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Linux/kernel/rcu/rcu.h

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  1 /*
  2  * Read-Copy Update definitions shared among RCU implementations.
  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, 2011
 19  *
 20  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 21  */
 22 
 23 #ifndef __LINUX_RCU_H
 24 #define __LINUX_RCU_H
 25 
 26 #include <trace/events/rcu.h>
 27 #ifdef CONFIG_RCU_TRACE
 28 #define RCU_TRACE(stmt) stmt
 29 #else /* #ifdef CONFIG_RCU_TRACE */
 30 #define RCU_TRACE(stmt)
 31 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 32 
 33 /* Offset to allow for unmatched rcu_irq_{enter,exit}(). */
 34 #define DYNTICK_IRQ_NONIDLE     ((LONG_MAX / 2) + 1)
 35 
 36 
 37 /*
 38  * Grace-period counter management.
 39  */
 40 
 41 #define RCU_SEQ_CTR_SHIFT       2
 42 #define RCU_SEQ_STATE_MASK      ((1 << RCU_SEQ_CTR_SHIFT) - 1)
 43 
 44 /*
 45  * Return the counter portion of a sequence number previously returned
 46  * by rcu_seq_snap() or rcu_seq_current().
 47  */
 48 static inline unsigned long rcu_seq_ctr(unsigned long s)
 49 {
 50         return s >> RCU_SEQ_CTR_SHIFT;
 51 }
 52 
 53 /*
 54  * Return the state portion of a sequence number previously returned
 55  * by rcu_seq_snap() or rcu_seq_current().
 56  */
 57 static inline int rcu_seq_state(unsigned long s)
 58 {
 59         return s & RCU_SEQ_STATE_MASK;
 60 }
 61 
 62 /*
 63  * Set the state portion of the pointed-to sequence number.
 64  * The caller is responsible for preventing conflicting updates.
 65  */
 66 static inline void rcu_seq_set_state(unsigned long *sp, int newstate)
 67 {
 68         WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK);
 69         WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate);
 70 }
 71 
 72 /* Adjust sequence number for start of update-side operation. */
 73 static inline void rcu_seq_start(unsigned long *sp)
 74 {
 75         WRITE_ONCE(*sp, *sp + 1);
 76         smp_mb(); /* Ensure update-side operation after counter increment. */
 77         WARN_ON_ONCE(rcu_seq_state(*sp) != 1);
 78 }
 79 
 80 /* Compute the end-of-grace-period value for the specified sequence number. */
 81 static inline unsigned long rcu_seq_endval(unsigned long *sp)
 82 {
 83         return (*sp | RCU_SEQ_STATE_MASK) + 1;
 84 }
 85 
 86 /* Adjust sequence number for end of update-side operation. */
 87 static inline void rcu_seq_end(unsigned long *sp)
 88 {
 89         smp_mb(); /* Ensure update-side operation before counter increment. */
 90         WARN_ON_ONCE(!rcu_seq_state(*sp));
 91         WRITE_ONCE(*sp, rcu_seq_endval(sp));
 92 }
 93 
 94 /* Take a snapshot of the update side's sequence number. */
 95 static inline unsigned long rcu_seq_snap(unsigned long *sp)
 96 {
 97         unsigned long s;
 98 
 99         s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK;
100         smp_mb(); /* Above access must not bleed into critical section. */
101         return s;
102 }
103 
104 /* Return the current value the update side's sequence number, no ordering. */
105 static inline unsigned long rcu_seq_current(unsigned long *sp)
106 {
107         return READ_ONCE(*sp);
108 }
109 
110 /*
111  * Given a snapshot from rcu_seq_snap(), determine whether or not a
112  * full update-side operation has occurred.
113  */
114 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
115 {
116         return ULONG_CMP_GE(READ_ONCE(*sp), s);
117 }
118 
119 /*
120  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
121  * by call_rcu() and rcu callback execution, and are therefore not part of the
122  * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
123  */
124 
125 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
126 # define STATE_RCU_HEAD_READY   0
127 # define STATE_RCU_HEAD_QUEUED  1
128 
129 extern struct debug_obj_descr rcuhead_debug_descr;
130 
131 static inline int debug_rcu_head_queue(struct rcu_head *head)
132 {
133         int r1;
134 
135         r1 = debug_object_activate(head, &rcuhead_debug_descr);
136         debug_object_active_state(head, &rcuhead_debug_descr,
137                                   STATE_RCU_HEAD_READY,
138                                   STATE_RCU_HEAD_QUEUED);
139         return r1;
140 }
141 
142 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
143 {
144         debug_object_active_state(head, &rcuhead_debug_descr,
145                                   STATE_RCU_HEAD_QUEUED,
146                                   STATE_RCU_HEAD_READY);
147         debug_object_deactivate(head, &rcuhead_debug_descr);
148 }
149 #else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
150 static inline int debug_rcu_head_queue(struct rcu_head *head)
151 {
152         return 0;
153 }
154 
155 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
156 {
157 }
158 #endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
159 
160 void kfree(const void *);
161 
162 /*
163  * Reclaim the specified callback, either by invoking it (non-lazy case)
164  * or freeing it directly (lazy case).  Return true if lazy, false otherwise.
