include/linux/rcutree.h

   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 void kvfree_rcu_barrier(void);
  39
  40 void rcu_barrier(void);
  41 void rcu_momentary_eqs(void);
  42 void kfree_rcu_scheduler_running(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 */