include/linux/rcutiny.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
   4  *
   5  * Copyright IBM Corporation, 2008
   6  *
   7  * Author: Paul E. McKenney <paulmck@linux.ibm.com>
   8  *
   9  * For detailed explanation of Read-Copy Update mechanism see -
  10  *              Documentation/RCU
  11  */
  12 #ifndef __LINUX_TINY_H
  13 #define __LINUX_TINY_H
  14
  15 #include <asm/param.h> /* for HZ */
  16
  17 /* Never flag non-existent other CPUs! */
  18 static inline bool rcu_eqs_special_set(int cpu) { return false; }
  19
  20 static inline unsigned long get_state_synchronize_rcu(void)
  21 {
  22         return 0;
  23 }
  24
  25 static inline void cond_synchronize_rcu(unsigned long oldstate)
  26 {
  27         might_sleep();
  28 }
  29
  30 extern void rcu_barrier(void);
  31
  32 static inline void synchronize_rcu_expedited(void)
  33 {
  34         synchronize_rcu();
  35 }
  36
  37 /*
  38  * Add one more declaration of kvfree() here. It is
  39  * not so straight forward to just include <linux/mm.h>
  40  * where it is defined due to getting many compile
  41  * errors caused by that include.
  42  */
  43 extern void kvfree(const void *addr);
  44
  45 static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
  46 {
  47         if (head) {
  48                 call_rcu(head, func);
  49                 return;
  50         }
  51
  52         // kvfree_rcu(one_arg) call.
  53         might_sleep();
  54         synchronize_rcu();
  55         kvfree((void *) func);
  56 }
  57
  58 void rcu_qs(void);
  59
  60 static inline void rcu_softirq_qs(void)
  61 {
  62         rcu_qs();
  63 }
  64
  65 #define rcu_note_context_switch(preempt) \
  66         do { \
  67                 rcu_qs(); \
  68                 rcu_tasks_qs(current, (preempt)); \
  69         } while (0)
  70
  71 static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt)
  72 {
  73         *nextevt = KTIME_MAX;
  74         return 0;
  75 }
  76
  77 /*
  78  * Take advantage of the fact that there is only one CPU, which
  79  * allows us to ignore virtualization-based context switches.
  80  */
  81 static inline void rcu_virt_note_context_switch(int cpu) { }
  82 static inline void rcu_cpu_stall_reset(void) { }
  83 static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
  84 static inline void rcu_idle_enter(void) { }
  85 static inline void rcu_idle_exit(void) { }
  86 static inline void rcu_irq_enter(void) { }
  87 static inline void rcu_irq_exit_irqson(void) { }
  88 static inline void rcu_irq_enter_irqson(void) { }
  89 static inline void rcu_irq_exit(void) { }
  90 static inline void rcu_irq_exit_preempt(void) { }
  91 static inline void rcu_irq_exit_check_preempt(void) { }
  92 static inline void exit_rcu(void) { }
  93 static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
  94 {
  95         return false;
  96 }
  97 static inline void rcu_preempt_deferred_qs(struct task_struct *t) { }
  98 #ifdef CONFIG_SRCU
  99 void rcu_scheduler_starting(void);
 100 #else /* #ifndef CONFIG_SRCU */
 101 static inline void rcu_scheduler_starting(void) { }
 102 #endif /* #else #ifndef CONFIG_SRCU */
 103 static inline void rcu_end_inkernel_boot(void) { }
 104 static inline bool rcu_inkernel_boot_has_ended(void) { return true; }
 105 static inline bool rcu_is_watching(void) { return true; }
 106 static inline bool __rcu_is_watching(void) { return true; }
 107 static inline void rcu_momentary_dyntick_idle(void) { }
 108 static inline void kfree_rcu_scheduler_running(void) { }
 109 static inline bool rcu_gp_might_be_stalled(void) { return false; }
 110
 111 /* Avoid RCU read-side critical sections leaking across. */
 112 static inline void rcu_all_qs(void) { barrier(); }
 113
 114 /* RCUtree hotplug events */
 115 #define rcutree_prepare_cpu      NULL
 116 #define rcutree_online_cpu       NULL
 117 #define rcutree_offline_cpu      NULL
 118 #define rcutree_dead_cpu         NULL
 119 #define rcutree_dying_cpu        NULL
 120 static inline void rcu_cpu_starting(unsigned int cpu) { }
 121
 122 #endif /* __LINUX_RCUTINY_H */