rcutree.h revision ac44021fccd8f1f2b267b004f23a2e8d7ef05f7b
1/* 2 * Read-Copy Update mechanism for mutual exclusion (tree-based version) 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, write to the Free Software 16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 17 * 18 * Copyright IBM Corporation, 2008 19 * 20 * Author: Dipankar Sarma <dipankar@in.ibm.com> 21 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical algorithm 22 * 23 * Based on the original work by Paul McKenney <paulmck@us.ibm.com> 24 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. 25 * 26 * For detailed explanation of Read-Copy Update mechanism see - 27 * Documentation/RCU 28 */ 29 30#ifndef __LINUX_RCUTREE_H 31#define __LINUX_RCUTREE_H 32 33#include <linux/cache.h> 34#include <linux/spinlock.h> 35#include <linux/threads.h> 36#include <linux/cpumask.h> 37#include <linux/seqlock.h> 38 39/* 40 * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT. 41 * In theory, it should be possible to add more levels straightforwardly. 42 * In practice, this has not been tested, so there is probably some 43 * bug somewhere. 44 */ 45#define MAX_RCU_LVLS 3 46#define RCU_FANOUT (CONFIG_RCU_FANOUT) 47#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) 48#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT) 49 50#if NR_CPUS <= RCU_FANOUT 51# define NUM_RCU_LVLS 1 52# define NUM_RCU_LVL_0 1 53# define NUM_RCU_LVL_1 (NR_CPUS) 54# define NUM_RCU_LVL_2 0 55# define NUM_RCU_LVL_3 0 56#elif NR_CPUS <= RCU_FANOUT_SQ 57# define NUM_RCU_LVLS 2 58# define NUM_RCU_LVL_0 1 59# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT) 60# define NUM_RCU_LVL_2 (NR_CPUS) 61# define NUM_RCU_LVL_3 0 62#elif NR_CPUS <= RCU_FANOUT_CUBE 63# define NUM_RCU_LVLS 3 64# define NUM_RCU_LVL_0 1 65# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ) 66# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT)) 67# define NUM_RCU_LVL_3 NR_CPUS 68#else 69# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" 70#endif /* #if (NR_CPUS) <= RCU_FANOUT */ 71 72#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) 73#define NUM_RCU_NODES (RCU_SUM - NR_CPUS) 74 75/* 76 * Dynticks per-CPU state. 77 */ 78struct rcu_dynticks { 79 int dynticks_nesting; /* Track nesting level, sort of. */ 80 int dynticks; /* Even value for dynticks-idle, else odd. */ 81 int dynticks_nmi; /* Even value for either dynticks-idle or */ 82 /* not in nmi handler, else odd. So this */ 83 /* remains even for nmi from irq handler. */ 84}; 85 86/* 87 * Definition for node within the RCU grace-period-detection hierarchy. 88 */ 89struct rcu_node { 90 spinlock_t lock; 91 unsigned long qsmask; /* CPUs or groups that need to switch in */ 92 /* order for current grace period to proceed.*/ 93 unsigned long qsmaskinit; 94 /* Per-GP initialization for qsmask. */ 95 unsigned long grpmask; /* Mask to apply to parent qsmask. */ 96 int grplo; /* lowest-numbered CPU or group here. */ 97 int grphi; /* highest-numbered CPU or group here. */ 98 u8 grpnum; /* CPU/group number for next level up. */ 99 u8 level; /* root is at level 0. */ 100 struct rcu_node *parent; 101} ____cacheline_internodealigned_in_smp; 102 103/* Index values for nxttail array in struct rcu_data. */ 104#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ 105#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ 106#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ 107#define RCU_NEXT_TAIL 3 108#define RCU_NEXT_SIZE 4 109 110/* Per-CPU data for read-copy update. */ 111struct rcu_data { 112 /* 1) quiescent-state and grace-period handling : */ 113 long completed; /* Track rsp->completed gp number */ 114 /* in order to detect GP end. */ 115 long gpnum; /* Highest gp number that this CPU */ 116 /* is aware of having started. */ 117 long passed_quiesc_completed; 118 /* Value of completed at time of qs. */ 119 bool passed_quiesc; /* User-mode/idle loop etc. */ 120 bool qs_pending; /* Core waits for quiesc state. */ 121 bool beenonline; /* CPU online at least once. */ 122 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 123 unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 124 125 /* 2) batch handling */ 126 /* 127 * If nxtlist is not NULL, it is partitioned as follows. 128 * Any of the partitions might be empty, in which case the 129 * pointer to that partition will be equal to the pointer for 130 * the following partition. When the list is empty, all of 131 * the nxttail elements point to nxtlist, which is NULL. 132 * 133 * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]): 134 * Entries that might have arrived after current GP ended 135 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): 136 * Entries known to have arrived before current GP ended 137 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): 138 * Entries that batch # <= ->completed - 1: waiting for current GP 139 * [nxtlist, *nxttail[RCU_DONE_TAIL]): 140 * Entries that batch # <= ->completed 141 * The grace period for these entries has completed, and 142 * the other grace-period-completed entries may be moved 143 * here temporarily in rcu_process_callbacks(). 