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, write to the Free Software 17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 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 31/* 32 * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT. 33 * In theory, it should be possible to add more levels straightforwardly. 34 * In practice, this did work well going from three levels to four. 35 * Of course, your mileage may vary. 36 */ 37#define MAX_RCU_LVLS 4 38#if CONFIG_RCU_FANOUT > 16 39#define RCU_FANOUT_LEAF 16 40#else /* #if CONFIG_RCU_FANOUT > 16 */ 41#define RCU_FANOUT_LEAF (CONFIG_RCU_FANOUT) 42#endif /* #else #if CONFIG_RCU_FANOUT > 16 */ 43#define RCU_FANOUT_1 (RCU_FANOUT_LEAF) 44#define RCU_FANOUT_2 (RCU_FANOUT_1 * CONFIG_RCU_FANOUT) 45#define RCU_FANOUT_3 (RCU_FANOUT_2 * CONFIG_RCU_FANOUT) 46#define RCU_FANOUT_4 (RCU_FANOUT_3 * CONFIG_RCU_FANOUT) 47 48#if NR_CPUS <= RCU_FANOUT_1 49# define NUM_RCU_LVLS 1 50# define NUM_RCU_LVL_0 1 51# define NUM_RCU_LVL_1 (NR_CPUS) 52# define NUM_RCU_LVL_2 0 53# define NUM_RCU_LVL_3 0 54# define NUM_RCU_LVL_4 0 55#elif NR_CPUS <= RCU_FANOUT_2 56# define NUM_RCU_LVLS 2 57# define NUM_RCU_LVL_0 1 58# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 59# define NUM_RCU_LVL_2 (NR_CPUS) 60# define NUM_RCU_LVL_3 0 61# define NUM_RCU_LVL_4 0 62#elif NR_CPUS <= RCU_FANOUT_3 63# define NUM_RCU_LVLS 3 64# define NUM_RCU_LVL_0 1 65# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) 66# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 67# define NUM_RCU_LVL_3 (NR_CPUS) 68# define NUM_RCU_LVL_4 0 69#elif NR_CPUS <= RCU_FANOUT_4 70# define NUM_RCU_LVLS 4 71# define NUM_RCU_LVL_0 1 72# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) 73# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) 74# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) 75# define NUM_RCU_LVL_4 (NR_CPUS) 76#else 77# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" 78#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ 79 80#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4) 81#define NUM_RCU_NODES (RCU_SUM - NR_CPUS) 82 83/* 84 * Dynticks per-CPU state. 85 */ 86struct rcu_dynticks { 87 int dynticks_nesting; /* Track irq/process nesting level. */ 88 int dynticks_nmi_nesting; /* Track NMI nesting level. */ 89 atomic_t dynticks; /* Even value for dynticks-idle, else odd. */ 90}; 91 92/* RCU's kthread states for tracing. */ 93#define RCU_KTHREAD_STOPPED 0 94#define RCU_KTHREAD_RUNNING 1 95#define RCU_KTHREAD_WAITING 2 96#define RCU_KTHREAD_OFFCPU 3 97#define RCU_KTHREAD_YIELDING 4 98#define RCU_KTHREAD_MAX 4 99 100/* 101 * Definition for node within the RCU grace-period-detection hierarchy. 102 */ 103struct rcu_node { 104 raw_spinlock_t lock; /* Root rcu_node's lock protects some */ 105 /* rcu_state fields as well as following. */ 106 unsigned long gpnum; /* Current grace period for this node. */ 107 /* This will either be equal to or one */ 108 /* behind the root rcu_node's gpnum. */ 109 unsigned long completed; /* Last GP completed for this node. */ 110 /* This will either be equal to or one */ 111 /* behind the root rcu_node's gpnum. */ 112 unsigned long qsmask; /* CPUs or groups that need to switch in */ 113 /* order for current grace period to proceed.*/ 114 /* In leaf rcu_node, each bit corresponds to */ 115 /* an rcu_data structure, otherwise, each */ 116 /* bit corresponds to a child rcu_node */ 117 /* structure. */ 118 unsigned long expmask; /* Groups that have ->blkd_tasks */ 119 /* elements that need to drain to allow the */ 120 /* current expedited grace period to */ 121 /* complete (only for TREE_PREEMPT_RCU). */ 122 atomic_t wakemask; /* CPUs whose kthread needs to be awakened. */ 123 /* Since this has meaning only for leaf */ 124 /* rcu_node structures, 32 bits suffices. */ 125 unsigned long qsmaskinit; 126 /* Per-GP initial value for qsmask & expmask. */ 127 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 128 /* Only one bit will be set in this mask. */ 129 int grplo; /* lowest-numbered CPU or group here. */ 130 int grphi; /* highest-numbered CPU or group here. */ 131 u8 grpnum; /* CPU/group number for next level up. */ 132 u8 level; /* root is at level 0. */ 133 struct rcu_node *parent; 134 struct list_head blkd_tasks; 135 /* Tasks blocked in RCU read-side critical */ 136 /* section. Tasks are placed at the head */ 137 /* of this list and age towards the tail. */ 138 struct list_head *gp_tasks; 139 /* Pointer to the first task blocking the */ 140 /* current grace period, or NULL if there */ 141 /* is