165  */
166 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
167 {
168         unsigned long offset = (unsigned long)head->func;
169 
170         rcu_lock_acquire(&rcu_callback_map);
171         if (__is_kfree_rcu_offset(offset)) {
172                 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
173                 kfree((void *)head - offset);
174                 rcu_lock_release(&rcu_callback_map);
175                 return true;
176         } else {
177                 RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
178                 head->func(head);
179                 rcu_lock_release(&rcu_callback_map);
180                 return false;
181         }
182 }
183 
184 #ifdef CONFIG_RCU_STALL_COMMON
185 
186 extern int rcu_cpu_stall_suppress;
187 int rcu_jiffies_till_stall_check(void);
188 
189 #define rcu_ftrace_dump_stall_suppress() \
190 do { \
191         if (!rcu_cpu_stall_suppress) \
192                 rcu_cpu_stall_suppress = 3; \
193 } while (0)
194 
195 #define rcu_ftrace_dump_stall_unsuppress() \
196 do { \
197         if (rcu_cpu_stall_suppress == 3) \
198                 rcu_cpu_stall_suppress = 0; \
199 } while (0)
200 
201 #else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */
202 #define rcu_ftrace_dump_stall_suppress()
203 #define rcu_ftrace_dump_stall_unsuppress()
204 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
205 
206 /*
207  * Strings used in tracepoints need to be exported via the
208  * tracing system such that tools like perf and trace-cmd can
209  * translate the string address pointers to actual text.
210  */
211 #define TPS(x)  tracepoint_string(x)
212 
213 /*
214  * Dump the ftrace buffer, but only one time per callsite per boot.
215  */
216 #define rcu_ftrace_dump(oops_dump_mode) \
217 do { \
218         static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
219         \
220         if (!atomic_read(&___rfd_beenhere) && \
221             !atomic_xchg(&___rfd_beenhere, 1)) { \
222                 tracing_off(); \
223                 rcu_ftrace_dump_stall_suppress(); \
224                 ftrace_dump(oops_dump_mode); \
225                 rcu_ftrace_dump_stall_unsuppress(); \
226         } \
227 } while (0)
228 
229 void rcu_early_boot_tests(void);
230 void rcu_test_sync_prims(void);
231 
232 /*
233  * This function really isn't for public consumption, but RCU is special in
234  * that context switches can allow the state machine to make progress.
235  */
236 extern void resched_cpu(int cpu);
237 
238 #if defined(SRCU) || !defined(TINY_RCU)
239 
240 #include <linux/rcu_node_tree.h>
241 
242 extern int rcu_num_lvls;
243 extern int num_rcu_lvl[];
244 extern int rcu_num_nodes;
245 static bool rcu_fanout_exact;
246 static int rcu_fanout_leaf;
247 
248 /*
249  * Compute the per-level fanout, either using the exact fanout specified
250  * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
251  */
252 static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
253 {
254         int i;
255 
256         if (rcu_fanout_exact) {
257                 levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
258                 for (i = rcu_num_lvls - 2; i >= 0; i--)
259                         levelspread[i] = RCU_FANOUT;
260         } else {
261                 int ccur;
262                 int cprv;
263 
264                 cprv = nr_cpu_ids;
265                 for (i = rcu_num_lvls - 1; i >= 0; i--) {
266                         ccur = levelcnt[i];
267                         levelspread[i] = (cprv + ccur - 1) / ccur;
268                         cprv = ccur;
269                 }
270         }
271 }
272 
273 /* Returns first leaf rcu_node of the specified RCU flavor. */
274 #define rcu_first_leaf_node(rsp) ((rsp)->level[rcu_num_lvls - 1])
275 
276 /* Is this rcu_node a leaf? */
277 #define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)
278 
279 /*
280  * Do a full breadth-first scan of the rcu_node structures for the
281  * specified rcu_state structure.
