1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Sleepable Read-Copy Update mechanism for mutual exclusion, 4 * tree variant. 5 * 6 * Copyright (C) IBM Corporation, 2017 7 * 8 * Author: Paul McKenney <paulmck@linux.ibm.com> 9 */ 10 11 #ifndef _LINUX_SRCU_TREE_H 12 #define _LINUX_SRCU_TREE_H 13 14 #include <linux/rcu_node_tree.h> 15 #include <linux/completion.h> 16 17 struct srcu_node; 18 struct srcu_struct; 19 20 /* 21 * Per-CPU structure feeding into leaf srcu_node, similar in function 22 * to rcu_node. 23 */ 24 struct srcu_data { 25 /* Read-side state. */ 26 unsigned long srcu_lock_count[2]; /* Locks per CPU. */ 27 unsigned long srcu_unlock_count[2]; /* Unlocks per CPU. */ 28 29 /* Update-side state. */ 30 spinlock_t __private lock ____cacheline_internodealigned_in_smp; 31 struct rcu_segcblist srcu_cblist; /* List of callbacks.*/ 32 unsigned long srcu_gp_seq_needed; /* Furthest future GP needed. */ 33 unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ 34 bool srcu_cblist_invoking; /* Invoking these CBs? */ 35 struct timer_list delay_work; /* Delay for CB invoking */ 36 struct work_struct work; /* Context for CB invoking. */ 37 struct rcu_head srcu_barrier_head; /* For srcu_barrier() use. */ 38 struct srcu_node *mynode; /* Leaf srcu_node. */ 39 unsigned long grpmask; /* Mask for leaf srcu_node */ 40 /* ->srcu_data_have_cbs[]. */ 41 int cpu; 42 struct srcu_struct *ssp; 43 }; 44 45 /* 46 * Node in SRCU combining tree, similar in function to rcu_data. 47 */ 48 struct srcu_node { 49 spinlock_t __private lock; 50 unsigned long srcu_have_cbs[4]; /* GP seq for children having CBs, but only */ 51 /* if greater than ->srcu_gq_seq. */ 52 unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs have CBs for given GP? */ 53 unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ 54 struct srcu_node *srcu_parent; /* Next up in tree. */ 55 int grplo; /* Least CPU for node. */ 56 int grphi; /* Biggest CPU for node. */ 57 }; 58 59 /* 60 * Per-SRCU-domain structure, similar in function to rcu_state. 61 */ 62 struct srcu_struct { 63 struct srcu_node *node; /* Combining tree. */ 64 struct srcu_node *level[RCU_NUM_LVLS + 1]; 65 /* First node at each level. */ 66 int srcu_size_state; /* Small-to-big transition state. */ 67 struct mutex srcu_cb_mutex; /* Serialize CB preparation. */ 68 spinlock_t __private lock; /* Protect counters and size state. */ 69 struct mutex srcu_gp_mutex; /* Serialize GP work. */ 70 unsigned int srcu_idx; /* Current rdr array element. */ 71 unsigned long srcu_gp_seq; /* Grace-period seq #. */ 72 unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */ 73 unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ 74 unsigned long srcu_gp_start; /* Last GP start timestamp (jiffies) */ 75 unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */ 76 unsigned long srcu_size_jiffies; /* Current contention-measurement interval. */ 77 unsigned long srcu_n_lock_retries; /* Contention events in current interval. */ 78 unsigned long srcu_n_exp_nodelay; /* # expedited no-delays in current GP phase. */ 79 struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ 80 bool sda_is_static; /* May ->sda be passed to free_percpu()? */ 81 unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ 82 struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */ 83 struct completion srcu_barrier_completion; 84 /* Awaken barrier rq at end. */ 85 atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */ 86 /* callback for the barrier */ 87 /* operation. */ 88 unsigned long reschedule_jiffies; 89 unsigned long reschedule_count; 90 struct delayed_work work; 91 struct lockdep_map dep_map; 92 }; 93 94 /* Values for size state variable (->srcu_size_state). */ 95 #define SRCU_SIZE_SMALL 0 96 #define SRCU_SIZE_ALLOC 1 97 #define SRCU_SIZE_WAIT_BARRIER 2 98 #define SRCU_SIZE_WAIT_CALL 3 99 #define SRCU_SIZE_WAIT_CBS1 4 100 #define SRCU_SIZE_WAIT_CBS2 5 101 #define SRCU_SIZE_WAIT_CBS3 6 102 #define SRCU_SIZE_WAIT_CBS4 7 103 #define SRCU_SIZE_BIG 8 104 105 /* Values for state variable (bottom bits of ->srcu_gp_seq). */ 106 #define SRCU_STATE_IDLE 0 107 #define SRCU_STATE_SCAN1 1 108 #define SRCU_STATE_SCAN2 2 109 110 #define __SRCU_STRUCT_INIT(name, pcpu_name) \ 111 { \ 112 .sda = &pcpu_name, \ 113 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 114 .srcu_gp_seq_needed = -1UL, \ 115 .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ 116 __SRCU_DEP_MAP_INIT(name) \ 117 } 118 119 /* 120 * Define and initialize a srcu struct at build time. 121 * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it. 122 * 123 * Note that although DEFINE_STATIC_SRCU() hides the name from other 124 * files, the per-CPU variable rules nevertheless require that the 125 * chosen name be globally unique. These rules also prohibit use of 126 * DEFINE_STATIC_SRCU() within a function. If these rules are too 127 * restrictive, declare the srcu_struct manually. For example, in 128 * each file: 129 * 130 * static struct srcu_struct my_srcu; 131 * 132 * Then, before the first use of each my_srcu, manually initialize it: 133 * 134 * init_srcu_struct(&my_srcu); 135 * 136 * See include/linux/percpu-defs.h for the rules on per-CPU variables. 137 */ 138 #ifdef MODULE 139 # define __DEFINE_SRCU(name, is_static) \ 140 is_static struct srcu_struct name; \ 141 extern struct srcu_struct * const __srcu_struct_##name; \ 142 struct srcu_struct * const __srcu_struct_##name \ 143 __section("___srcu_struct_ptrs") = &name 144 #else 145 # define __DEFINE_SRCU(name, is_static) \ 146 static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \ 147 is_static struct srcu_struct name = \ 148 __SRCU_STRUCT_INIT(name, name##_srcu_data) 149 #endif 150 #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) 151 #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) 152 153 void synchronize_srcu_expedited(struct srcu_struct *ssp); 154 void srcu_barrier(struct srcu_struct *ssp); 155 void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); 156 157 #endif 158