no such task. */ 142 struct list_head *exp_tasks; 143 /* Pointer to the first task blocking the */ 144 /* current expedited grace period, or NULL */ 145 /* if there is no such task. If there */ 146 /* is no current expedited grace period, */ 147 /* then there can cannot be any such task. */ 148#ifdef CONFIG_RCU_BOOST 149 struct list_head *boost_tasks; 150 /* Pointer to first task that needs to be */ 151 /* priority boosted, or NULL if no priority */ 152 /* boosting is needed for this rcu_node */ 153 /* structure. If there are no tasks */ 154 /* queued on this rcu_node structure that */ 155 /* are blocking the current grace period, */ 156 /* there can be no such task. */ 157 unsigned long boost_time; 158 /* When to start boosting (jiffies). */ 159 struct task_struct *boost_kthread_task; 160 /* kthread that takes care of priority */ 161 /* boosting for this rcu_node structure. */ 162 unsigned int boost_kthread_status; 163 /* State of boost_kthread_task for tracing. */ 164 unsigned long n_tasks_boosted; 165 /* Total number of tasks boosted. */ 166 unsigned long n_exp_boosts; 167 /* Number of tasks boosted for expedited GP. */ 168 unsigned long n_normal_boosts; 169 /* Number of tasks boosted for normal GP. */ 170 unsigned long n_balk_blkd_tasks; 171 /* Refused to boost: no blocked tasks. */ 172 unsigned long n_balk_exp_gp_tasks; 173 /* Refused to boost: nothing blocking GP. */ 174 unsigned long n_balk_boost_tasks; 175 /* Refused to boost: already boosting. */ 176 unsigned long n_balk_notblocked; 177 /* Refused to boost: RCU RS CS still running. */ 178 unsigned long n_balk_notyet; 179 /* Refused to boost: not yet time. */ 180 unsigned long n_balk_nos; 181 /* Refused to boost: not sure why, though. */ 182 /* This can happen due to race conditions. */ 183#endif /* #ifdef CONFIG_RCU_BOOST */ 184 struct task_struct *node_kthread_task; 185 /* kthread that takes care of this rcu_node */ 186 /* structure, for example, awakening the */ 187 /* per-CPU kthreads as needed. */ 188 unsigned int node_kthread_status; 189 /* State of node_kthread_task for tracing. */ 190} ____cacheline_internodealigned_in_smp; 191 192/* 193 * Do a full breadth-first scan of the rcu_node structures for the 194 * specified rcu_state structure. 195 */ 196#define rcu_for_each_node_breadth_first(rsp, rnp) \ 197 for ((rnp) = &(rsp)->node[0]; \ 198 (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) 199 200/* 201 * Do a breadth-first scan of the non-leaf rcu_node structures for the 202 * specified rcu_state structure. Note that if there is a singleton 203 * rcu_node tree with but one rcu_node structure, this loop is a no-op. 204 */ 205#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ 206 for ((rnp) = &(rsp)->node[0]; \ 207 (rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++) 208 209/* 210 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state 211 * structure. Note that if there is a singleton rcu_node tree with but 212 * one rcu_node structure, this loop -will- visit the rcu_node structure. 213 * It is still a leaf node, even if it is also the root node. 214 */ 215#define rcu_for_each_leaf_node(rsp, rnp) \ 216 for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \ 217 (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) 218 219/* Index values for nxttail array in struct rcu_data. */ 220#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ 221#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ 222#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ 223#define RCU_NEXT_TAIL 3 224#define RCU_NEXT_SIZE 4 225 226/* Per-CPU data for read-copy update. */ 227struct rcu_data { 228 /* 1) quiescent-state and grace-period handling : */ 229 unsigned long completed; /* Track rsp->completed gp number */ 230 /* in order to detect GP end. */ 231 unsigned long gpnum; /* Highest gp number that this CPU */ 232 /* is aware of having started. */ 233 unsigned long passed_quiesc_completed; 234 /* Value of completed at time of qs. */ 235 bool passed_quiesc; /* User-mode/idle loop etc. */ 236 bool qs_pending; /* Core waits for quiesc state. */ 237 bool beenonline; /* CPU online at least once. */ 238 bool preemptible; /* Preemptible RCU? */ 239 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 240 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 241 242 /* 2) batch handling */ 243 /* 244 * If nxtlist is not NULL, it is partitioned as follows. 