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); 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 void closure_sync_fn(struct closure *cl) 112 { 113 struct closure_syncer *s = cl->s; 114 struct task_struct *p; 115 116 rcu_read_lock(); 117 p = READ_ONCE(s->task); 118 s->done = 1; 119 wake_up_process(p); 120 rcu_read_unlock(); 121 } 122 123 void __sched __closure_sync(struct closure *cl) 124 { 125 struct closure_syncer s = { .task = current }; 126 127 cl->s = &s; 128 continue_at(cl, closure_sync_fn, NULL); 129 130 while (1) { 131 set_current_state(TASK_UNINTERRUPTIBLE); 132 if (s.done) 133 break; 134 schedule(); 135 } 136 137 __set_current_state(TASK_RUNNING); 138 } 139 EXPORT_SYMBOL(__closure_sync); 140 141 #ifdef CONFIG_DEBUG_CLOSURES 142 143 static LIST_HEAD(closure_list); 144 static DEFINE_SPINLOCK(closure_list_lock); 145 146 void closure_debug_create(struct closure *cl) 147 { 148 unsigned long flags; 149 150 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE); 151 cl->magic = CLOSURE_MAGIC_ALIVE; 152 153 spin_lock_irqsave(&closure_list_lock, flags); 154 list_add(&cl->all, &closure_list); 155 spin_unlock_irqrestore(&closure_list_lock, flags); 156 } 157 EXPORT_SYMBOL(closure_debug_create); 158 159 void closure_debug_destroy(struct closure *cl) 160 { 161 unsigned long flags; 162 163 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE); 164 cl->magic = CLOSURE_MAGIC_DEAD; 165 166 spin_lock_irqsave(&closure_list_lock, flags); 167 list_del(&cl->all); 168 spin_unlock_irqrestore(&closure_list_lock, flags); 169 } 170 EXPORT_SYMBOL(closure_debug_destroy); 171 172 static int debug_show(struct seq_file *f, void *data) 173 { 174 struct closure *cl; 175 176 spin_lock_irq(&closure_list_lock); 177 178 list_for_each_entry(cl, &closure_list, all) { 179 int r = atomic_read(&cl->remaining); 180 181 seq_printf(f, "%p: %pS -> %pS p %p r %i ", 182 cl, (void *) cl->ip, cl->fn, cl->parent, 183 r & CLOSURE_REMAINING_MASK); 184 185 seq_printf(f, "%s%s\n", 186 test_bit(WORK_STRUCT_PENDING_BIT, 187 work_data_bits(&cl->work)) ? "Q" : "", 188 r & CLOSURE_RUNNING ? "R" : ""); 189 190 if (r & CLOSURE_WAITING) 191 seq_printf(f, " W %pS\n", 192 (void *) cl->waiting_on); 193 194 seq_puts(f, "\n"); 195 } 196 197 spin_unlock_irq(&closure_list_lock); 198 return 0; 199 } 200 201 DEFINE_SHOW_ATTRIBUTE(debug); 202 203 static int __init closure_debug_init(void) 204 { 205 debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops); 206 return 0; 207 } 208 late_initcall(closure_debug_init) 209 210 #endif 211