LXR linux/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
  17unsigned long get_state_synchronize_rcu(void);
  18unsigned long start_poll_synchronize_rcu(void);
  19bool poll_state_synchronize_rcu(unsigned long oldstate);
  20
  21static inline void cond_synchronize_rcu(unsigned long oldstate)
  22{
  23        might_sleep();
  24}
  25
  26extern void rcu_barrier(void);
  27
  28static inline void synchronize_rcu_expedited(void)
  29{
  30        synchronize_rcu();
  31}
  32
  33/*
  34 * Add one more declaration of kvfree() here. It is
  35 * not so straight forward to just include <linux/mm.h>
  36 * where it is defined due to getting many compile
  37 * errors caused by that include.
  38 */
  39extern void kvfree(const void *addr);
  40
  41static inline void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
  42{
  43        if (head) {
  44                call_rcu(head, func);
  45                return;
  46        }
  47
  48        // kvfree_rcu(one_arg) call.
  49        might_sleep();
  50        synchronize_rcu();
  51        kvfree((void *) func);
  52}
  53
  54void rcu_qs(void);
  55
  56static inline void rcu_softirq_qs(void)
  57{
  58        rcu_qs();
  59}
  60
  61#define rcu_note_context_switch(preempt) \
  62        do { \
  63                rcu_qs(); \
  64                rcu_tasks_qs(current, (preempt)); \
  65        } while (0)
  66
  67static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt)
  68{
  69        *nextevt = KTIME_MAX;
  70        return 0;
  71}
  72
  73/*
  74 * Take advantage of the fact that there is only one CPU, which
  75 * allows us to ignore virtualization-based context switches.
  76 */
  77static inline void rcu_virt_note_context_switch(int cpu) { }
  78static inline void rcu_cpu_stall_reset(void) { }
  79static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
  80static inline void rcu_idle_enter(void) { }
  81static inline void rcu_idle_exit(void) { }
  82static inline void rcu_irq_enter(void) { }
  83static inline void rcu_irq_exit_irqson(void) { }
  84static inline void rcu_irq_enter_irqson(void) { }
  85static inline void rcu_irq_exit(void) { }
  86static inline void rcu_irq_exit_check_preempt(void) { }
  87#define rcu_is_idle_cpu(cpu) \
  88        (is_idle_task(current) && !in_nmi() && !in_irq() && !in_serving_softirq())
  89static inline void exit_rcu(void) { }
  90static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
  91{
  92        return false;
  93}
  94static inline void rcu_preempt_deferred_qs(struct task_struct *t) { }
  95#ifdef CONFIG_SRCU
  96void rcu_scheduler_starting(void);
  97#else /* #ifndef CONFIG_SRCU */
  98static inline void rcu_scheduler_starting(void) { }
  99#endif /* #else #ifndef CONFIG_SRCU */
 100static inline void rcu_end_inkernel_boot(void) { }
 101static inline bool rcu_inkernel_boot_has_ended(void) { return true; }
 102static inline bool rcu_is_watching(void) { return true; }
 103static inline void rcu_momentary_dyntick_idle(void) { }
 104static inline void kfree_rcu_scheduler_running(void) { }
 105static inline bool rcu_gp_might_be_stalled(void) { return false; }
 106
 107/* Avoid RCU read-side critical sections leaking across. */
 108static inline void rcu_all_qs(void) { barrier(); }
 109
 110/* RCUtree hotplug events */
 111#define rcutree_prepare_cpu      NULL
 112#define rcutree_online_cpu       NULL
 113#define rcutree_offline_cpu      NULL
 114#define rcutree_dead_cpu         NULL
 115#define rcutree_dying_cpu        NULL
 116static inline void rcu_cpu_starting(unsigned int cpu) { }
 117
 118#endif /* __LINUX_RCUTINY_H */
 119