be used without protection |
||
802 | * of appropriate locks. |
||
803 | * |
||
804 | * This function is only for update-side use. Using this function |
||
805 | * when protected only by rcu_read_lock() will result in infrequent |
||
806 | * but very ugly failures. |
||
807 | */ |
||
808 | #define rcu_dereference_protected(p, c) \ |
||
809 | __rcu_dereference_protected((p), (c), __rcu) |
||
810 | |||
811 | |||
812 | /** |
||
813 | * rcu_dereference() - fetch RCU-protected pointer for dereferencing |
||
814 | * @p: The pointer to read, prior to dereferencing |
||
815 | * |
||
816 | * This is a simple wrapper around rcu_dereference_check(). |
||
817 | */ |
||
818 | #define rcu_dereference(p) rcu_dereference_check(p, 0) |
||
819 | |||
820 | /** |
||
821 | * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing |
||
822 | * @p: The pointer to read, prior to dereferencing |
||
823 | * |
||
824 | * Makes rcu_dereference_check() do the dirty work. |
||
825 | */ |
||
826 | #define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) |
||
827 | |||
828 | /** |
||
829 | * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing |
||
830 | * @p: The pointer to read, prior to dereferencing |
||
831 | * |
||
832 | * Makes rcu_dereference_check() do the dirty work. |
||
833 | */ |
||
834 | #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) |
||
835 | |||
836 | /** |
||
837 | * rcu_read_lock() - mark the beginning of an RCU read-side critical section |
||
838 | * |
||
839 | * When synchronize_rcu() is invoked on one CPU while other CPUs |
||
840 | * are within RCU read-side critical sections, then the |
||
841 | * synchronize_rcu() is guaranteed to block until after all the other |
||
842 | * CPUs exit their critical sections. Similarly, if call_rcu() is invoked |
||
843 | * on one CPU while other CPUs are within RCU read-side critical |
||
844 | * sections, invocation of the corresponding RCU callback is deferred |
||
845 | * until after the all the other CPUs exit their critical sections. |
||
846 | * |
||
847 | * Note, however, that RCU callbacks are permitted to run concurrently |
||
848 | * with new RCU read-side critical sections. One way that this can happen |
||
849 | * is via the following sequence of events: (1) CPU 0 enters an RCU |
||
850 | * read-side critical section, (2) CPU 1 invokes call_rcu() to register |
||
851 | * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, |
||
852 | * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU |
||
853 | * callback is invoked. This is legal, because the RCU read-side critical |
||
854 | * section that was running concurrently with the call_rcu() (and which |
||
855 | * therefore might be referencing something that the corresponding RCU |
||
856 | * callback would free up) has completed before the corresponding |
||
857 | * RCU callback is invoked. |
||
858 | * |
||
859 | * RCU read-side critical sections may be nested. Any deferred actions |
||
860 | * will be deferred until the outermost RCU read-side critical section |
||
861 | * completes. |
||
862 | * |
||
863 | * You can avoid reading and understanding the next paragraph by |
||
864 | * following this rule: don't put anything in an rcu_read_lock() RCU |
||
865 | * read-side critical section that would block in a !PREEMPT kernel. |
||
866 | * But if you want the full story, read on! |
||
867 | * |
||
868 | * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), |
||
869 | * it is illegal to block while in an RCU read-side critical section. |
||
870 | * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT |
||
871 | * kernel builds, RCU read-side critical sections may be preempted, |
||
872 | * but explicit blocking is illegal. Finally, in preemptible RCU |
||
873 | * implementations in real-time (with -rt patchset) kernel builds, RCU |
||
874 | * read-side critical sections may be preempted and they may also block, but |
||
875 | * only when acquiring spinlocks that are subject to priority inheritance. |
||
876 | */ |
||
877 | static inline void rcu_read_lock(void) |
||
878 | { |
||
879 | __rcu_read_lock(); |
||
880 | __acquire(RCU); |
||
881 | rcu_lock_acquire(&rcu_lock_map); |
||
882 | rcu_lockdep_assert(rcu_is_watching(), |
||
883 | "rcu_read_lock() used illegally while idle"); |
||
884 | } |
||
885 | |||
886 | /* |
||
887 | * So where is rcu_write_lock()? It does not exist, as there is no |