144 */ 145 struct rcu_head *nxtlist; 146 struct rcu_head **nxttail[RCU_NEXT_SIZE]; 147 long qlen; /* # of queued callbacks */ 148 long blimit; /* Upper limit on a processed batch */ 149 150#ifdef CONFIG_NO_HZ 151 /* 3) dynticks interface. */ 152 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ 153 int dynticks_snap; /* Per-GP tracking for dynticks. */ 154 int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ 155#endif /* #ifdef CONFIG_NO_HZ */ 156 157 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ 158#ifdef CONFIG_NO_HZ 159 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ 160#endif /* #ifdef CONFIG_NO_HZ */ 161 unsigned long offline_fqs; /* Kicked due to being offline. */ 162 unsigned long resched_ipi; /* Sent a resched IPI. */ 163 164 /* 5) state to allow this CPU to force_quiescent_state on others */ 165 long n_rcu_pending; /* rcu_pending() calls since boot. */ 166 long n_rcu_pending_force_qs; /* when to force quiescent states. */ 167 168 int cpu; 169}; 170 171/* Values for signaled field in struct rcu_state. */ 172#define RCU_GP_INIT 0 /* Grace period being initialized. */ 173#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */ 174#define RCU_FORCE_QS 2 /* Need to force quiescent state. */ 175#ifdef CONFIG_NO_HZ 176#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK 177#else /* #ifdef CONFIG_NO_HZ */ 178#define RCU_SIGNAL_INIT RCU_FORCE_QS 179#endif /* #else #ifdef CONFIG_NO_HZ */ 180 181#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ 182#ifdef CONFIG_RCU_CPU_STALL_DETECTOR 183#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ 184#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */ 185#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ 186 /* to take at least one */ 187 /* scheduling clock irq */ 188 /* before ratting on them. */ 189 190#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ 191 192/* 193 * RCU global state, including node hierarchy. This hierarchy is 194 * represented in "heap" form in a dense array. The root (first level) 195 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 196 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 197 * and the third level in ->node[m+1] and following (->node[m+1] referenced 198 * by ->level[2]). The number of levels is determined by the number of 199 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 200 * consisting of a single rcu_node. 201 */ 202struct rcu_state { 203 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 204 struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ 205 u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ 206 u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ 207 struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */ 208 209 /* The following fields are guarded by the root rcu_node's lock. */ 210 211 u8 signaled ____cacheline_internodealigned_in_smp; 212 /* Force QS state. */ 213 long gpnum; /* Current gp number. */ 214 long completed; /* # of last completed gp. */ 215 spinlock_t onofflock; /* exclude on/offline and */ 216 /* starting new GP. */ 217 spinlock_t fqslock; /* Only one task forcing */ 218 /* quiescent states. */ 219 unsigned long jiffies_force_qs; /* Time at which to invoke */ 220 /* force_quiescent_state(). */ 221 unsigned long n_force_qs; /* Number of calls to */ 222 /* force_quiescent_state(). */ 223 unsigned long n_force_qs_lh; /* ~Number of calls leaving */ 224 /* due to lock unavailable. */ 225 unsigned long n_force_qs_ngp; /* Number of calls leaving */ 226 /* due to no GP active. */ 227#ifdef CONFIG_RCU_CPU_STALL_DETECTOR 228 unsigned long gp_start; /* Time at which GP started, */ 229 /* but in jiffies. */ 230 unsigned long jiffies_stall; /* Time at which to check */ 231 /* for CPU stalls. */ 232#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ 233#ifdef CONFIG_NO_HZ 234 long dynticks_completed; /* Value of completed @ snap. */ 235#endif /* #ifdef CONFIG_NO_HZ */ 236}; 237 238extern void rcu_qsctr_inc(int cpu); 239extern void rcu_bh_qsctr_inc(int cpu); 240 241extern int rcu_pending(int cpu); 242extern int rcu_needs_cpu(int cpu); 243 244#ifdef CONFIG_DEBUG_LOCK_ALLOC 245extern struct lockdep_map rcu_lock_map; 246# define rcu_read_acquire() \ 247 lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) 248# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) 249#else 250# define rcu_read_acquire() do { } while (0) 251# define rcu_read_release() do { } while (0) 252#endif 253 254static inline void __rcu_read_lock(void) 255{ 256 preempt_disable(); 257 __acquire(RCU); 258 rcu_read_acquire(); 259} 260static inline void __rcu_read_unlock(void) 261{ 262 rcu_read_release(); 263 __release(RCU); 264 preempt_enable(); 265} 266static inline void __rcu_read_lock_bh(void) 267{ 268 local_bh_disable(); 269 __acquire(RCU_BH); 270 rcu_read_acquire(); 271} 272static inline void __rcu_read_unlock_bh(void) 273{ 274 rcu_read_release(); 275 __release(RCU_BH); 276 local_bh_enable(); 277} 278 279#define __synchronize_sched() synchronize_rcu() 280 281#define call_rcu_sched(head, func) call_rcu(head, func) 282 283static inline void rcu_init_sched(void) 284{ 285} 286 287extern void __rcu_init(void); 288extern void rcu_check_callbacks(int cpu, int user); 289extern void rcu_restart_cpu(int cpu); 290 291extern long rcu_batches_completed(void); 292extern long rcu_batches_completed_bh(void); 293 294#ifdef CONFIG_NO_HZ 295void rcu_enter_nohz(void); 296void rcu_exit_nohz(void); 297#else /* CONFIG_NO_HZ */ 298static inline void rcu_enter_nohz(void) 299{ 300} 301static inline void rcu_exit_nohz(void) 302{ 303} 304#endif /* CONFIG_NO_HZ */ 305 306/* A context switch is a grace period for rcutree. */ 307static inline int rcu_blocking_is_gp(void) 308{ 309 return num_online_cpus() == 1; 310} 311 312#endif /* __LINUX_RCUTREE_H */ 313