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 */
rcu_virt_note_context_switch(void)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
38 void rcu_barrier(void);
39 void rcu_momentary_eqs(void);
40
41 struct 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 */
same_state_synchronize_rcu_full(struct rcu_gp_oldstate * rgosp1,struct rcu_gp_oldstate * rgosp2)68 static 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
74 unsigned long start_poll_synchronize_rcu_expedited(void);
75 void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
76 void cond_synchronize_rcu_expedited(unsigned long oldstate);
77 void cond_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp);
78 unsigned long get_state_synchronize_rcu(void);
79 void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
80 unsigned long start_poll_synchronize_rcu(void);
81 void start_poll_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
82 bool poll_state_synchronize_rcu(unsigned long oldstate);
83 bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
84 void cond_synchronize_rcu(unsigned long oldstate);
85 void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
86
87 #ifdef CONFIG_PROVE_RCU
88 void rcu_irq_exit_check_preempt(void);
89 #else
rcu_irq_exit_check_preempt(void)90 static inline void rcu_irq_exit_check_preempt(void) { }
91 #endif
92
93 struct task_struct;
94 void rcu_preempt_deferred_qs(struct task_struct *t);
95
96 void exit_rcu(void);
97
98 void rcu_scheduler_starting(void);
99 extern int rcu_scheduler_active;
100 void rcu_end_inkernel_boot(void);
101 bool rcu_inkernel_boot_has_ended(void);
102 bool rcu_is_watching(void);
103 #ifndef CONFIG_PREEMPT_RCU
104 void rcu_all_qs(void);
105 #endif
106
107 /* RCUtree hotplug events */
108 int rcutree_prepare_cpu(unsigned int cpu);
109 int rcutree_online_cpu(unsigned int cpu);
110 void rcutree_report_cpu_starting(unsigned int cpu);
111
112 #ifdef CONFIG_HOTPLUG_CPU
113 int rcutree_dead_cpu(unsigned int cpu);
114 int rcutree_dying_cpu(unsigned int cpu);
115 int 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
122 void rcutree_migrate_callbacks(int cpu);
123
124 /* Called from hotplug and also arm64 early secondary boot failure */
125 void rcutree_report_cpu_dead(void);
126
127 #endif /* __LINUX_RCUTREE_H */
128