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 <[email protected]> 21 * Paul E. McKenney <[email protected]> Hierarchical algorithm 22 * 23 * Based on the original work by Paul McKenney <[email protected]> 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 */ 78 struct 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 */ 89 struct 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. */ 111 struct 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) For future __rcu_pending statistics. */ 165 long n_rcu_pending; /* rcu_pending() calls since boot. */ 166 167 int cpu; 168 }; 169 170 /* Values for signaled field in struct rcu_state. */ 171 #define RCU_GP_INIT 0 /* Grace period being initialized. */ 172 #define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */ 173 #define RCU_FORCE_QS 2 /* Need to force quiescent state. */ 174 #ifdef CONFIG_NO_HZ 175 #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK 176 #else /* #ifdef CONFIG_NO_HZ */ 177 #define RCU_SIGNAL_INIT RCU_FORCE_QS 178 #endif /* #else #ifdef CONFIG_NO_HZ */ 179 180 #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ 181 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR 182 #define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ 183 #define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */ 184 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ 185 /* to take at least one */ 186 /* scheduling clock irq */ 187 /* before ratting on them. */ 188 189 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ 190 191 /* 192 * RCU global state, including node hierarchy. This hierarchy is 193 * represented in "heap" form in a dense array. The root (first level) 194 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 195 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 196 * and the third level in ->node[m+1] and following (->node[m+1] referenced 197 * by ->level[2]). The number of levels is determined by the number of 198 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 199 * consisting of a single rcu_node. 200 */ 201 struct rcu_state { 202 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 203 struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ 204 u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ 205 u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ 206 struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */ 207 208 /* The following fields are guarded by the root rcu_node's lock. */ 209 210 u8 signaled ____cacheline_internodealigned_in_smp; 211 /* Force QS state. */ 212 long gpnum; /* Current gp number. */ 213 long completed; /* # of last completed gp. */ 214 spinlock_t onofflock; /* exclude on/offline and */ 215 /* starting new GP. */ 216 spinlock_t fqslock; /* Only one task forcing */ 217 /* quiescent states. */ 218 unsigned long jiffies_force_qs; /* Time at which to invoke */ 219 /* force_quiescent_state(). */ 220 unsigned long n_force_qs; /* Number of calls to */ 221 /* force_quiescent_state(). */ 222 unsigned long n_force_qs_lh; /* ~Number of calls leaving */ 223 /* due to lock unavailable. */ 224 unsigned long n_force_qs_ngp; /* Number of calls leaving */ 225 /* due to no GP active. */ 226 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR 227 unsigned long gp_start; /* Time at which GP started, */ 228 /* but in jiffies. */ 229 unsigned long jiffies_stall; /* Time at which to check */ 230 /* for CPU stalls. */ 231 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ 232 #ifdef CONFIG_NO_HZ 233 long dynticks_completed; /* Value of completed @ snap. */ 234 #endif /* #ifdef CONFIG_NO_HZ */ 235 }; 236 237 extern void rcu_qsctr_inc(int cpu); 238 extern void rcu_bh_qsctr_inc(int cpu); 239 240 extern int rcu_pending(int cpu); 241 extern int rcu_needs_cpu(int cpu); 242 243 #ifdef CONFIG_DEBUG_LOCK_ALLOC 244 extern struct lockdep_map rcu_lock_map; 245 # define rcu_read_acquire() \ 246 lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) 247 # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) 248 #else 249 # define rcu_read_acquire() do { } while (0) 250 # define rcu_read_release() do { } while (0) 251 #endif 252 253 static inline void __rcu_read_lock(void) 254 { 255 preempt_disable(); 256 __acquire(RCU); 257 rcu_read_acquire(); 258 } 259 static inline void __rcu_read_unlock(void) 260 { 261 rcu_read_release(); 262 __release(RCU); 263 preempt_enable(); 264 } 265 static inline void __rcu_read_lock_bh(void) 266 { 267 local_bh_disable(); 268 __acquire(RCU_BH); 269 rcu_read_acquire(); 270 } 271 static inline void __rcu_read_unlock_bh(void) 272 { 273 rcu_read_release(); 274 __release(RCU_BH); 275 local_bh_enable(); 276 } 277 278 #define __synchronize_sched() synchronize_rcu() 279 280 #define call_rcu_sched(head, func) call_rcu(head, func) 281 282 static inline void rcu_init_sched(void) 283 { 284 } 285 286 extern void __rcu_init(void); 287 extern void rcu_check_callbacks(int cpu, int user); 288 extern void rcu_restart_cpu(int cpu); 289 290 extern long rcu_batches_completed(void); 291 extern long rcu_batches_completed_bh(void); 292 293 #ifdef CONFIG_NO_HZ 294 void rcu_enter_nohz(void); 295 void rcu_exit_nohz(void); 296 #else /* CONFIG_NO_HZ */ 297 static inline void rcu_enter_nohz(void) 298 { 299 } 300 static inline void rcu_exit_nohz(void) 301 { 302 } 303 #endif /* CONFIG_NO_HZ */ 304 305 /* A context switch is a grace period for rcutree. */ 306 static inline int rcu_blocking_is_gp(void) 307 { 308 return num_online_cpus() == 1; 309 } 310 311 #endif /* __LINUX_RCUTREE_H */ 312