1 /* 2 * Read-Copy Update mechanism for mutual exclusion (tree-based version) 3 * Internal non-public definitions. 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, you can access it online at 17 * http://www.gnu.org/licenses/gpl-2.0.html. 18 * 19 * Copyright IBM Corporation, 2008 20 * 21 * Author: Ingo Molnar <mingo@elte.hu> 22 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> 23 */ 24 25 #include <linux/cache.h> 26 #include <linux/spinlock.h> 27 #include <linux/threads.h> 28 #include <linux/cpumask.h> 29 #include <linux/seqlock.h> 30 #include <linux/stop_machine.h> 31 32 /* 33 * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and 34 * CONFIG_RCU_FANOUT_LEAF. 35 * In theory, it should be possible to add more levels straightforwardly. 36 * In practice, this did work well going from three levels to four. 37 * Of course, your mileage may vary. 38 */ 39 40 #ifdef CONFIG_RCU_FANOUT 41 #define RCU_FANOUT CONFIG_RCU_FANOUT 42 #else /* #ifdef CONFIG_RCU_FANOUT */ 43 # ifdef CONFIG_64BIT 44 # define RCU_FANOUT 64 45 # else 46 # define RCU_FANOUT 32 47 # endif 48 #endif /* #else #ifdef CONFIG_RCU_FANOUT */ 49 50 #ifdef CONFIG_RCU_FANOUT_LEAF 51 #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF 52 #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ 53 # ifdef CONFIG_64BIT 54 # define RCU_FANOUT_LEAF 64 55 # else 56 # define RCU_FANOUT_LEAF 32 57 # endif 58 #endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */ 59 60 #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) 61 #define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT) 62 #define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT) 63 #define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT) 64 65 #if NR_CPUS <= RCU_FANOUT_1 66 # define RCU_NUM_LVLS 1 67 # define NUM_RCU_LVL_0 1 68 # define NUM_RCU_NODES NUM_RCU_LVL_0 69 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 } 70 # define RCU_NODE_NAME_INIT { "rcu_node_0" } 71 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" } 72 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0" } 73 # define RCU_EXP_SCHED_NAME_INIT \ 74 { "rcu_node_exp_sched_0" } 75 #elif NR_CPUS <= RCU_FANOUT_2 76 # define RCU_NUM_LVLS 2 77 # define NUM_RCU_LVL_0 1 78 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 79 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1) 80 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 } 81 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" } 82 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" } 83 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" } 84 # define RCU_EXP_SCHED_NAME_INIT \ 85 { "rcu_node_exp_sched_0", "rcu_node_exp_sched_1" } 86 #elif NR_CPUS <= RCU_FANOUT_3 87 # define RCU_NUM_LVLS 3 88 # define NUM_RCU_LVL_0 1 89 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) 90 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 91 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2) 92 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 } 93 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" } 94 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" } 95 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" } 96 # define RCU_EXP_SCHED_NAME_INIT \ 97 { "rcu_node_exp_sched_0", "rcu_node_exp_sched_1", "rcu_node_exp_sched_2" } 98 #elif NR_CPUS <= RCU_FANOUT_4 99 # define RCU_NUM_LVLS 4 100 # define NUM_RCU_LVL_0 1 101 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) 102 # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) 103 # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 104 # define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) 105 # define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 } 106 # define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" } 107 # define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" } 108 # define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" } 109 # define RCU_EXP_SCHED_NAME_INIT \ 110 { "rcu_node_exp_sched_0", "rcu_node_exp_sched_1", "rcu_node_exp_sched_2", "rcu_node_exp_sched_3" } 111 #else 112 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" 113 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ 114 115 extern int rcu_num_lvls; 116 extern int rcu_num_nodes; 117 118 /* 119 * Dynticks per-CPU state. 