1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
4 *
5 * Copyright IBM Corporation, 2008
6 *
7 * Author: Dipankar Sarma <dipankar@in.ibm.com>
8 * Paul E. McKenney <paulmck@linux.ibm.com> Hierarchical algorithm
9 *
10 * Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
11 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
12 *
13 * For detailed explanation of Read-Copy Update mechanism see -
14 * Documentation/RCU
15 */
16
17#ifndef __LINUX_RCUTREE_H
18#define __LINUX_RCUTREE_H
19
20void rcu_softirq_qs(void);
21void rcu_note_context_switch(bool preempt);
22int rcu_needs_cpu(void);
23void rcu_cpu_stall_reset(void);
24void rcu_request_urgent_qs_task(struct task_struct *t);
25
26/*
27 * Note a virtualization-based context switch. This is simply a
28 * wrapper around rcu_note_context_switch(), which allows TINY_RCU
29 * to save a few bytes. The caller must have disabled interrupts.
30 */
31static inline void rcu_virt_note_context_switch(void)
32{
33 rcu_note_context_switch(preempt: false);
34}
35
36void synchronize_rcu_expedited(void);
37
38void rcu_barrier(void);
39void rcu_momentary_eqs(void);
40
41struct rcu_gp_oldstate {
42 unsigned long rgos_norm;
43 unsigned long rgos_exp;
44};
45
46// Maximum number of rcu_gp_oldstate values corresponding to
47// not-yet-completed RCU grace periods.
48#define NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE 4
49
50/**
51 * same_state_synchronize_rcu_full - Are two old-state values identical?
52 * @rgosp1: First old-state value.
53 * @rgosp2: Second old-state value.
54 *
55 * The two old-state values must have been obtained from either
56 * get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(),
57 * or get_completed_synchronize_rcu_full(). Returns @true if the two
58 * values are identical and @false otherwise. This allows structures
59 * whose lifetimes are tracked by old-state values to push these values
60 * to a list header, allowing those structures to be slightly smaller.
61 *
62 * Note that equality is judged on a bitwise basis, so that an
63 * @rcu_gp_oldstate structure with an already-completed state in one field
64 * will compare not-equal to a structure with an already-completed state
65 * in the other field. After all, the @rcu_gp_oldstate structure is opaque
66 * so how did such a situation come to pass in the first place?
67 */
68static inline bool same_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp1,
69 struct rcu_gp_oldstate *rgosp2)
70{
71 return rgosp1->rgos_norm == rgosp2->rgos_norm && rgosp1->rgos_exp == rgosp2->rgos_exp;
72}
73
74unsigned long start_poll_synchronize_rcu_expedited(void);
75void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
76void cond_synchronize_rcu_expedited(unsigned long oldstate);
77void cond_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
78unsigned long get_state_synchronize_rcu(void);
79void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
80unsigned long start_poll_synchronize_rcu(void);
81void start_poll_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
82bool poll_state_synchronize_rcu(unsigned long oldstate);
83bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
84void cond_synchronize_rcu(unsigned long oldstate);
85void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
86
87#ifdef CONFIG_PROVE_RCU
88void rcu_irq_exit_check_preempt(void);
89#else
90static inline void rcu_irq_exit_check_preempt(void) { }
91#endif
92
93struct task_struct;
94void rcu_preempt_deferred_qs(struct task_struct *t);
95
96void exit_rcu(void);
97
98void rcu_scheduler_starting(void);
99extern int rcu_scheduler_active;
100void rcu_end_inkernel_boot(void);
101bool rcu_inkernel_boot_has_ended(void);
102bool rcu_is_watching(void);
103#ifndef CONFIG_PREEMPT_RCU
104void rcu_all_qs(void);
105#endif
106
107/* RCUtree hotplug events */
108int rcutree_prepare_cpu(unsigned int cpu);
109int rcutree_online_cpu(unsigned int cpu);
110void rcutree_report_cpu_starting(unsigned int cpu);
111
112#ifdef CONFIG_HOTPLUG_CPU
113int rcutree_dead_cpu(unsigned int cpu);
114int rcutree_dying_cpu(unsigned int cpu);
115int rcutree_offline_cpu(unsigned int cpu);
116#else
117#define rcutree_dead_cpu NULL
118#define rcutree_dying_cpu NULL
119#define rcutree_offline_cpu NULL
120#endif
121
122void rcutree_migrate_callbacks(int cpu);
123
124/* Called from hotplug and also arm64 early secondary boot failure */
125void rcutree_report_cpu_dead(void);
126
127#endif /* __LINUX_RCUTREE_H */
128