1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Sleepable Read-Copy Update mechanism for mutual exclusion, 4 * tiny variant. 5 * 6 * Copyright (C) IBM Corporation, 2017 7 * 8 * Author: Paul McKenney <paulmck@linux.ibm.com> 9 */ 10 11 #ifndef _LINUX_SRCU_TINY_H 12 #define _LINUX_SRCU_TINY_H 13 14 #include <linux/irq_work_types.h> 15 #include <linux/swait.h> 16 17 struct srcu_struct { 18 short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */ 19 u8 srcu_gp_running; /* GP workqueue running? */ 20 u8 srcu_gp_waiting; /* GP waiting for readers? */ 21 unsigned long srcu_idx; /* Current reader array element in bit 0x2. */ 22 unsigned long srcu_idx_max; /* Furthest future srcu_idx request. */ 23 struct swait_queue_head srcu_wq; 24 /* Last srcu_read_unlock() wakes GP. */ 25 struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ 26 struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ 27 struct work_struct srcu_work; /* For driving grace periods. */ 28 struct irq_work srcu_irq_work; /* Defer schedule_work() to irq work. */ 29 #ifdef CONFIG_DEBUG_LOCK_ALLOC 30 struct lockdep_map dep_map; 31 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 32 }; 33 34 void srcu_drive_gp(struct work_struct *wp); 35 void srcu_tiny_irq_work(struct irq_work *irq_work); 36 37 #define __SRCU_STRUCT_INIT(name, __ignored, ___ignored, ____ignored) \ 38 { \ 39 .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ 40 .srcu_cb_tail = &name.srcu_cb_head, \ 41 .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ 42 .srcu_irq_work = { .func = srcu_tiny_irq_work }, \ 43 __SRCU_DEP_MAP_INIT(name) \ 44 } 45 46 /* 47 * This odd _STATIC_ arrangement is needed for API compatibility with 48 * Tree SRCU, which needs some per-CPU data. 49 */ 50 #define DEFINE_SRCU(name) \ 51 struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name) 52 #define DEFINE_STATIC_SRCU(name) \ 53 static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name) 54 #define DEFINE_SRCU_FAST(name) DEFINE_SRCU(name) 55 #define DEFINE_STATIC_SRCU_FAST(name) \ 56 static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name) 57 #define DEFINE_SRCU_FAST_UPDOWN(name) DEFINE_SRCU(name) 58 #define DEFINE_STATIC_SRCU_FAST_UPDOWN(name) \ 59 static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name) 60 61 // Dummy structure for srcu_notifier_head. 62 struct srcu_usage { }; 63 #define __SRCU_USAGE_INIT(name) { } 64 #define __init_srcu_struct_fast __init_srcu_struct 65 #define __init_srcu_struct_fast_updown __init_srcu_struct 66 #ifndef CONFIG_DEBUG_LOCK_ALLOC 67 #define init_srcu_struct_fast init_srcu_struct 68 #define init_srcu_struct_fast_updown init_srcu_struct 69 #endif // #ifndef CONFIG_DEBUG_LOCK_ALLOC 70 71 void synchronize_srcu(struct srcu_struct *ssp); 72 73 /* 74 * Counts the new reader in the appropriate per-CPU element of the 75 * srcu_struct. Can be invoked from irq/bh handlers, but the matching 76 * __srcu_read_unlock() must be in the same handler instance. Returns an 77 * index that must be passed to the matching srcu_read_unlock(). 78 */ 79 static inline int __srcu_read_lock(struct srcu_struct *ssp) 80 __acquires_shared(ssp) 81 { 82 int idx; 83 84 preempt_disable(); // Needed for PREEMPT_LAZY 85 idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1; 86 WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1); 87 preempt_enable(); 88 __acquire_shared(ssp); 89 return idx; 90 } 91 92 struct srcu_ctr; 93 94 static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __percpu *scpp) 95 { 96 return (int)(intptr_t)(struct srcu_ctr __force __kernel *)scpp; 97 } 98 99 static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ssp, int idx) 100 { 101 return (struct srcu_ctr __percpu *)(intptr_t)idx; 102 } 103 104 static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp) 105 __acquires_shared(ssp) 106 { 107 return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp)); 108 } 109 110 static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) 111 __releases_shared(ssp) 112 { 113 __srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp)); 114 } 115 116 static inline struct srcu_ctr __percpu *__srcu_read_lock_fast_updown(struct srcu_struct *ssp) 117 __acquires_shared(ssp) 118 { 119 return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp)); 120 } 121 122 static inline 123 void __srcu_read_unlock_fast_updown(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) 124 __releases_shared(ssp) 125 { 126 __srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp)); 127 } 128 129 static inline void synchronize_srcu_expedited(struct srcu_struct *ssp) 130 { 131 synchronize_srcu(ssp); 132 } 133 134 static inline void srcu_barrier(struct srcu_struct *ssp) 135 { 136 synchronize_srcu(ssp); 137 } 138 139 static inline void srcu_expedite_current(struct srcu_struct *ssp) { } 140 #define srcu_check_read_flavor(ssp, read_flavor) do { } while (0) 141 142 /* Defined here to avoid size increase for non-torture kernels. */ 143 static inline void srcu_torture_stats_print(struct srcu_struct *ssp, 144 char *tt, char *tf) 145 { 146 int idx; 147 148 idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1; 149 pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd) gp: %lu->%lu\n", 150 tt, tf, idx, 151 data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])), 152 data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])), 153 data_race(READ_ONCE(ssp->srcu_idx)), 154 data_race(READ_ONCE(ssp->srcu_idx_max))); 155 } 156 157 #endif 158