120 */ 121 struct rcu_dynticks { 122 long long dynticks_nesting; /* Track irq/process nesting level. */ 123 /* Process level is worth LLONG_MAX/2. */ 124 int dynticks_nmi_nesting; /* Track NMI nesting level. */ 125 atomic_t dynticks; /* Even value for idle, else odd. */ 126 #ifdef CONFIG_NO_HZ_FULL_SYSIDLE 127 long long dynticks_idle_nesting; 128 /* irq/process nesting level from idle. */ 129 atomic_t dynticks_idle; /* Even value for idle, else odd. */ 130 /* "Idle" excludes userspace execution. */ 131 unsigned long dynticks_idle_jiffies; 132 /* End of last non-NMI non-idle period. */ 133 #endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ 134 #ifdef CONFIG_RCU_FAST_NO_HZ 135 bool all_lazy; /* Are all CPU's CBs lazy? */ 136 unsigned long nonlazy_posted; 137 /* # times non-lazy CBs posted to CPU. */ 138 unsigned long nonlazy_posted_snap; 139 /* idle-period nonlazy_posted snapshot. */ 140 unsigned long last_accelerate; 141 /* Last jiffy CBs were accelerated. */ 142 unsigned long last_advance_all; 143 /* Last jiffy CBs were all advanced. */ 144 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ 145 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ 146 }; 147 148 /* RCU's kthread states for tracing. */ 149 #define RCU_KTHREAD_STOPPED 0 150 #define RCU_KTHREAD_RUNNING 1 151 #define RCU_KTHREAD_WAITING 2 152 #define RCU_KTHREAD_OFFCPU 3 153 #define RCU_KTHREAD_YIELDING 4 154 #define RCU_KTHREAD_MAX 4 155 156 /* 157 * Definition for node within the RCU grace-period-detection hierarchy. 158 */ 159 struct rcu_node { 160 raw_spinlock_t lock; /* Root rcu_node's lock protects some */ 161 /* rcu_state fields as well as following. */ 162 unsigned long gpnum; /* Current grace period for this node. */ 163 /* This will either be equal to or one */ 164 /* behind the root rcu_node's gpnum. */ 165 unsigned long completed; /* Last GP completed for this node. */ 166 /* This will either be equal to or one */ 167 /* behind the root rcu_node's gpnum. */ 168 unsigned long qsmask; /* CPUs or groups that need to switch in */ 169 /* order for current grace period to proceed.*/ 170 /* In leaf rcu_node, each bit corresponds to */ 171 /* an rcu_data structure, otherwise, each */ 172 /* bit corresponds to a child rcu_node */ 173 /* structure. */ 174 unsigned long expmask; /* Groups that have ->blkd_tasks */ 175 /* elements that need to drain to allow the */ 176 /* current expedited grace period to */ 177 /* complete (only for PREEMPT_RCU). */ 178 unsigned long qsmaskinit; 179 /* Per-GP initial value for qsmask & expmask. */ 180 /* Initialized from ->qsmaskinitnext at the */ 181 /* beginning of each grace period. */ 182 unsigned long qsmaskinitnext; 183 /* Online CPUs for next grace period. */ 184 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 185 /* Only one bit will be set in this mask. */ 186 int grplo; /* lowest-numbered CPU or group here. */ 187 int grphi; /* highest-numbered CPU or group here. */ 188 u8 grpnum; /* CPU/group number for next level up. */ 189 u8 level; /* root is at level 0. */ 190 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ 191 /* exit RCU read-side critical sections */ 192 /* before propagating offline up the */ 193 /* rcu_node tree? */ 194 struct rcu_node *parent; 195 struct list_head blkd_tasks; 196 /* Tasks blocked in RCU read-side critical */ 197 /* section. Tasks are placed at the head */ 198 /* of this list and age towards the tail. */ 199 struct list_head *gp_tasks; 200 /* Pointer to the first task blocking the */ 201 /* current grace period, or NULL if there */ 202 /* is no such task. */ 203 struct list_head *exp_tasks; 204 /* Pointer to the first task blocking the */ 205 /* current expedited grace period, or NULL */ 206 /* if there is no such