1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Asynchronous refcounty things 4 * 5 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com> 6 * Copyright 2012 Google, Inc. 7 */ 8 9 #include <linux/closure.h> 10 #include <linux/debugfs.h> 11 #include <linux/export.h> 12 #include <linux/rcupdate.h> 13 #include <linux/seq_file.h> 14 #include <linux/sched/debug.h> 15 16 static inline void closure_put_after_sub(struct closure *cl, int flags) 17 { 18 int r = flags & CLOSURE_REMAINING_MASK; 19 20 BUG_ON(flags & CLOSURE_GUARD_MASK); 21 BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR)); 22 23 if (!r) { 24 smp_acquire__after_ctrl_dep(); 25 26 cl->closure_get_happened = false; 27 28 if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) { 29 atomic_set(&cl->remaining, 30 CLOSURE_REMAINING_INITIALIZER); 31 closure_queue(cl); 32 } else { 33 struct closure *parent = cl->parent; 34 closure_fn *destructor = cl->fn; 35 36 closure_debug_destroy(cl); 37 38 if (destructor) 39 destructor(&cl->work); 40 41 if (parent) 42 closure_put(parent); 43 } 44 } 45 } 46 47 /* For clearing flags with the same atomic op as a put */ 48 void closure_sub(struct closure *cl, int v) 49 { 50 closure_put_after_sub(cl, atomic_sub_return_release(v, &cl->remaining)); 51 } 52 EXPORT_SYMBOL(closure_sub); 53 54 /* 55 * closure_put - decrement a closure's refcount 56 */ 57 void closure_put(struct closure *cl) 58 { 59 closure_put_after_sub(cl, atomic_dec_return_release(&cl->remaining)); 60 } 61 EXPORT_SYMBOL(closure_put); 62 63 /* 64 * closure_wake_up - wake up all closures on a wait list, without memory barrier 65 */ 66 void __closure_wake_up(struct closure_waitlist *wait_list) 67 { 68 struct llist_node *list; 69 struct closure *cl, *t; 70 struct llist_node *reverse = NULL; 71 72 list = llist_del_all(&wait_list->list); 73 74 /* We first reverse the list to preserve FIFO ordering and fairness */ 75 reverse = llist_reverse_order(list); 76 77 /* Then do the wakeups */ 78 llist_for_each_entry_safe(cl, t, reverse, list) { 79 closure_set_waiting(cl, 0); 80 closure_sub(cl, CLOSURE_WAITING + 1); 81 } 82 } 83 EXPORT_SYMBOL(__closure_wake_up); 84 85 /** 86 * closure_wait - add a closure to a waitlist 87 * @waitlist: will own a ref on @cl, which will be released when 88 * closure_wake_up() is called on @waitlist. 89 * @cl: closure pointer. 90 * 91 */ 92 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl) 93 { 94 if (atomic_read(&cl->remaining) & CLOSURE_WAITING) 95 return false; 96 97 cl->closure_get_happened = true; 98 closure_set_waiting(cl, _RET_IP_); 99 atomic_add(CLOSURE_WAITING + 1, &cl->remaining); 100 llist_add(&cl->list, &waitlist->list); 101 102 return true; 103 } 104 EXPORT_SYMBOL(closure_wait); 105 106 struct closure_syncer { 107 struct task_struct *task; 108 int done; 109 }; 110 111 static CLOSURE_CALLBACK(closure_sync_fn) 112 { 113 struct closure *cl = container_of(ws, struct closure, work); 114 struct closure_syncer *s = cl->s; 115 struct task_struct *p; 116 117 rcu_read_lock(); 118 p = READ_ONCE(s->task); 119 s->done = 1; 120 wake_up_process(p); 121 rcu_read_unlock(); 122 } 123 124 void __sched __closure_sync(struct closure *cl) 125 { 126 struct closure_syncer s = { .task = current }; 127 128 cl->s = &s; 129 continue_at(cl, closure_sync_fn, NULL); 130 131 while (1) { 132 set_current_state(TASK_UNINTERRUPTIBLE); 133 if (s.done) 134 break; 135 schedule(); 136 } 137 138 __set_current_state(TASK_RUNNING); 139 } 140 EXPORT_SYMBOL(__closure_sync); 141 142 #ifdef CONFIG_DEBUG_CLOSURES 143 144 static LIST_HEAD(closure_list); 145 static DEFINE_SPINLOCK(closure_list_lock); 146 147 void closure_debug_create(struct closure *cl) 148 { 149 unsigned long flags; 150 151 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE); 152 cl->magic = CLOSURE_MAGIC_ALIVE; 153 154 spin_lock_irqsave(&closure_list_lock, flags); 155 list_add(&cl->all, &closure_list); 156 spin_unlock_irqrestore(&closure_list_lock, flags); 157 } 158 EXPORT_SYMBOL(closure_debug_create); 159 160 void closure_debug_destroy(struct closure *cl) 161 { 162 unsigned long flags; 163 164 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE); 165 cl->magic = CLOSURE_MAGIC_DEAD; 166 167 spin_lock_irqsave(&closure_list_lock, flags); 168 list_del(&cl->all); 169 spin_unlock_irqrestore(&closure_list_lock, flags); 170 } 171 EXPORT_SYMBOL(closure_debug_destroy); 172 173 static int debug_show(struct seq_file *f, void *data) 174 { 175 struct closure *cl; 176 177 spin_lock_irq(&closure_list_lock); 178 179 list_for_each_entry(cl, &closure_list, all) { 180 int r = atomic_read(&cl->remaining); 181 182 seq_printf(f, "%p: %pS -> %pS p %p r %i ", 183 cl, (void *) cl->ip, cl->fn, cl->parent, 184 r & CLOSURE_REMAINING_MASK); 185 186 seq_printf(f, "%s%s\n", 187 test_bit(WORK_STRUCT_PENDING_BIT, 188 work_data_bits(&cl->work)) ? "Q" : "", 189 r & CLOSURE_RUNNING ? "R" : ""); 190 191 if (r & CLOSURE_WAITING) 192 seq_printf(f, " W %pS\n", 193 (void *) cl->waiting_on); 194 195 seq_puts(f, "\n"); 196 } 197 198 spin_unlock_irq(&closure_list_lock); 199 return 0; 200 } 201 202 DEFINE_SHOW_ATTRIBUTE(debug); 203 204 static int __init closure_debug_init(void) 205 { 206 debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops); 207 return 0; 208 } 209 late_initcall(closure_debug_init) 210 211 #endif 212