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 atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */ 27 atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */ 28 int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */ 29 30 /* Update-side state. */ 31 spinlock_t __private lock ____cacheline_internodealigned_in_smp; 32 struct rcu_segcblist srcu_cblist; /* List of callbacks.*/ 33 unsigned long srcu_gp_seq_needed; /* Furthest future GP needed. */ 34 unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ 35 bool srcu_cblist_invoking; /* Invoking these CBs? */ 36 struct timer_list delay_work; /* Delay for CB invoking */ 37 struct work_struct work; /* Context for CB invoking. */ 38 struct rcu_head srcu_barrier_head; /* For srcu_barrier() use. */ 39 struct srcu_node *mynode; /* Leaf srcu_node. */ 40 unsigned long grpmask; /* Mask for leaf srcu_node */ 41 /* ->srcu_data_have_cbs[]. */ 42 int cpu; 43 struct srcu_struct *ssp; 44 }; 45 46 /* 47 * Node in SRCU combining tree, similar in function to rcu_data. 48 */ 49 struct srcu_node { 50 spinlock_t __private lock; 51 unsigned long srcu_have_cbs[4]; /* GP seq for children having CBs, but only */ 52 /* if greater than ->srcu_gp_seq. */ 53 unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs have CBs for given GP? */ 54 unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ 55 struct srcu_node *srcu_parent; /* Next up in tree. */ 56 int grplo; /* Least CPU for node. */ 57 int grphi; /* Biggest CPU for node. */ 58 }; 59 60 /* 61 * Per-SRCU-domain structure, update-side data linked from srcu_struct. 62 */ 63 struct srcu_usage { 64 struct srcu_node *node; /* Combining tree. */ 65 struct srcu_node *level[RCU_NUM_LVLS + 1]; 66 /* First node at each level. */ 67 int srcu_size_state; /* Small-to-big transition state. */ 68 struct mutex srcu_cb_mutex; /* Serialize CB preparation. */ 69 spinlock_t __private lock; /* Protect counters and size state. */ 70 struct mutex srcu_gp_mutex; /* Serialize GP work. */ 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 bool sda_is_static; /* May ->sda be passed to free_percpu()? */ 80 unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ 81 struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */ 82 struct completion srcu_barrier_completion; 83 /* Awaken barrier rq at end. */ 84 atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */ 85 /* callback for the barrier */ 86 /* operation. */ 87 unsigned long reschedule_jiffies; 88 unsigned long reschedule_count; 89 struct delayed_work work; 90 struct srcu_struct *srcu_ssp; 91 }; 92 93 /* 94 * Per-SRCU-domain structure, similar in function to rcu_state. 95 */ 96 struct srcu_struct { 97 unsigned int srcu_idx; /* Current rdr array element. */ 98 struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ 99 struct lockdep_map dep_map; 100 struct srcu_usage *srcu_sup; /* Update-side data. */ 101 }; 102 103 // Values for size state variable (->srcu_size_state). Once the state 104 // has been set to SRCU_SIZE_ALLOC, the grace-period code advances through 105 // this state machine one step per grace period until the SRCU_SIZE_BIG state 106 // is reached. Otherwise, the state machine remains in the SRCU_SIZE_SMALL 107 // state indefinitely. 108 #define SRCU_SIZE_SMALL 0 // No srcu_node combining tree, ->node == NULL 109 #define SRCU_SIZE_ALLOC 1 // An srcu_node tree is being allocated, initialized, 110 // and then referenced by ->node. It will not be used. 111 #define SRCU_SIZE_WAIT_BARRIER 2 // The srcu_node tree starts being used by everything 112 // except call_srcu(), especially by srcu_barrier(). 113 // By the end of this state, all CPUs and threads 114 // are aware of this tree's existence. 115 #define SRCU_SIZE_WAIT_CALL 3 // The srcu_node tree starts being used by call_srcu(). 116 // By the end of this state, all of the call_srcu() 117 // invocations that were running on a non-boot CPU 118 // and using the boot CPU's callback queue will have 119 // completed. 120 #define SRCU_SIZE_WAIT_CBS1 4 // Don't trust the ->srcu_have_cbs[] grace-period 121 #define SRCU_SIZE_WAIT_CBS2 5 // sequence elements or the ->srcu_data_have_cbs[] 122 #define SRCU_SIZE_WAIT_CBS3 6 // CPU-bitmask elements until all four elements of 123 #define SRCU_SIZE_WAIT_CBS4 7 // each array have been initialized. 124 #define SRCU_SIZE_BIG 8 // The srcu_node combining tree is fully initialized 125 // and all aspects of it are being put to use. 126 127 /* Values for state variable (bottom bits of ->srcu_gp_seq). */ 128 #define SRCU_STATE_IDLE 0 129 #define SRCU_STATE_SCAN1 1 130 #define SRCU_STATE_SCAN2 2 131 132 /* 133 * Values for initializing gp sequence fields. Higher values allow wrap arounds to 134 * occur earlier. 135 * The second value with state is useful in the case of static initialization of 136 * srcu_usage where srcu_gp_seq_needed is expected to have some state value in its 137 * lower bits (or else it will appear to be already initialized within 138 * the call check_init_srcu_struct()). 139 */ 140 #define SRCU_GP_SEQ_INITIAL_VAL ((0UL - 100UL) << RCU_SEQ_CTR_SHIFT) 141 #define SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE (SRCU_GP_SEQ_INITIAL_VAL - 1) 142 143 #define __SRCU_USAGE_INIT(name) \ 144 { \ 145 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 146 .srcu_gp_seq = SRCU_GP_SEQ_INITIAL_VAL, \ 147 .srcu_gp_seq_needed = SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE, \ 148 .srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL, \ 149 .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ 150 } 151 152 #define __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ 153 .srcu_sup = &usage_name, \ 154 __SRCU_DEP_MAP_INIT(name) 155 156 #define __SRCU_STRUCT_INIT_MODULE(name, usage_name) \ 157 { \ 158 __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ 159 } 160 161 #define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name) \ 162 { \ 163 .sda = &pcpu_name, \ 164 __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ 165 } 166 167 /* 168 * Define and initialize a srcu struct at build time. 169 * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it. 170 * 171 * Note that although DEFINE_STATIC_SRCU() hides the name from other 172 * files, the per-CPU variable rules nevertheless require that the 173 * chosen name be globally unique. These rules also prohibit use of 174 * DEFINE_STATIC_SRCU() within a function. If these rules are too 175 * restrictive, declare the srcu_struct manually. For example, in 176 * each file: 177 * 178 * static struct srcu_struct my_srcu; 179 * 180 * Then, before the first use of each my_srcu, manually initialize it: 181 * 182 * init_srcu_struct(&my_srcu); 183 * 184 * See include/linux/percpu-defs.h for the rules on per-CPU variables. 185 */ 186 #ifdef MODULE 187 # define __DEFINE_SRCU(name, is_static) \ 188 static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \ 189 is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage); \ 190 extern struct srcu_struct * const __srcu_struct_##name; \ 191 struct srcu_struct * const __srcu_struct_##name \ 192 __section("___srcu_struct_ptrs") = &name 193 #else 194 # define __DEFINE_SRCU(name, is_static) \ 195 static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \ 196 static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \ 197 is_static struct srcu_struct name = \ 198 __SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data) 199 #endif 200 #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) 201 #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) 202 203 void synchronize_srcu_expedited(struct srcu_struct *ssp); 204 void srcu_barrier(struct srcu_struct *ssp); 205 void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); 206 207 #endif 208