task. If there */ 207 /* is no current expedited grace period, */ 208 /* then there can cannot be any such task. */ 209 struct list_head *boost_tasks; 210 /* Pointer to first task that needs to be */ 211 /* priority boosted, or NULL if no priority */ 212 /* boosting is needed for this rcu_node */ 213 /* structure. If there are no tasks */ 214 /* queued on this rcu_node structure that */ 215 /* are blocking the current grace period, */ 216 /* there can be no such task. */ 217 struct rt_mutex boost_mtx; 218 /* Used only for the priority-boosting */ 219 /* side effect, not as a lock. */ 220 unsigned long boost_time; 221 /* When to start boosting (jiffies). */ 222 struct task_struct *boost_kthread_task; 223 /* kthread that takes care of priority */ 224 /* boosting for this rcu_node structure. */ 225 unsigned int boost_kthread_status; 226 /* State of boost_kthread_task for tracing. */ 227 unsigned long n_tasks_boosted; 228 /* Total number of tasks boosted. */ 229 unsigned long n_exp_boosts; 230 /* Number of tasks boosted for expedited GP. */ 231 unsigned long n_normal_boosts; 232 /* Number of tasks boosted for normal GP. */ 233 unsigned long n_balk_blkd_tasks; 234 /* Refused to boost: no blocked tasks. */ 235 unsigned long n_balk_exp_gp_tasks; 236 /* Refused to boost: nothing blocking GP. */ 237 unsigned long n_balk_boost_tasks; 238 /* Refused to boost: already boosting. */ 239 unsigned long n_balk_notblocked; 240 /* Refused to boost: RCU RS CS still running. */ 241 unsigned long n_balk_notyet; 242 /* Refused to boost: not yet time. */ 243 unsigned long n_balk_nos; 244 /* Refused to boost: not sure why, though. */ 245 /* This can happen due to race conditions. */ 246 #ifdef CONFIG_RCU_NOCB_CPU 247 wait_queue_head_t nocb_gp_wq[2]; 248 /* Place for rcu_nocb_kthread() to wait GP. */ 249 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 250 int need_future_gp[2]; 251 /* Counts of upcoming no-CB GP requests. */ 252 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; 253 254 struct mutex exp_funnel_mutex ____cacheline_internodealigned_in_smp; 255 } ____cacheline_internodealigned_in_smp; 256 257 /* 258 * Do a full breadth-first scan of the rcu_node structures for the 259 * specified rcu_state structure. 260 */ 261 #define rcu_for_each_node_breadth_first(rsp, rnp) \ 262 for ((rnp) = &(rsp)->node[0]; \ 263 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) 264 265 /* 266 * Do a breadth-first scan of the non-leaf rcu_node structures for the 267 * specified rcu_state structure. Note that if there is a singleton 268 * rcu_node tree with but one rcu_node structure, this loop is a no-op. 269 */ 270 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ 271 for ((rnp) = &(rsp)->node[0]; \ 272 (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++) 273 274 /* 275 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state 276 * structure. Note that if there is a singleton rcu_node tree with but 277 * one rcu_node structure, this loop -will- visit the rcu_node structure. 278 * It is still a leaf node, even if it is also the root node. 279 */ 280 #define rcu_for_each_leaf_node(rsp, rnp) \ 281 for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \ 282 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) 283 284 /* Index values for nxttail array in struct rcu_data. */ 285 #define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ 286 #define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ 287 #define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ 288 #define RCU_NEXT_TAIL 3 289 #define RCU_NEXT_SIZE 4 290 291 /* Per-CPU data for read-copy update. */ 292 struct rcu_data { 293 /* 1) quiescent-state and grace-period handling : */ 294 unsigned long completed; /* Track rsp->completed gp number */ 295 /* in order to detect GP end. */ 296 unsigned long gpnum; /* Highest gp number that this CPU */ 297 /* is aware of having started. */ 298 unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */ 299 /* for rcu_all_qs() invocations. */ 