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