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 /* 34 * Process-level increment to ->dynticks_nesting field. This allows for 35 * architectures that use half-interrupts and half-exceptions from 36 * process context. 37 * 38 * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH 39 * that counts the number of process-based reasons why RCU cannot 40 * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE 41 * is the value used to increment or decrement this field. 42 * 43 * The rest of the bits could in principle be used to count interrupts, 44 * but this would mean that a negative-one value in the interrupt 45 * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field. 46 * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK 47 * that is set to DYNTICK_TASK_FLAG upon initial exit from idle. 48 * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon 49 * initial exit from idle. 50 */ 51 #define DYNTICK_TASK_NEST_WIDTH 7 52 #define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1) 53 #define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1) 54 #define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2) 55 #define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3) 56 #define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \ 57 DYNTICK_TASK_FLAG) 58 59 60 /* 61 * Grace-period counter management. 62 */ 63 64 #define RCU_SEQ_CTR_SHIFT 2 65 #define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1) 66 67 /* 68 * Return the counter portion of a sequence number previously returned 69 * by rcu_seq_snap() or rcu_seq_current(). 70 */ 71 static inline unsigned long rcu_seq_ctr(unsigned long s) 72 { 73 return s >> RCU_SEQ_CTR_SHIFT; 74 } 75 76 /* 77 * Return the state portion of a sequence number previously returned 78 * by rcu_seq_snap() or rcu_seq_current(). 79 */ 80 static inline int rcu_seq_state(unsigned long s) 81 { 82 return s & RCU_SEQ_STATE_MASK; 83 } 84 85 /* 86 * Set the state portion of the pointed-to sequence number. 87 * The caller is responsible for preventing conflicting updates. 88 */ 89 static inline void rcu_seq_set_state(unsigned long *sp, int newstate) 90 { 91 WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK); 92 WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate); 93 } 94 95 /* Adjust sequence number for start of update-side operation. */ 96 static inline void rcu_seq_start(unsigned long *sp) 97 { 98 WRITE_ONCE(*sp, *sp + 1); 99 smp_mb(); /* Ensure update-side operation after counter increment. */ 100 WARN_ON_ONCE(rcu_seq_state(*sp) != 1); 101 } 102 103 /* Adjust sequence number for end of update-side operation. */ 104 static inline void rcu_seq_end(unsigned long *sp) 105 { 106 smp_mb(); /* Ensure update-side operation before counter increment. */ 107 WARN_ON_ONCE(!rcu_seq_state(*sp)); 108 WRITE_ONCE(*sp, (*sp | RCU_SEQ_STATE_MASK) + 1); 109 } 110 111 /* Take a snapshot of the update side's sequence number. */ 112 static inline unsigned long rcu_seq_snap(unsigned long *sp) 113 { 114 unsigned long s; 115 116 s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK; 117 smp_mb(); /* Above access must not bleed into critical section. */ 118 return s; 119 } 120 121 /* Return the current value the update side's sequence number, no ordering. */ 122 static inline unsigned long rcu_seq_current(unsigned long *sp) 123 { 124 return READ_ONCE(*sp); 125 } 126 127 /* 128 * Given a snapshot from rcu_seq_snap(), determine whether or not a 129 * full update-side operation has occurred. 130 */ 131 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s) 132 { 133 return ULONG_CMP_GE(READ_ONCE(*sp), s); 134 } 135 136 /* 137 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally 138 * by call_rcu() and rcu callback execution, and are therefore not part of the 139 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. 