300 bool passed_quiesce; /* User-mode/idle loop etc. */ 301 bool qs_pending; /* Core waits for quiesc state. */ 302 bool beenonline; /* CPU online at least once. */ 303 bool gpwrap; /* Possible gpnum/completed wrap. */ 304 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 305 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 306 unsigned long ticks_this_gp; /* The number of scheduling-clock */ 307 /* ticks this CPU has handled */ 308 /* during and after the last grace */ 309 /* period it is aware of. */ 310 struct cpu_stop_work exp_stop_work; 311 /* Expedited grace-period control */ 312 /* for CPU stopping. */ 313 314 /* 2) batch handling */ 315 /* 316 * If nxtlist is not NULL, it is partitioned as follows. 317 * Any of the partitions might be empty, in which case the 318 * pointer to that partition will be equal to the pointer for 319 * the following partition. When the list is empty, all of 320 * the nxttail elements point to the ->nxtlist pointer itself, 321 * which in that case is NULL. 322 * 323 * [nxtlist, *nxttail[RCU_DONE_TAIL]): 324 * Entries that batch # <= ->completed 325 * The grace period for these entries has completed, and 326 * the other grace-period-completed entries may be moved 327 * here temporarily in rcu_process_callbacks(). 328 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): 329 * Entries that batch # <= ->completed - 1: waiting for current GP 330 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): 331 * Entries known to have arrived before current GP ended 332 * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]): 333 * Entries that might have arrived after current GP ended 334 * Note that the value of *nxttail[RCU_NEXT_TAIL] will 335 * always be NULL, as this is the end of the list. 336 */ 337 struct rcu_head *nxtlist; 338 struct rcu_head **nxttail[RCU_NEXT_SIZE]; 339 unsigned long nxtcompleted[RCU_NEXT_SIZE]; 340 /* grace periods for sublists. */ 341 long qlen_lazy; /* # of lazy queued callbacks */ 342 long qlen; /* # of queued callbacks, incl lazy */ 343 long qlen_last_fqs_check; 344 /* qlen at last check for QS forcing */ 345 unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */ 346 unsigned long n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */ 347 unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */ 348 unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */ 349 unsigned long n_force_qs_snap; 350 /* did other CPU force QS recently? */ 351 long blimit; /* Upper limit on a processed batch */ 352 353 /* 3) dynticks interface. */ 354 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ 355 int dynticks_snap; /* Per-GP tracking for dynticks. */ 356 357 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ 358 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ 359 unsigned long offline_fqs; /* Kicked due to being offline. */ 360 unsigned long cond_resched_completed; 361 /* Grace period that needs help */ 362 /* from cond_resched(). */ 363 364 /* 5) __rcu_pending() statistics. */ 365 unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */ 366 unsigned long n_rp_qs_pending; 367 unsigned long n_rp_report_qs; 368 unsigned long n_rp_cb_ready; 369 unsigned long n_rp_cpu_needs_gp; 370 unsigned long n_rp_gp_completed; 371 unsigned long n_rp_gp_started; 372 unsigned long n_rp_nocb_defer_wakeup; 373 unsigned long n_rp_need_nothing; 374 375 /* 6) _rcu_barrier(), OOM callbacks, and expediting. */ 376 struct rcu_head barrier_head; 377 #ifdef CONFIG_RCU_FAST_NO_HZ 378 struct rcu_head oom_head; 379 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ 380 struct mutex exp_funnel_mutex; 381 bool exp_done; /* Expedited QS for this CPU? */ 382 383 /* 7) Callback offloading. */ 384 #ifdef CONFIG_RCU_NOCB_CPU 385 struct rcu_head *nocb_head; /* CBs waiting for kthread. */ 386 struct rcu_head **nocb_tail; 387 atomic_long_t nocb_q_count; /* # CBs waiting for nocb */ 388 atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */ 389 struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */ 