2 * Read-Copy Update definitions shared among RCU implementations.
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.
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.
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.
18 * Copyright IBM Corporation, 2011
20 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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 */
34 * Process-level increment to ->dynticks_nesting field. This allows for
35 * architectures that use half-interrupts and half-exceptions from
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.
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.
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 + \
61 * Grace-period counter management.
64 /* Adjust sequence number for start of update-side operation. */
65 static inline void rcu_seq_start(unsigned long *sp)
67 WRITE_ONCE(*sp, *sp + 1);
68 smp_mb(); /* Ensure update-side operation after counter increment. */
69 WARN_ON_ONCE(!(*sp & 0x1));
72 /* Adjust sequence number for end of update-side operation. */
73 static inline void rcu_seq_end(unsigned long *sp)
75 smp_mb(); /* Ensure update-side operation before counter increment. */
76 WARN_ON_ONCE(!(*sp & 0x1));
77 WRITE_ONCE(*sp, *sp + 1);
80 /* Take a snapshot of the update side's sequence number. */
81 static inline unsigned long rcu_seq_snap(unsigned long *sp)
85 s = (READ_ONCE(*sp) + 3) & ~0x1;
86 smp_mb(); /* Above access must not bleed into critical section. */
90 /* Return the current value the update side's sequence number, no ordering. */
91 static inline unsigned long rcu_seq_current(unsigned long *sp)
93 return READ_ONCE(*sp);
97 * Given a snapshot from rcu_seq_snap(), determine whether or not a
98 * full update-side operation has occurred.
100 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
102 return ULONG_CMP_GE(READ_ONCE(*sp), s);
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.
111 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
112 # define STATE_RCU_HEAD_READY 0
113 # define STATE_RCU_HEAD_QUEUED 1
115 extern struct debug_obj_descr rcuhead_debug_descr;
117 static inline int debug_rcu_head_queue(struct rcu_head *head)
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);
128 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
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);
135 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
136 static inline int debug_rcu_head_queue(struct rcu_head *head)
141 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
144 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
146 void kfree(const void *);
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.
152 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
154 unsigned long offset = (unsigned long)head->func;
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);
163 RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
165 rcu_lock_release(&rcu_callback_map);
170 #ifdef CONFIG_RCU_STALL_COMMON
172 extern int rcu_cpu_stall_suppress;
173 int rcu_jiffies_till_stall_check(void);
175 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
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.
182 #define TPS(x) tracepoint_string(x)
184 void rcu_early_boot_tests(void);
185 void rcu_test_sync_prims(void);
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.
191 extern void resched_cpu(int cpu);
193 #if defined(SRCU) || !defined(TINY_RCU)
195 #include <linux/rcu_node_tree.h>
197 extern int rcu_num_lvls;
198 extern int rcu_num_nodes;
199 static bool rcu_fanout_exact;
200 static int rcu_fanout_leaf;
203 * Compute the per-level fanout, either using the exact fanout specified
204 * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
206 static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
210 if (rcu_fanout_exact) {
211 levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
212 for (i = rcu_num_lvls - 2; i >= 0; i--)
213 levelspread[i] = RCU_FANOUT;
219 for (i = rcu_num_lvls - 1; i >= 0; i--) {
221 levelspread[i] = (cprv + ccur - 1) / ccur;
228 * Do a full breadth-first scan of the rcu_node structures for the
229 * specified rcu_state structure.
231 #define rcu_for_each_node_breadth_first(rsp, rnp) \
232 for ((rnp) = &(rsp)->node[0]; \
233 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
236 * Do a breadth-first scan of the non-leaf rcu_node structures for the
237 * specified rcu_state structure. Note that if there is a singleton
238 * rcu_node tree with but one rcu_node structure, this loop is a no-op.
240 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
241 for ((rnp) = &(rsp)->node[0]; \
242 (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)
245 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
246 * structure. Note that if there is a singleton rcu_node tree with but
247 * one rcu_node structure, this loop -will- visit the rcu_node structure.
248 * It is still a leaf node, even if it is also the root node.
250 #define rcu_for_each_leaf_node(rsp, rnp) \
251 for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
252 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
255 * Iterate over all possible CPUs in a leaf RCU node.
257 #define for_each_leaf_node_possible_cpu(rnp, cpu) \
258 for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \
260 cpu = cpumask_next((cpu), cpu_possible_mask))
262 #endif /* #if defined(SRCU) || !defined(TINY_RCU) */
264 #endif /* __LINUX_RCU_H */