282  */
283 #define rcu_for_each_node_breadth_first(rsp, rnp) \
284         for ((rnp) = &(rsp)->node[0]; \
285              (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
286 
287 /*
288  * Do a breadth-first scan of the non-leaf rcu_node structures for the
289  * specified rcu_state structure.  Note that if there is a singleton
290  * rcu_node tree with but one rcu_node structure, this loop is a no-op.
291  */
292 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
293         for ((rnp) = &(rsp)->node[0]; !rcu_is_leaf_node(rsp, rnp); (rnp)++)
294 
295 /*
296  * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
297  * structure.  Note that if there is a singleton rcu_node tree with but
298  * one rcu_node structure, this loop -will- visit the rcu_node structure.
299  * It is still a leaf node, even if it is also the root node.
300  */
301 #define rcu_for_each_leaf_node(rsp, rnp) \
302         for ((rnp) = rcu_first_leaf_node(rsp); \
303              (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
304 
305 /*
306  * Iterate over all possible CPUs in a leaf RCU node.
307  */
308 #define for_each_leaf_node_possible_cpu(rnp, cpu) \
309         for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
310              (cpu) <= rnp->grphi; \
311              (cpu) = cpumask_next((cpu), cpu_possible_mask))
312 
313 /*
314  * Iterate over all CPUs in a leaf RCU node's specified mask.
315  */
316 #define rcu_find_next_bit(rnp, cpu, mask) \
317         ((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
318 #define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
319         for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
320              (cpu) <= rnp->grphi; \
321              (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
322 
323 /*
324  * Wrappers for the rcu_node::lock acquire and release.
325  *
326  * Because the rcu_nodes form a tree, the tree traversal locking will observe
327  * different lock values, this in turn means that an UNLOCK of one level
328  * followed by a LOCK of another level does not imply a full memory barrier;
329  * and most importantly transitivity is lost.
330  *
331  * In order to restore full ordering between tree levels, augment the regular
332  * lock acquire functions with smp_mb__after_unlock_lock().
333  *
334  * As ->lock of struct rcu_node is a __private field, therefore one should use
335  * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
336  */
337 #define raw_spin_lock_rcu_node(p)                                       \
338 do {                                                                    \
339         raw_spin_lock(&ACCESS_PRIVATE(p, lock));                        \
340         smp_mb__after_unlock_lock();                                    \
341 } while (0)
342 
343 #define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock))
344 
345 #define raw_spin_lock_irq_rcu_node(p)                                   \
346 do {                                                                    \
347         raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock));                    \
348         smp_mb__after_unlock_lock();                                    \
349 } while (0)
350 
351 #define raw_spin_unlock_irq_rcu_node(p)                                 \
352         raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock))
353 
354 #define raw_spin_lock_irqsave_rcu_node(p, flags)                        \
355 do {                                                                    \
356         raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
357         smp_mb__after_unlock_lock();                                    \
358 } while (0)
359 
360 #define raw_spin_unlock_irqrestore_rcu_node(p, flags)                   \
361         raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)
362 
363 #define raw_spin_trylock_rcu_node(p)                                    \
364 ({                                                                      \
365         bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock));    \
366                                                                         \
367         if (___locked)                                                  \
368                 smp_mb__after_unlock_lock();                            \
369         ___locked;                                                      \
370 })
371 
372 #define raw_lockdep_assert_held_rcu_node(p)                             \
373         lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
374 
375 #endif /* #if defined(SRCU) || !defined(TINY_RCU) */
376 
377 #ifdef CONFIG_TINY_RCU
378 /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
379 static inline bool rcu_gp_is_normal(void) { return true; }
380 static inline bool rcu_gp_is_expedited(void) { return false; }
381 static inline void rcu_expedite_gp(void) { }
382 static inline void rcu_unexpedite_gp(void) { }
383 static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }
384 #else /* #ifdef CONFIG_TINY_RCU */
385 bool rcu_gp_is_normal(void);     /* Internal RCU use. */