390 struct rcu_head **nocb_follower_tail; 391 wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */ 392 struct task_struct *nocb_kthread; 393 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ 394 395 /* The following fields are used by the leader, hence own cacheline. */ 396 struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp; 397 /* CBs waiting for GP. */ 398 struct rcu_head **nocb_gp_tail; 399 bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */ 400 struct rcu_data *nocb_next_follower; 401 /* Next follower in wakeup chain. */ 402 403 /* The following fields are used by the follower, hence new cachline. */ 404 struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp; 405 /* Leader CPU takes GP-end wakeups. */ 406 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 407 408 /* 8) RCU CPU stall data. */ 409 unsigned int softirq_snap; /* Snapshot of softirq activity. */ 410 411 int cpu; 412 struct rcu_state *rsp; 413 }; 414 415 /* Values for fqs_state field in struct rcu_state. */ 416 #define RCU_GP_IDLE 0 /* No grace period in progress. */ 417 #define RCU_GP_INIT 1 /* Grace period being initialized. */ 418 #define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */ 419 #define RCU_FORCE_QS 3 /* Need to force quiescent state. */ 420 #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK 421 422 /* Values for nocb_defer_wakeup field in struct rcu_data. */ 423 #define RCU_NOGP_WAKE_NOT 0 424 #define RCU_NOGP_WAKE 1 425 #define RCU_NOGP_WAKE_FORCE 2 426 427 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) 428 /* For jiffies_till_first_fqs and */ 429 /* and jiffies_till_next_fqs. */ 430 431 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ 432 /* delay between bouts of */ 433 /* quiescent-state forcing. */ 434 435 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ 436 /* at least one scheduling clock */ 437 /* irq before ratting on them. */ 438 439 #define rcu_wait(cond) \ 440 do { \ 441 for (;;) { \ 442 set_current_state(TASK_INTERRUPTIBLE); \ 443 if (cond) \ 444 break; \ 445 schedule(); \ 446 } \ 447 __set_current_state(TASK_RUNNING); \ 448 } while (0) 449 450 /* 451 * RCU global state, including node hierarchy. This hierarchy is 452 * represented in "heap" form in a dense array. The root (first level) 453 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 454 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 455 * and the third level in ->node[m+1] and following (->node[m+1] referenced 456 * by ->level[2]). The number of levels is determined by the number of 457 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 458 * consisting of a single rcu_node. 459 */ 460 struct rcu_state { 461 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 462 struct rcu_node *level[RCU_NUM_LVLS + 1]; 463 /* Hierarchy levels (+1 to */ 464 /* shut bogus gcc warning) */ 465 u8 flavor_mask; /* bit in flavor mask. */ 466 struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ 467 void (*call)(struct rcu_head *head, /* call_rcu() flavor. */ 468 void (*func)(struct rcu_head *head)); 469 470 /* The following fields are guarded by the root rcu_node's lock. */ 471 472 u8 fqs_state ____cacheline_internodealigned_in_smp; 473 /* Force QS state. */ 474 u8 boost; /* Subject to priority boost. */ 475 unsigned long gpnum; /* Current gp number. */ 476 unsigned long completed; /* # of last completed gp. */ 477 struct task_struct *gp_kthread; /* Task for grace periods. */ 478 wait_queue_head_t gp_wq; /* Where GP task waits. */ 479 short gp_flags; /* Commands for GP task. */ 480 short gp_state; /* GP kthread sleep state. */ 481 482 /* End of fields guarded by root rcu_node's lock. */ 483 484 raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp; 485 /* Protect following fields. */ 486 struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */ 487 /* need a grace period. */ 488 struct rcu_head **orphan_nxttail; /* Tail of above. */ 489 struct rcu_head *orphan_donelist; /* Orphaned callbacks that */ 490 /* are ready