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 /* Adjust sequence number for start of update-side operation. */ 65 static inline void rcu_seq_start(unsigned long *sp) 66 { 67 WRITE_ONCE(*sp, *sp + 1); 68 smp_mb(); /* Ensure update-side operation after counter increment. */ 69 WARN_ON_ONCE(!(*sp & 0x1)); 70 } 71 72 /* Adjust sequence number for end of update-side operation. */ 73 static inline void rcu_seq_end(unsigned long *sp) 74 { 75 smp_mb(); /* Ensure update-side operation before counter increment. */ 76 WARN_ON_ONCE(!(*sp & 0x1)); 77 WRITE_ONCE(*sp, *sp + 1); 78 } 79 80 /* Take a snapshot of the update side's sequence number. */ 81 static inline unsigned long rcu_seq_snap(unsigned long *sp) 82 { 83 unsigned long s; 84 85 s = (READ_ONCE(*sp) + 3) & ~0x1; 86 smp_mb(); /* Above access must not bleed into critical section. */ 87 return s; 88 } 89 90 /* Return the current value the update side's sequence number, no ordering. */ 91 static inline unsigned long rcu_seq_current(unsigned long *sp) 92 { 93 return READ_ONCE(*sp); 94 } 95 96 /* 97 * Given a snapshot from rcu_seq_snap(), determine whether or not a 98 * full update-side operation has occurred. 99 */ 100 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s) 101 { 102 return ULONG_CMP_GE(READ_ONCE(*sp), s); 103 } 104 105 /* 106 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally 107 * by call_rcu() and rcu callback execution, and are therefore not part of the 108 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. 109 */ 110 111 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD 112 # define STATE_RCU_HEAD_READY 0 113 # define STATE_RCU_HEAD_QUEUED 1 114 115 extern struct debug_obj_descr rcuhead_debug_descr; 116 117 static inline int debug_rcu_head_queue(struct rcu_head *head) 118 { 119 int r1; 120 121 r1 = debug_object_activate(head, &rcuhead_debug_descr); 122 debug_object_active_state(head, &rcuhead_debug_descr, 123 STATE_RCU_HEAD_READY, 124 STATE_RCU_HEAD_QUEUED); 125 return r1; 126 } 127 128 static inline void debug_rcu_head_unqueue(struct rcu_head *head) 129 { 130 debug_object_active_state(head, &rcuhead_debug_descr, 131 STATE_RCU_HEAD_QUEUED, 132 STATE_RCU_HEAD_READY); 133 debug_object_deactivate(head, &rcuhead_debug_descr); 134 } 135 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 136 static inline int debug_rcu_head_queue(struct rcu_head *head) 137 { 138 return 0; 139 } 140 141 static inline void debug_rcu_head_unqueue(struct rcu_head *head) 142 { 143 } 144 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 145 146 void kfree(const void *); 147 148 /* 149 * Reclaim the specified callback, either by invoking it (non-lazy case) 150 * or freeing it directly (lazy case). Return true if lazy, false otherwise. 151 */ 152 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head) 153 { 154 unsigned long offset = (unsigned long)head->func; 155 156 rcu_lock_acquire(&rcu_callback_map); 157 if (__is_kfree_rcu_offset(offset)) { 158 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);) 159 kfree((void *)head - offset); 160 rcu_lock_release(&rcu_callback_map); 161 return true; 162 } else { 163 RCU_TRACE(trace_rcu_invoke_callback(rn, head);) 164 head->func(head); 165 rcu_lock_release(&rcu_callback_map); 166 return false; 167 } 168 } 169 170 #ifdef CONFIG_RCU_STALL_COMMON 171 172 extern int rcu_cpu_stall_suppress; 173 int rcu_jiffies_till_stall_check(void); 174 175 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ 176 177 /* 178 * Strings used in tracepoints need to be exported via the 179 * tracing system such that tools like perf and trace-cmd can 180 * translate the string address pointers to actual text. 181 */ 182 #define TPS(x) tracepoint_string(x) 183 184 void rcu_early_boot_tests(void); 185 void rcu_test_sync_prims(void); 186 187 /* 188 * This function really isn't for public consumption, but RCU is special in 189 * that context switches can allow the state machine to make progress. 190 */ 191 extern void resched_cpu(int cpu); 192 193 #if defined(SRCU) || !defined(TINY_RCU) 194 195 #include <linux/rcu_node_tree.h> 196 197 extern int rcu_num_lvls; 198 extern int num_rcu_lvl[]; 199 extern int rcu_num_nodes; 200 static bool rcu_fanout_exact; 201 static int rcu_fanout_leaf; 202 203 /* 204 * Compute the per-level fanout, either using the exact fanout specified 205 * or balancing the tree, depending on the rcu_fanout_exact boot parameter. 206 */ 207 static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) 208 { 209 int i; 210 211 if (rcu_fanout_exact) { 212 levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; 213 for (i = rcu_num_lvls - 2; i >= 0; i--) 214 levelspread[i] = RCU_FANOUT; 215 } else { 216 int ccur; 217 int cprv; 218 219 cprv = nr_cpu_ids; 220 for (i = rcu_num_lvls - 1; i >= 0; i--) { 221 ccur = levelcnt[i]; 222 levelspread[i] = (cprv + ccur - 1) / ccur; 223 cprv = ccur; 224 } 225 } 226 } 227 228 /* 229 * Do a full breadth-first scan of the rcu_node structures for the 230 * specified rcu_state structure. 231 */ 232 #define rcu_for_each_node_breadth_first(rsp, rnp) \ 233 for ((rnp) = &(rsp)->node[0]; \ 234 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) 235 236 /* 237 * Do a breadth-first scan of the non-leaf rcu_node structures for the 238 * specified rcu_state structure. Note that if there is a singleton 239 * rcu_node tree with but one rcu_node structure, this loop is a no-op. 240 */ 241 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ 242 for ((rnp) = &(rsp)->node[0]; \ 243 (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++) 244 245 /* 246 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state 247 * structure. Note that if there is a singleton rcu_node tree with but 248 * one rcu_node structure, this loop -will- visit the rcu_node structure. 249 * It is still a leaf node, even if it is also the root node. 250 */ 251 #define rcu_for_each_leaf_node(rsp, rnp) \ 252 for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \ 253 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) 254 255 /* 256 * Iterate over all possible CPUs in a leaf RCU node. 257 */ 258 #define for_each_leaf_node_possible_cpu(rnp, cpu) \ 259 for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \ 260 cpu <= rnp->grphi; \ 261 cpu = cpumask_next((cpu), cpu_possible_mask)) 262 263 #endif /* #if defined(SRCU) || !defined(TINY_RCU) */ 264 265 #endif /* __LINUX_RCU_H */ 266