140 */ 141 142 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD 143 # define STATE_RCU_HEAD_READY 0 144 # define STATE_RCU_HEAD_QUEUED 1 145 146 extern struct debug_obj_descr rcuhead_debug_descr; 147 148 static inline int debug_rcu_head_queue(struct rcu_head *head) 149 { 150 int r1; 151 152 r1 = debug_object_activate(head, &rcuhead_debug_descr); 153 debug_object_active_state(head, &rcuhead_debug_descr, 154 STATE_RCU_HEAD_READY, 155 STATE_RCU_HEAD_QUEUED); 156 return r1; 157 } 158 159 static inline void debug_rcu_head_unqueue(struct rcu_head *head) 160 { 161 debug_object_active_state(head, &rcuhead_debug_descr, 162 STATE_RCU_HEAD_QUEUED, 163 STATE_RCU_HEAD_READY); 164 debug_object_deactivate(head, &rcuhead_debug_descr); 165 } 166 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 167 static inline int debug_rcu_head_queue(struct rcu_head *head) 168 { 169 return 0; 170 } 171 172 static inline void debug_rcu_head_unqueue(struct rcu_head *head) 173 { 174 } 175 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 176 177 void kfree(const void *); 178 179 /* 180 * Reclaim the specified callback, either by invoking it (non-lazy case) 181 * or freeing it directly (lazy case). Return true if lazy, false otherwise. 182 */ 183 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head) 184 { 185 unsigned long offset = (unsigned long)head->func; 186 187 rcu_lock_acquire(&rcu_callback_map); 188 if (__is_kfree_rcu_offset(offset)) { 189 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);) 190 kfree((void *)head - offset); 191 rcu_lock_release(&rcu_callback_map); 192 return true; 193 } else { 194 RCU_TRACE(trace_rcu_invoke_callback(rn, head);) 195 head->func(head); 196 rcu_lock_release(&rcu_callback_map); 197 return false; 198 } 199 } 200 201 #ifdef CONFIG_RCU_STALL_COMMON 202 203 extern int rcu_cpu_stall_suppress; 204 int rcu_jiffies_till_stall_check(void); 205 206 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ 207 208 /* 209 * Strings used in tracepoints need to be exported via the 210 * tracing system such that tools like perf and trace-cmd can 211 * translate the string address pointers to actual text. 212 */ 213 #define TPS(x) tracepoint_string(x) 214 215 void rcu_early_boot_tests(void); 216 void rcu_test_sync_prims(void); 217 218 /* 219 * This function really isn't for public consumption, but RCU is special in 220 * that context switches can allow the state machine to make progress. 221 */ 222 extern void resched_cpu(int cpu); 223 224 #if defined(SRCU) || !defined(TINY_RCU) 225 226 #include <linux/rcu_node_tree.h> 227 228 extern int rcu_num_lvls; 229 extern int num_rcu_lvl[]; 230 extern int rcu_num_nodes; 231 static bool rcu_fanout_exact; 232 static int rcu_fanout_leaf; 233 234 /* 235 * Compute the per-level fanout, either using the exact fanout specified 236 * or balancing the tree, depending on the rcu_fanout_exact boot parameter. 237 */ 238 static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) 239 { 240 int i; 241 242 if (rcu_fanout_exact) { 243 levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; 244 for (i = rcu_num_lvls - 2; i >= 0; i--) 245 levelspread[i] = RCU_FANOUT; 246 } else { 247 int ccur; 248 int cprv; 249 250 cprv = nr_cpu_ids; 251 for (i = rcu_num_lvls - 1; i >= 0; i--) { 252 ccur = levelcnt[i]; 253 levelspread[i] = (cprv + ccur - 1) / ccur; 254 cprv = ccur; 255 } 256 } 257 } 258 259 /* 260 * Do a full breadth-first scan of the rcu_node structures for the 261 * specified rcu_state structure. 262 */ 263 #define rcu_for_each_node_breadth_first(rsp, rnp) \ 264 for ((rnp) = &(rsp)->node[0]; \ 265 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) 266 267 /* 268 * Do a breadth-first scan of the non-leaf rcu_node structures for the 269 * specified rcu_state structure. Note that if there is a singleton 270 * rcu_node tree with but one rcu_node structure, this loop is a no-op. 271 */ 272 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ 273 for ((rnp) = &(rsp)->node[0]; \ 274 (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++) 275 276 /* 277 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state 278 * structure. Note that if there is a singleton rcu_node tree with but 279 * one rcu_node structure, this loop -will- visit the rcu_node structure. 280 * It is still a leaf node, even if it is also the root node. 281 */ 282 #define rcu_for_each_leaf_node(rsp, rnp) \ 283 for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \ 284 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) 285 286 /* 287 * Iterate over all possible CPUs in a leaf RCU node. 288 */ 289 #define for_each_leaf_node_possible_cpu(rnp, cpu) \ 290 for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \ 291 cpu <= rnp->grphi; \ 292 cpu = cpumask_next((cpu), cpu_possible_mask)) 293 294 #endif /* #if defined(SRCU) || !defined(TINY_RCU) */ 295 296 #endif /* __LINUX_RCU_H */ 297