to invoke. */ 491 struct rcu_head **orphan_donetail; /* Tail of above. */ 492 long qlen_lazy; /* Number of lazy callbacks. */ 493 long qlen; /* Total number of callbacks. */ 494 /* End of fields guarded by orphan_lock. */ 495 496 struct mutex barrier_mutex; /* Guards barrier fields. */ 497 atomic_t barrier_cpu_count; /* # CPUs waiting on. */ 498 struct completion barrier_completion; /* Wake at barrier end. */ 499 unsigned long barrier_sequence; /* ++ at start and end of */ 500 /* _rcu_barrier(). */ 501 /* End of fields guarded by barrier_mutex. */ 502 503 unsigned long expedited_sequence; /* Take a ticket. */ 504 atomic_long_t expedited_workdone0; /* # done by others #0. */ 505 atomic_long_t expedited_workdone1; /* # done by others #1. */ 506 atomic_long_t expedited_workdone2; /* # done by others #2. */ 507 atomic_long_t expedited_workdone3; /* # done by others #3. */ 508 atomic_long_t expedited_normal; /* # fallbacks to normal. */ 509 atomic_t expedited_need_qs; /* # CPUs left to check in. */ 510 wait_queue_head_t expedited_wq; /* Wait for check-ins. */ 511 512 unsigned long jiffies_force_qs; /* Time at which to invoke */ 513 /* force_quiescent_state(). */ 514 unsigned long n_force_qs; /* Number of calls to */ 515 /* force_quiescent_state(). */ 516 unsigned long n_force_qs_lh; /* ~Number of calls leaving */ 517 /* due to lock unavailable. */ 518 unsigned long n_force_qs_ngp; /* Number of calls leaving */ 519 /* due to no GP active. */ 520 unsigned long gp_start; /* Time at which GP started, */ 521 /* but in jiffies. */ 522 unsigned long gp_activity; /* Time of last GP kthread */ 523 /* activity in jiffies. */ 524 unsigned long jiffies_stall; /* Time at which to check */ 525 /* for CPU stalls. */ 526 unsigned long jiffies_resched; /* Time at which to resched */ 527 /* a reluctant CPU. */ 528 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ 529 /* GP start. */ 530 unsigned long gp_max; /* Maximum GP duration in */ 531 /* jiffies. */ 532 const char *name; /* Name of structure. */ 533 char abbr; /* Abbreviated name. */ 534 struct list_head flavors; /* List of RCU flavors. */ 535 }; 536 537 /* Values for rcu_state structure's gp_flags field. */ 538 #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ 539 #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ 540 541 /* Values for rcu_state structure's gp_flags field. */ 542 #define RCU_GP_WAIT_INIT 0 /* Initial state. */ 543 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ 544 #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ 545 #define RCU_GP_WAIT_FQS 3 /* Wait for force-quiescent-state time. */ 546 #define RCU_GP_DOING_FQS 4 /* Wait done for force-quiescent-state time. */ 547 #define RCU_GP_CLEANUP 5 /* Grace-period cleanup started. */ 548 #define RCU_GP_CLEANED 6 /* Grace-period cleanup complete. */ 549 550 extern struct list_head rcu_struct_flavors; 551 552 /* Sequence through rcu_state structures for each RCU flavor. */ 553 #define for_each_rcu_flavor(rsp) \ 554 list_for_each_entry((rsp), &rcu_struct_flavors, flavors) 555 556 /* 557 * RCU implementation internal declarations: 558 */ 559 extern struct rcu_state rcu_sched_state; 560 561 extern struct rcu_state rcu_bh_state; 562 563 #ifdef CONFIG_PREEMPT_RCU 564 extern struct rcu_state rcu_preempt_state; 565 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 566 567 #ifdef CONFIG_RCU_BOOST 568 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); 569 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu); 570 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); 571 DECLARE_PER_CPU(char, rcu_cpu_has_work); 572 #endif /* #ifdef CONFIG_RCU_BOOST */ 573 574 #ifndef RCU_TREE_NONCORE 575 576 /* Forward declarations for rcutree_plugin.h */ 577 static void rcu_bootup_announce(void); 578 static void rcu_preempt_note_context_switch(void); 579 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 580 #ifdef CONFIG_HOTPLUG_CPU 581 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 582 #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 