||
888 | * way for writers to lock out RCU readers. This is a feature, not |
||
889 | * a bug -- this property is what provides RCU's performance benefits. |
||
890 | * Of course, writers must coordinate with each other. The normal |
||
891 | * spinlock primitives work well for this, but any other technique may be |
||
892 | * used as well. RCU does not care how the writers keep out of each |
||
893 | * others' way, as long as they do so. |
||
894 | */ |
||
895 | |||
896 | /** |
||
897 | * rcu_read_unlock() - marks the end of an RCU read-side critical section. |
||
898 | * |
||
899 | * In most situations, rcu_read_unlock() is immune from deadlock. |
||
900 | * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() |
||
901 | * is responsible for deboosting, which it does via rt_mutex_unlock(). |
||
902 | * Unfortunately, this function acquires the scheduler's runqueue and |
||
903 | * priority-inheritance spinlocks. This means that deadlock could result |
||
904 | * if the caller of rcu_read_unlock() already holds one of these locks or |
||
905 | * any lock that is ever acquired while holding them; or any lock which |
||
906 | * can be taken from interrupt context because rcu_boost()->rt_mutex_lock() |
||
907 | * does not disable irqs while taking ->wait_lock. |
||
908 | * |
||
909 | * That said, RCU readers are never priority boosted unless they were |
||
910 | * preempted. Therefore, one way to avoid deadlock is to make sure |
||
911 | * that preemption never happens within any RCU read-side critical |
||
912 | * section whose outermost rcu_read_unlock() is called with one of |
||
913 | * rt_mutex_unlock()'s locks held. Such preemption can be avoided in |
||
914 | * a number of ways, for example, by invoking preempt_disable() before |
||
915 | * critical section's outermost rcu_read_lock(). |
||
916 | * |
||
917 | * Given that the set of locks acquired by rt_mutex_unlock() might change |
||
918 | * at any time, a somewhat more future-proofed approach is to make sure |
||
919 | * that that preemption never happens within any RCU read-side critical |
||
920 | * section whose outermost rcu_read_unlock() is called with irqs disabled. |
||
921 | * This approach relies on the fact that rt_mutex_unlock() currently only |
||
922 | * acquires irq-disabled locks. |
||
923 | * |
||
924 | * The second of these two approaches is best in most situations, |
||
925 | * however, the first approach can also be useful, at least to those |
||
926 | * developers willing to keep abreast of the set of locks acquired by |
||
927 | * rt_mutex_unlock(). |
||
928 | * |
||
929 | * See rcu_read_lock() for more information. |
||
930 | */ |
||
931 | static inline void rcu_read_unlock(void) |
||
932 | { |
||
933 | rcu_lockdep_assert(rcu_is_watching(), |
||
934 | "rcu_read_unlock() used illegally while idle"); |
||
935 | rcu_lock_release(&rcu_lock_map); |
||
936 | __release(RCU); |
||
937 | __rcu_read_unlock(); |
||
938 | } |
||
939 | |||
940 | /** |
||
941 | * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section |
||
942 | * |
||
943 | * This is equivalent of rcu_read_lock(), but to be used when updates |
||
944 | * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since |
||
945 | * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a |
||
946 | * softirq handler to be a quiescent state, a process in RCU read-side |
||
947 | * critical section must be protected by disabling softirqs. Read-side |
||
948 | * critical sections in interrupt context can use just rcu_read_lock(), |
||
949 | * though this should at least be commented to avoid confusing people |
||
950 | * reading the code. |
||
951 | * |
||
952 | * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() |
||
953 | * must occur in the same context, for example, it is illegal to invoke |
||
954 | * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() |
||
955 | * was invoked from some other task. |
||
956 | */ |
||
957 | static inline void rcu_read_lock_bh(void) |
||
958 | { |
||
959 | local_bh_disable(); |
||
960 | __acquire(RCU_BH); |
||
961 | rcu_lock_acquire(&rcu_bh_lock_map); |
||
962 | rcu_lockdep_assert(rcu_is_watching(), |
||
963 | "rcu_read_lock_bh() used illegally while idle"); |
||
964 | } |
||
965 | |||
966 | /* |
||
967 | * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section |
||
968 | * |
||
