kernel/rcu/rcu.h

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