583 static void rcu_print_detail_task_stall(struct rcu_state *rsp); 584 static int rcu_print_task_stall(struct rcu_node *rnp); 585 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); 586 static void rcu_preempt_check_callbacks(void); 587 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); 588 static void __init __rcu_init_preempt(void); 589 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 590 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 591 static void invoke_rcu_callbacks_kthread(void); 592 static bool rcu_is_callbacks_kthread(void); 593 #ifdef CONFIG_RCU_BOOST 594 static void rcu_preempt_do_callbacks(void); 595 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, 596 struct rcu_node *rnp); 597 #endif /* #ifdef CONFIG_RCU_BOOST */ 598 static void __init rcu_spawn_boost_kthreads(void); 599 static void rcu_prepare_kthreads(int cpu); 600 static void rcu_cleanup_after_idle(void); 601 static void rcu_prepare_for_idle(void); 602 static void rcu_idle_count_callbacks_posted(void); 603 static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 604 static void print_cpu_stall_info_begin(void); 605 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu); 606 static void print_cpu_stall_info_end(void); 607 static void zero_cpu_stall_ticks(struct rcu_data *rdp); 608 static void increment_cpu_stall_ticks(void); 609 static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu); 610 static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq); 611 static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp); 612 static void rcu_init_one_nocb(struct rcu_node *rnp); 613 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, 614 bool lazy, unsigned long flags); 615 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, 616 struct rcu_data *rdp, 617 unsigned long flags); 618 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); 619 static void do_nocb_deferred_wakeup(struct rcu_data *rdp); 620 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); 621 static void rcu_spawn_all_nocb_kthreads(int cpu); 622 static void __init rcu_spawn_nocb_kthreads(void); 623 #ifdef CONFIG_RCU_NOCB_CPU 624 static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp); 625 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 626 static void __maybe_unused rcu_kick_nohz_cpu(int cpu); 627 static bool init_nocb_callback_list(struct rcu_data *rdp); 628 static void rcu_sysidle_enter(int irq); 629 static void rcu_sysidle_exit(int irq); 630 static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, 631 unsigned long *maxj); 632 static bool is_sysidle_rcu_state(struct rcu_state *rsp); 633 static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, 634 unsigned long maxj); 635 static void rcu_bind_gp_kthread(void); 636 static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp); 637 static bool rcu_nohz_full_cpu(struct rcu_state *rsp); 638 static void rcu_dynticks_task_enter(void); 639 static void rcu_dynticks_task_exit(void); 640 641 #endif /* #ifndef RCU_TREE_NONCORE */ 642 643 #ifdef CONFIG_RCU_TRACE 644 /* Read out queue lengths for tracing. */ 645 static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll) 646 { 647 #ifdef CONFIG_RCU_NOCB_CPU 648 *ql = atomic_long_read(&rdp->nocb_q_count); 649 *qll = atomic_long_read(&rdp->nocb_q_count_lazy); 650 #else /* #ifdef CONFIG_RCU_NOCB_CPU */ 651 *ql = 0; 652 *qll = 0; 653 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 654 } 655 #endif /* #ifdef CONFIG_RCU_TRACE */ 656 657 /* 658 * Place this after a lock-acquisition primitive to guarantee that 659 * an UNLOCK+LOCK pair act as a full barrier. This guarantee applies 660 * if the UNLOCK and LOCK are executed by the same CPU or if the 661 * UNLOCK and LOCK operate on the same lock variable. 662 */ 663 #ifdef CONFIG_PPC 664 #define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ 665 #else /* #ifdef CONFIG_PPC */ 666 #define smp_mb__after_unlock_lock() do { } while (0) 667 #endif /* #else #ifdef CONFIG_PPC */ 668