969 | * See rcu_read_lock_bh() for more information. |
||
970 | */ |
||
971 | static inline void rcu_read_unlock_bh(void) |
||
972 | { |
||
973 | rcu_lockdep_assert(rcu_is_watching(), |
||
974 | "rcu_read_unlock_bh() used illegally while idle"); |
||
975 | rcu_lock_release(&rcu_bh_lock_map); |
||
976 | __release(RCU_BH); |
||
977 | local_bh_enable(); |
||
978 | } |
||
979 | |||
980 | /** |
||
981 | * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section |
||
982 | * |
||
983 | * This is equivalent of rcu_read_lock(), but to be used when updates |
||
984 | * are being done using call_rcu_sched() or synchronize_rcu_sched(). |
||
985 | * Read-side critical sections can also be introduced by anything that |
||
986 | * disables preemption, including local_irq_disable() and friends. |
||
987 | * |
||
988 | * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() |
||
989 | * must occur in the same context, for example, it is illegal to invoke |
||
990 | * rcu_read_unlock_sched() from process context if the matching |
||
991 | * rcu_read_lock_sched() was invoked from an NMI handler. |
||
992 | */ |
||
993 | static inline void rcu_read_lock_sched(void) |
||
994 | { |
||
995 | preempt_disable(); |
||
996 | __acquire(RCU_SCHED); |
||
997 | rcu_lock_acquire(&rcu_sched_lock_map); |
||
998 | rcu_lockdep_assert(rcu_is_watching(), |
||
999 | "rcu_read_lock_sched() used illegally while idle"); |
||
1000 | } |
||
1001 | |||
1002 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
||
1003 | static inline notrace void rcu_read_lock_sched_notrace(void) |
||
1004 | { |
||
1005 | preempt_disable_notrace(); |
||
1006 | __acquire(RCU_SCHED); |
||
1007 | } |
||
1008 | |||
1009 | /* |
||
1010 | * rcu_read_unlock_sched - marks the end of a RCU-classic critical section |
||
1011 | * |
||
1012 | * See rcu_read_lock_sched for more information. |
||
1013 | */ |
||
1014 | static inline void rcu_read_unlock_sched(void) |
||
1015 | { |
||
1016 | rcu_lockdep_assert(rcu_is_watching(), |
||
1017 | "rcu_read_unlock_sched() used illegally while idle"); |
||
1018 | rcu_lock_release(&rcu_sched_lock_map); |
||
1019 | __release(RCU_SCHED); |
||
1020 | preempt_enable(); |
||
1021 | } |
||
1022 | |||
1023 | /* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ |
||
1024 | static inline notrace void rcu_read_unlock_sched_notrace(void) |
||
1025 | { |
||
1026 | __release(RCU_SCHED); |
||
1027 | preempt_enable_notrace(); |
||
1028 | } |
||
1029 | |||
1030 | /** |
||
1031 | * RCU_INIT_POINTER() - initialize an RCU protected pointer |
||
1032 | * |
||
1033 | * Initialize an RCU-protected pointer in special cases where readers |
||
1034 | * do not need ordering constraints on the CPU or the compiler. These |
||
1035 | * special cases are: |
||
1036 | * |
||
1037 | * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- |
||
1038 | * 2. The caller has taken whatever steps are required to prevent |
||
1039 | * RCU readers from concurrently accessing this pointer -or- |
||
1040 | * 3. The referenced data structure has already been exposed to |
||
1041 | * readers either at compile time or via rcu_assign_pointer() -and- |
||
1042 | * a. You have not made -any- reader-visible changes to |
||
1043 | * this structure since then -or- |
||
1044 | * b. It is OK for readers accessing this structure from its |
||
1045 | * new location to see the old state of the structure. (For |
||
1046 | * example, the changes were to statistical counters or to |
||
1047 | * other state where exact synchronization is not required.) |
||
1048 | * |
||
1049 | * Failure to follow these rules governing use of RCU_INIT_POINTER() will |
||
1050 | * result in impossible-to-diagnose memory corruption. As in the structures |
||
1051 | * will look OK in crash dumps, but any concurrent RCU readers might |
||
1052 | * see pre-initialized values of the referenced data structure. So |
||
1053 | * please be very careful how you use RCU_INIT_POINTER()!!! |
||
1054 | * |
||
1055 | * If you are creating an RCU-protected linked structure that is accessed |
||
1056 | * by a single external-to-structure RCU-protected pointer, then you may |
||
1057 | * use RCU_INIT_POINTER() to initialize the internal RCU-protected |
||
1058 | * pointers, but you must use rcu_assign_pointer() to initialize the |
||
1059 | * external-to-structure pointer -after- you have completely initialized |
||