386 bool rcu_gp_is_expedited(void);  /* Internal RCU use. */
387 void rcu_expedite_gp(void);
388 void rcu_unexpedite_gp(void);
389 void rcupdate_announce_bootup_oddness(void);
390 void rcu_request_urgent_qs_task(struct task_struct *t);
391 #endif /* #else #ifdef CONFIG_TINY_RCU */
392 
393 #define RCU_SCHEDULER_INACTIVE  0
394 #define RCU_SCHEDULER_INIT      1
395 #define RCU_SCHEDULER_RUNNING   2
396 
397 enum rcutorture_type {
398         RCU_FLAVOR,
399         RCU_BH_FLAVOR,
400         RCU_SCHED_FLAVOR,
401         RCU_TASKS_FLAVOR,
402         SRCU_FLAVOR,
403         INVALID_RCU_FLAVOR
404 };
405 
406 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
407 void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
408                             unsigned long *gpnum, unsigned long *completed);
409 void rcutorture_record_test_transition(void);
410 void rcutorture_record_progress(unsigned long vernum);
411 void do_trace_rcu_torture_read(const char *rcutorturename,
412                                struct rcu_head *rhp,
413                                unsigned long secs,
414                                unsigned long c_old,
415                                unsigned long c);
416 #else
417 static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
418                                           int *flags,
419                                           unsigned long *gpnum,
420                                           unsigned long *completed)
421 {
422         *flags = 0;
423         *gpnum = 0;
424         *completed = 0;
425 }
426 static inline void rcutorture_record_test_transition(void) { }
427 static inline void rcutorture_record_progress(unsigned long vernum) { }
428 #ifdef CONFIG_RCU_TRACE
429 void do_trace_rcu_torture_read(const char *rcutorturename,
430                                struct rcu_head *rhp,
431                                unsigned long secs,
432                                unsigned long c_old,
433                                unsigned long c);
434 #else
435 #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
436         do { } while (0)
437 #endif
438 #endif
439 
440 #ifdef CONFIG_TINY_SRCU
441 
442 static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
443                                            struct srcu_struct *sp, int *flags,
444                                            unsigned long *gpnum,
445                                            unsigned long *completed)
446 {
447         if (test_type != SRCU_FLAVOR)
448                 return;
449         *flags = 0;
450         *completed = sp->srcu_idx;
451         *gpnum = *completed;
452 }
453 
454 #elif defined(CONFIG_TREE_SRCU)
455 
456 void srcutorture_get_gp_data(enum rcutorture_type test_type,
457                              struct srcu_struct *sp, int *flags,
458                              unsigned long *gpnum, unsigned long *completed);
459 
460 #endif
461 
462 #ifdef CONFIG_TINY_RCU
463 static inline unsigned long rcu_batches_started(void) { return 0; }
464 static inline unsigned long rcu_batches_started_bh(void) { return 0; }
465 static inline unsigned long rcu_batches_started_sched(void) { return 0; }
466 static inline unsigned long rcu_batches_completed(void) { return 0; }
467 static inline unsigned long rcu_batches_completed_bh(void) { return 0; }
468 static inline unsigned long rcu_batches_completed_sched(void) { return 0; }
469 static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
470 static inline unsigned long rcu_exp_batches_completed_sched(void) { return 0; }
471 static inline unsigned long
472 srcu_batches_completed(struct srcu_struct *sp) { return 0; }
473 static inline void rcu_force_quiescent_state(void) { }
474 static inline void rcu_bh_force_quiescent_state(void) { }
475 static inline void rcu_sched_force_quiescent_state(void) { }
476 static inline void show_rcu_gp_kthreads(void) { }
477 #else /* #ifdef CONFIG_TINY_RCU */
478 extern unsigned long rcutorture_testseq;
479 extern unsigned long rcutorture_vernum;
480 unsigned long rcu_batches_started(void);
481 unsigned long rcu_batches_started_bh(void);
482 unsigned long rcu_batches_started_sched(void);
483 unsigned long rcu_batches_completed(void);
484 unsigned long rcu_batches_completed_bh(void);
485 unsigned long rcu_batches_completed_sched(void);
486 unsigned long rcu_exp_batches_completed(void);
487 unsigned long rcu_exp_batches_completed_sched(void);
488 unsigned long srcu_batches_completed(struct srcu_struct *sp);
489 void show_rcu_gp_kthreads(void);
490 void rcu_force_quiescent_state(void);
491 void rcu_bh_force_quiescent_state(void);
492 void rcu_sched_force_quiescent_state(void);
493 extern struct workqueue_struct *rcu_gp_wq;
494 extern struct workqueue_struct *rcu_par_gp_wq;
495 #endif /* #else #ifdef CONFIG_TINY_RCU */
496 
497 #ifdef CONFIG_RCU_NOCB_CPU
498 bool rcu_is_nocb_cpu(int cpu);
499 #else
500 static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
501 #endif
502 
503 #endif /* __LINUX_RCU_H */
504 

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