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
20 void rcu_softirq_qs(void);
21 void rcu_note_context_switch(bool preempt);
22 int rcu_needs_cpu(void);
23 void rcu_cpu_stall_reset(void);
24 void 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 */
31 static inline void rcu_virt_note_context_switch(void)
32 {
33 rcu_note_context_switch(false);
34 }
35
36 void synchronize_rcu_expedited(void);
37 void kvfree_call_rcu(struct rcu_head *head, void *ptr);
38
39 void rcu_barrier(void);
40 void rcu_momentary_dyntick_idle(void);
41 void kfree_rcu_scheduler_running(void);
42 bool rcu_gp_might_be_stalled(void);
43
44 struct rcu_gp_oldstate {
45 unsigned long rgos_norm;
46 unsigned long rgos_exp;
47 };
48
49 // Maximum number of rcu_gp_oldstate values corresponding to
50 // not-yet-completed RCU grace periods.
51 #define NUM_ACTIVE_RCU_POLL_FULL_OLDSTATE 4
52
53 /**
54 * same_state_synchronize_rcu_full - Are two old-state values identical?
55 * @rgosp1: First old-state value.
56 * @rgosp2: Second old-state value.
57 *
58 * The two old-state values must have been obtained from either
59 * get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(),
60 * or get_completed_synchronize_rcu_full(). Returns @true if the two
61 * values are identical and @false otherwise. This allows structures
62 * whose lifetimes are tracked by old-state values to push these values
63 * to a list header, allowing those structures to be slightly smaller.
64 *
65 * Note that equality is judged on a bitwise basis, so that an
66 * @rcu_gp_oldstate structure with an already-completed state in one field
67 * will compare not-equal to a structure with an already-completed state
68 * in the other field. After all, the @rcu_gp_oldstate structure is opaque
69 * so how did such a situation come to pass in the first place?
70 */
71 static inline bool same_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp1,
72 struct rcu_gp_oldstate *rgosp2)
73 {
74 return rgosp1->rgos_norm == rgosp2->rgos_norm && rgosp1->rgos_exp == rgosp2->rgos_exp;
75 }
76
77 unsigned long start_poll_synchronize_rcu_expedited(void);
78 void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
79 void cond_synchronize_rcu_expedited(unsigned long oldstate);
80 void cond_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
81 unsigned long get_state_synchronize_rcu(void);
82 void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
83 unsigned long start_poll_synchronize_rcu(void);
84 void start_poll_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
85 bool poll_state_synchronize_rcu(unsigned long oldstate);
86 bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
87 void cond_synchronize_rcu(unsigned long oldstate);
88 void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
89
90 #ifdef CONFIG_PROVE_RCU
91 void rcu_irq_exit_check_preempt(void);
92 #else
93 static inline void rcu_irq_exit_check_preempt(void) { }
94 #endif
95
96 struct task_struct;
97 void rcu_preempt_deferred_qs(struct task_struct *t);
98
99 void exit_rcu(void);
100
101 void rcu_scheduler_starting(void);
102 extern int rcu_scheduler_active;
103 void rcu_end_inkernel_boot(void);
104 bool rcu_inkernel_boot_has_ended(void);
105 bool rcu_is_watching(void);
106 #ifndef CONFIG_PREEMPTION
107 void rcu_all_qs(void);
108 #endif
109
110 /* RCUtree hotplug events */
111 int rcutree_prepare_cpu(unsigned int cpu);
112 int rcutree_online_cpu(unsigned int cpu);
113 void rcutree_report_cpu_starting(unsigned int cpu);
114
115 #ifdef CONFIG_HOTPLUG_CPU
116 int rcutree_dead_cpu(unsigned int cpu);
117 int rcutree_dying_cpu(unsigned int cpu);
118 int rcutree_offline_cpu(unsigned int cpu);
119 #else
120 #define rcutree_dead_cpu NULL
121 #define rcutree_dying_cpu NULL
122 #define rcutree_offline_cpu NULL
123 #endif
124
125 void rcutree_migrate_callbacks(int cpu);
126
127 /* Called from hotplug and also arm64 early secondary boot failure */
128 void rcutree_report_cpu_dead(void);
129
130 #endif /* __LINUX_RCUTREE_H */
131
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