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/debugfs.h> 10 #include <linux/module.h> 11 #include <linux/seq_file.h> 12 #include <linux/sched/debug.h> 13 14 #include "closure.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 49 /* 50 * closure_put - decrement a closure's refcount 51 */ 52 void closure_put(struct closure *cl) 53 { 54 closure_put_after_sub(cl, atomic_dec_return(&cl->remaining)); 55 } 56 57 /* 58 * closure_wake_up - wake up all closures on a wait list, without memory barrier 59 */ 60 void __closure_wake_up(struct closure_waitlist *wait_list) 61 { 62 struct llist_node *list; 63 struct closure *cl, *t; 64 struct llist_node *reverse = NULL; 65 66 list = llist_del_all(&wait_list->list); 67 68 /* We first reverse the list to preserve FIFO ordering and fairness */ 69 reverse = llist_reverse_order(list); 70 71 /* Then do the wakeups */ 72 llist_for_each_entry_safe(cl, t, reverse, list) { 73 closure_set_waiting(cl, 0); 74 closure_sub(cl, CLOSURE_WAITING + 1); 75 } 76 } 77 78 /** 79 * closure_wait - add a closure to a waitlist 80 * @waitlist: will own a ref on @cl, which will be released when 81 * closure_wake_up() is called on @waitlist. 82 * @cl: closure pointer. 83 * 84 */ 85 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl) 86 { 87 if (atomic_read(&cl->remaining) & CLOSURE_WAITING) 88 return false; 89 90 closure_set_waiting(cl, _RET_IP_); 91 atomic_add(CLOSURE_WAITING + 1, &cl->remaining); 92 llist_add(&cl->list, &waitlist->list); 93 94 return true; 95 } 96 97 struct closure_syncer { 98 struct task_struct *task; 99 int done; 100 }; 101 102 static void closure_sync_fn(struct closure *cl) 103 { 104 struct closure_syncer *s = cl->s; 105 struct task_struct *p; 106 107 rcu_read_lock(); 108 p = READ_ONCE(s->task); 109 s->done = 1; 110 wake_up_process(p); 111 rcu_read_unlock(); 112 } 113 114 void __sched __closure_sync(struct closure *cl) 115 { 116 struct closure_syncer s = { .task = current }; 117 118 cl->s = &s; 119 continue_at(cl, closure_sync_fn, NULL); 120 121 while (1) { 122 set_current_state(TASK_UNINTERRUPTIBLE); 123 if (s.done) 124 break; 125 schedule(); 126 } 127 128 __set_current_state(TASK_RUNNING); 129 } 130 131 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG 132 133 static LIST_HEAD(closure_list); 134 static DEFINE_SPINLOCK(closure_list_lock); 135 136 void closure_debug_create(struct closure *cl) 137 { 138 unsigned long flags; 139 140 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE); 141 cl->magic = CLOSURE_MAGIC_ALIVE; 142 143 spin_lock_irqsave(&closure_list_lock, flags); 144 list_add(&cl->all, &closure_list); 145 spin_unlock_irqrestore(&closure_list_lock, flags); 146 } 147 148 void closure_debug_destroy(struct closure *cl) 149 { 150 unsigned long flags; 151 152 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE); 153 cl->magic = CLOSURE_MAGIC_DEAD; 154 155 spin_lock_irqsave(&closure_list_lock, flags); 156 list_del(&cl->all); 157 spin_unlock_irqrestore(&closure_list_lock, flags); 158 } 159 160 static struct dentry *closure_debug; 161 162 static int debug_show(struct seq_file *f, void *data) 163 { 164 struct closure *cl; 165 166 spin_lock_irq(&closure_list_lock); 167 168 list_for_each_entry(cl, &closure_list, all) { 169 int r = atomic_read(&cl->remaining); 170 171 seq_printf(f, "%p: %pS -> %pS p %p r %i ", 172 cl, (void *) cl->ip, cl->fn, cl->parent, 173 r & CLOSURE_REMAINING_MASK); 174 175 seq_printf(f, "%s%s\n", 176 test_bit(WORK_STRUCT_PENDING_BIT, 177 work_data_bits(&cl->work)) ? "Q" : "", 178 r & CLOSURE_RUNNING ? "R" : ""); 179 180 if (r & CLOSURE_WAITING) 181 seq_printf(f, " W %pS\n", 182 (void *) cl->waiting_on); 183 184 seq_printf(f, "\n"); 185 } 186 187 spin_unlock_irq(&closure_list_lock); 188 return 0; 189 } 190 191 DEFINE_SHOW_ATTRIBUTE(debug); 192 193 void __init closure_debug_init(void) 194 { 195 if (!IS_ERR_OR_NULL(bcache_debug)) 196 /* 197 * it is unnecessary to check return value of 198 * debugfs_create_file(), we should not care 199 * about this. 200 */ 201 closure_debug = debugfs_create_file( 202 "closures", 0400, bcache_debug, NULL, &debug_fops); 203 } 204 #endif 205 206 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>"); 207 MODULE_LICENSE("GPL"); 208