1060 | * the reader-accessible portions of the linked structure. |
||
1061 | * |
||
1062 | * Note that unlike rcu_assign_pointer(), RCU_INIT_POINTER() provides no |
||
1063 | * ordering guarantees for either the CPU or the compiler. |
||
1064 | */ |
||
1065 | #define RCU_INIT_POINTER(p, v) \ |
||
1066 | do { \ |
||
1067 | rcu_dereference_sparse(p, __rcu); \ |
||
1068 | p = RCU_INITIALIZER(v); \ |
||
1069 | } while (0) |
||
1070 | |||
1071 | /** |
||
1072 | * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer |
||
1073 | * |
||
1074 | * GCC-style initialization for an RCU-protected pointer in a structure field. |
||
1075 | */ |
||
1076 | #define RCU_POINTER_INITIALIZER(p, v) \ |
||
1077 | .p = RCU_INITIALIZER(v) |
||
1078 | |||
1079 | /* |
||
1080 | * Does the specified offset indicate that the corresponding rcu_head |
||
1081 | * structure can be handled by kfree_rcu()? |
||
1082 | */ |
||
1083 | #define __is_kfree_rcu_offset(offset) ((offset) < 4096) |
||
1084 | |||
1085 | /* |
||
1086 | * Helper macro for kfree_rcu() to prevent argument-expansion eyestrain. |
||
1087 | */ |
||
1088 | #define __kfree_rcu(head, offset) \ |
||
1089 | do { \ |
||
1090 | BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); \ |
||
1091 | kfree_call_rcu(head, (void (*)(struct rcu_head *))(unsigned long)(offset)); \ |
||
1092 | } while (0) |
||
1093 | |||
1094 | /** |
||
1095 | * kfree_rcu() - kfree an object after a grace period. |
||
1096 | * @ptr: pointer to kfree |
||
1097 | * @rcu_head: the name of the struct rcu_head within the type of @ptr. |
||
1098 | * |
||
1099 | * Many rcu callbacks functions just call kfree() on the base structure. |
||
1100 | * These functions are trivial, but their size adds up, and furthermore |
||
1101 | * when they are used in a kernel module, that module must invoke the |
||
1102 | * high-latency rcu_barrier() function at module-unload time. |
||
1103 | * |
||
1104 | * The kfree_rcu() function handles this issue. Rather than encoding a |
||
1105 | * function address in the embedded rcu_head structure, kfree_rcu() instead |
||
1106 | * encodes the offset of the rcu_head structure within the base structure. |
||
1107 | * Because the functions are not allowed in the low-order 4096 bytes of |
||
1108 | * kernel virtual memory, offsets up to 4095 bytes can be accommodated. |
||
1109 | * If the offset is larger than 4095 bytes, a compile-time error will |
||
1110 | * be generated in __kfree_rcu(). If this error is triggered, you can |
||
1111 | * either fall back to use of call_rcu() or rearrange the structure to |
||
1112 | * position the rcu_head structure into the first 4096 bytes. |
||
1113 | * |
||
1114 | * Note that the allowable offset might decrease in the future, for example, |
||
1115 | * to allow something like kmem_cache_free_rcu(). |
||
1116 | * |
||
1117 | * The BUILD_BUG_ON check must not involve any function calls, hence the |
||
1118 | * checks are done in macros here. |
||
1119 | */ |
||
1120 | #define kfree_rcu(ptr, rcu_head) \ |
||
1121 | __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) |
||
1122 | |||
1123 | #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) |
||
1124 | static inline int rcu_needs_cpu(unsigned long *delta_jiffies) |
||
1125 | { |
||
1126 | *delta_jiffies = ULONG_MAX; |
||
1127 | return 0; |
||
1128 | } |
||
1129 | #endif /* #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) */ |
||
1130 | |||
1131 | #if defined(CONFIG_RCU_NOCB_CPU_ALL) |
||
1132 | static inline bool rcu_is_nocb_cpu(int cpu) { return true; } |
||
1133 | #elif defined(CONFIG_RCU_NOCB_CPU) |
||
1134 | bool rcu_is_nocb_cpu(int cpu); |
||
1135 | #else |
||
1136 | static inline bool rcu_is_nocb_cpu(int cpu) { return false; } |
||
1137 | #endif |
||
1138 | |||
1139 | |||
1140 | /* Only for use by adaptive-ticks code. */ |
||
1141 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
||
1142 | bool rcu_sys_is_idle(void); |
||
1143 | void rcu_sysidle_force_exit(void); |
||
1144 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
||
1145 | |||
1146 | static inline bool rcu_sys_is_idle(void) |
||
1147 | { |
||
1148 | return false; |
||
1149 | } |
||
1150 | |||
1151 | static inline void rcu_sysidle_force_exit(void) |
||
1152 | { |
||
1153 | } |
||
1154 | |||
1155 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
||
1156 | |||
1157 | |||
1158 | #endif /* __LINUX_RCUPDATE_H */>>> |