245 * Any of the partitions might be empty, in which case the 246 * pointer to that partition will be equal to the pointer for 247 * the following partition. When the list is empty, all of 248 * the nxttail elements point to the ->nxtlist pointer itself, 249 * which in that case is NULL. 250 * 251 * [nxtlist, *nxttail[RCU_DONE_TAIL]): 252 * Entries that batch # <= ->completed 253 * The grace period for these entries has completed, and 254 * the other grace-period-completed entries may be moved 255 * here temporarily in rcu_process_callbacks(). 256 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): 257 * Entries that batch # <= ->completed - 1: waiting for current GP 258 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): 259 * Entries known to have arrived before current GP ended 260 * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]): 261 * Entries that might have arrived after current GP ended 262 * Note that the value of *nxttail[RCU_NEXT_TAIL] will 263 * always be NULL, as this is the end of the list. 264 */ 265 struct rcu_head *nxtlist; 266 struct rcu_head **nxttail[RCU_NEXT_SIZE]; 267 long qlen; /* # of queued callbacks */ 268 long qlen_last_fqs_check; 269 /* qlen at last check for QS forcing */ 270 unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */ 271 unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */ 272 unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */ 273 unsigned long n_force_qs_snap; 274 /* did other CPU force QS recently? */ 275 long blimit; /* Upper limit on a processed batch */ 276 277#ifdef CONFIG_NO_HZ 278 /* 3) dynticks interface. */ 279 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ 280 int dynticks_snap; /* Per-GP tracking for dynticks. */ 281#endif /* #ifdef CONFIG_NO_HZ */ 282 283 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ 284#ifdef CONFIG_NO_HZ 285 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ 286#endif /* #ifdef CONFIG_NO_HZ */ 287 unsigned long offline_fqs; /* Kicked due to being offline. */ 288 unsigned long resched_ipi; /* Sent a resched IPI. */ 289 290 /* 5) __rcu_pending() statistics. */ 291 unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */ 292 unsigned long n_rp_qs_pending; 293 unsigned long n_rp_report_qs; 294 unsigned long n_rp_cb_ready; 295 unsigned long n_rp_cpu_needs_gp; 296 unsigned long n_rp_gp_completed; 297 unsigned long n_rp_gp_started; 298 unsigned long n_rp_need_fqs; 299 unsigned long n_rp_need_nothing; 300 301 int cpu; 302}; 303 304/* Values for signaled field in struct rcu_state. */ 305#define RCU_GP_IDLE 0 /* No grace period in progress. */ 306#define RCU_GP_INIT 1 /* Grace period being initialized. */ 307#define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */ 308#define RCU_FORCE_QS 3 /* Need to force quiescent state. */ 309#ifdef CONFIG_NO_HZ 310#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK 311#else /* #ifdef CONFIG_NO_HZ */ 312#define RCU_SIGNAL_INIT RCU_FORCE_QS 313#endif /* #else #ifdef CONFIG_NO_HZ */ 314 315#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ 316 317#ifdef CONFIG_PROVE_RCU 318#define RCU_STALL_DELAY_DELTA (5 * HZ) 319#else 320#define RCU_STALL_DELAY_DELTA 0 321#endif 322 323#define RCU_SECONDS_TILL_STALL_CHECK (CONFIG_RCU_CPU_STALL_TIMEOUT * HZ + \ 324 RCU_STALL_DELAY_DELTA) 325 /* for rsp->jiffies_stall */ 326#define RCU_SECONDS_TILL_STALL_RECHECK (3 * RCU_SECONDS_TILL_STALL_CHECK + 30) 327 /* for rsp->jiffies_stall */ 328#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ 329 /* to take at least one */ 330 /* scheduling clock irq */ 331 /* before ratting on them. */ 332 333#define rcu_wait(cond) \ 334do { \ 335 for (;;) { \ 336 set_current_state(TASK_INTERRUPTIBLE); \ 337 if (cond) \ 338 break; \ 339 schedule(); \ 340 } \ 341 __set_current_state(TASK_RUNNING); \ 342} while (0) 343 344/* 345 * RCU global state, including node hierarchy. This hierarchy is 346 * represented in "heap" form in a dense array. The root (first level) 347 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 348 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 349 * and the third level in ->node[m+1] and following (->node[m+1] referenced 350 * by ->level[2]). The number of levels is determined by the number of 351 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 352 * consisting of a single rcu_node. 353 */ 354struct rcu_state { 355 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 356 struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ 357 u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ 358 u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ 359 struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ 360 361 /* The following fields are guarded by the