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 #define rcu_is_idle_cpu(cpu) \ 93 (is_idle_task(current) && !in_nmi() && !in_irq() && !in_serving_softirq()) 94 static inline void exit_rcu(void) { } 95 static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t) 96 { 97 return false; 98 } 99 static inline void rcu_preempt_deferred_qs(struct task_struct *t) { } 100 #ifdef CONFIG_SRCU 101 void rcu_scheduler_starting(void); 102 #else /* #ifndef CONFIG_SRCU */ 103 static inline void rcu_scheduler_starting(void) { } 104 #endif /* #else #ifndef CONFIG_SRCU */ 105 static inline void rcu_end_inkernel_boot(void) { } 106 static inline bool rcu_inkernel_boot_has_ended(void) { return true; } 107 static inline bool rcu_is_watching(void) { return true; } 108 static inline void rcu_momentary_dyntick_idle(void) { } 109 static inline void kfree_rcu_scheduler_running(void) { } 110 static inline bool rcu_gp_might_be_stalled(void) { return false; } 111 112 /* Avoid RCU read-side critical sections leaking across. */ 113 static inline void rcu_all_qs(void) { barrier(); } 114 115 /* RCUtree hotplug events */ 116 #define rcutree_prepare_cpu NULL 117 #define rcutree_online_cpu NULL 118 #define rcutree_offline_cpu NULL 119 #define rcutree_dead_cpu NULL 120 #define rcutree_dying_cpu NULL 121 static inline void rcu_cpu_starting(unsigned int cpu) { } 122 123 #endif /* __LINUX_RCUTINY_H */ 124