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 
25 /*
26  * Note a virtualization-based context switch.  This is simply a
27  * wrapper around rcu_note_context_switch(), which allows TINY_RCU
28  * to save a few bytes. The caller must have disabled interrupts.
29  */
rcu_virt_note_context_switch(void)30 static inline void rcu_virt_note_context_switch(void)
31 {
32 	rcu_note_context_switch(false);
33 }
34 
35 void synchronize_rcu_expedited(void);
36 void kvfree_call_rcu(struct rcu_head *head, void *ptr);
37 
38 void rcu_barrier(void);
39 bool rcu_eqs_special_set(int cpu);
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  */
same_state_synchronize_rcu_full(struct rcu_gp_oldstate * rgosp1,struct rcu_gp_oldstate * rgosp2)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
rcu_irq_exit_check_preempt(void)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 int rcutree_offline_cpu(unsigned int cpu);
114 int rcutree_dead_cpu(unsigned int cpu);
115 int rcutree_dying_cpu(unsigned int cpu);
116 void rcu_cpu_starting(unsigned int cpu);
117 
118 #endif /* __LINUX_RCUTREE_H */
119