root rcu_node's lock. */ 362 363 u8 signaled ____cacheline_internodealigned_in_smp; 364 /* Force QS state. */ 365 u8 fqs_active; /* force_quiescent_state() */ 366 /* is running. */ 367 u8 fqs_need_gp; /* A CPU was prevented from */ 368 /* starting a new grace */ 369 /* period because */ 370 /* force_quiescent_state() */ 371 /* was running. */ 372 u8 boost; /* Subject to priority boost. */ 373 unsigned long gpnum; /* Current gp number. */ 374 unsigned long completed; /* # of last completed gp. */ 375 376 /* End of fields guarded by root rcu_node's lock. */ 377 378 raw_spinlock_t onofflock; /* exclude on/offline and */ 379 /* starting new GP. */ 380 raw_spinlock_t fqslock; /* Only one task forcing */ 381 /* quiescent states. */ 382 unsigned long jiffies_force_qs; /* Time at which to invoke */ 383 /* force_quiescent_state(). */ 384 unsigned long n_force_qs; /* Number of calls to */ 385 /* force_quiescent_state(). */ 386 unsigned long n_force_qs_lh; /* ~Number of calls leaving */ 387 /* due to lock unavailable. */ 388 unsigned long n_force_qs_ngp; /* Number of calls leaving */ 389 /* due to no GP active. */ 390 unsigned long gp_start; /* Time at which GP started, */ 391 /* but in jiffies. */ 392 unsigned long jiffies_stall; /* Time at which to check */ 393 /* for CPU stalls. */ 394 unsigned long gp_max; /* Maximum GP duration in */ 395 /* jiffies. */ 396 char *name; /* Name of structure. */ 397}; 398 399/* Return values for rcu_preempt_offline_tasks(). */ 400 401#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */ 402 /* GP were moved to root. */ 403#define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */ 404 /* GP were moved to root. */ 405 406/* 407 * RCU implementation internal declarations: 408 */ 409extern struct rcu_state rcu_sched_state; 410DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); 411 412extern struct rcu_state rcu_bh_state; 413DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); 414 415#ifdef CONFIG_TREE_PREEMPT_RCU 416extern struct rcu_state rcu_preempt_state; 417DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); 418#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ 419 420#ifndef RCU_TREE_NONCORE 421 422/* Forward declarations for rcutree_plugin.h */ 423static void rcu_bootup_announce(void); 424long rcu_batches_completed(void); 425static void rcu_preempt_note_context_switch(int cpu); 426static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 427#ifdef CONFIG_HOTPLUG_CPU 428static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, 429 unsigned long flags); 430static void rcu_stop_cpu_kthread(int cpu); 431#endif /* #ifdef CONFIG_HOTPLUG_CPU */ 432static void rcu_print_detail_task_stall(struct rcu_state *rsp); 433static void rcu_print_task_stall(struct rcu_node *rnp); 434static void rcu_preempt_stall_reset(void); 435static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); 436#ifdef CONFIG_HOTPLUG_CPU 437static int rcu_preempt_offline_tasks(struct rcu_state *rsp, 438 struct rcu_node *rnp, 439 struct rcu_data *rdp); 440static void rcu_preempt_offline_cpu(int cpu); 441#endif /* #ifdef CONFIG_HOTPLUG_CPU */ 442static void rcu_preempt_check_callbacks(int cpu); 443static void rcu_preempt_process_callbacks(void); 444void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); 445#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) 446static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp); 447#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */ 448static int rcu_preempt_pending(int cpu); 449static int rcu_preempt_needs_cpu(int cpu); 450static void __cpuinit rcu_preempt_init_percpu_data(int cpu); 451static void rcu_preempt_send_cbs_to_online(void); 452static void __init __rcu_init_preempt(void); 453static void rcu_needs_cpu_flush(void); 454static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 455static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 456static void invoke_rcu_callbacks_kthread(void); 457#ifdef CONFIG_RCU_BOOST 458static void rcu_preempt_do_callbacks(void); 459static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, 460 cpumask_var_t cm); 461static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, 462 struct rcu_node *rnp, 463 int rnp_index); 464static void invoke_rcu_node_kthread(struct rcu_node *rnp); 465static void rcu_yield(void (*f)(unsigned long), unsigned long arg); 466#endif /* #ifdef CONFIG_RCU_BOOST */ 467static void rcu_cpu_kthread_setrt(int cpu, int to_rt); 468static void __cpuinit rcu_prepare_kthreads(int cpu); 469 470#endif /* #ifndef RCU_TREE_NONCORE */ 471