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. */
91 * Given a snapshot from rcu_seq_snap(), determine whether or not a
92 * full update-side operation has occurred.
94 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
96 return ULONG_CMP_GE(READ_ONCE(*sp), s);
100 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
101 * by call_rcu() and rcu callback execution, and are therefore not part of the
102 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
105 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
106 # define STATE_RCU_HEAD_READY 0
107 # define STATE_RCU_HEAD_QUEUED 1
109 extern struct debug_obj_descr rcuhead_debug_descr;
111 static inline int debug_rcu_head_queue(struct rcu_head *head)
115 r1 = debug_object_activate(head, &rcuhead_debug_descr);
116 debug_object_active_state(head, &rcuhead_debug_descr,
117 STATE_RCU_HEAD_READY,
118 STATE_RCU_HEAD_QUEUED);
122 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
124 debug_object_active_state(head, &rcuhead_debug_descr,
125 STATE_RCU_HEAD_QUEUED,
126 STATE_RCU_HEAD_READY);
127 debug_object_deactivate(head, &rcuhead_debug_descr);
129 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
130 static inline int debug_rcu_head_queue(struct rcu_head *head)
135 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
138 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
140 void kfree(const void *);
143 * Reclaim the specified callback, either by invoking it (non-lazy case)
144 * or freeing it directly (lazy case). Return true if lazy, false otherwise.
146 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
148 unsigned long offset = (unsigned long)head->func;
150 rcu_lock_acquire(&rcu_callback_map);
151 if (__is_kfree_rcu_offset(offset)) {
152 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
153 kfree((void *)head - offset);
154 rcu_lock_release(&rcu_callback_map);
157 RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
159 rcu_lock_release(&rcu_callback_map);
164 #ifdef CONFIG_RCU_STALL_COMMON
166 extern int rcu_cpu_stall_suppress;
167 int rcu_jiffies_till_stall_check(void);
169 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
172 * Strings used in tracepoints need to be exported via the
173 * tracing system such that tools like perf and trace-cmd can
174 * translate the string address pointers to actual text.
176 #define TPS(x) tracepoint_string(x)
178 void rcu_early_boot_tests(void);
179 void rcu_test_sync_prims(void);
182 * This function really isn't for public consumption, but RCU is special in
183 * that context switches can allow the state machine to make progress.
185 extern void resched_cpu(int cpu);
187 #endif /* __LINUX_RCU_H */