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 <[email protected]> 8 * Paul E. McKenney <[email protected]> Hierarchical algorithm 9 * 10 * Based on the original work by Paul McKenney <[email protected]> 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 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 */ 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 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