1 /* 2 * Asynchronous refcounty things 3 * 4 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com> 5 * Copyright 2012 Google, Inc. 6 */ 7 8 #include <linux/debugfs.h> 9 #include <linux/module.h> 10 #include <linux/seq_file.h> 11 12 #include "closure.h" 13 14 static inline void closure_put_after_sub(struct closure *cl, int flags) 15 { 16 int r = flags & CLOSURE_REMAINING_MASK; 17 18 BUG_ON(flags & CLOSURE_GUARD_MASK); 19 BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR)); 20 21 /* Must deliver precisely one wakeup */ 22 if (r == 1 && (flags & CLOSURE_SLEEPING)) 23 wake_up_process(cl->task); 24 25 if (!r) { 26 if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) { 27 atomic_set(&cl->remaining, 28 CLOSURE_REMAINING_INITIALIZER); 29 closure_queue(cl); 30 } else { 31 struct closure *parent = cl->parent; 32 closure_fn *destructor = cl->fn; 33 34 closure_debug_destroy(cl); 35 36 if (destructor) 37 destructor(cl); 38 39 if (parent) 40 closure_put(parent); 41 } 42 } 43 } 44 45 /* For clearing flags with the same atomic op as a put */ 46 void closure_sub(struct closure *cl, int v) 47 { 48 closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining)); 49 } 50 EXPORT_SYMBOL(closure_sub); 51 52 /** 53 * closure_put - decrement a closure's refcount 54 */ 55 void closure_put(struct closure *cl) 56 { 57 closure_put_after_sub(cl, atomic_dec_return(&cl->remaining)); 58 } 59 EXPORT_SYMBOL(closure_put); 60 61 /** 62 * closure_wake_up - wake up all closures on a wait list, without memory barrier 63 */ 64 void __closure_wake_up(struct closure_waitlist *wait_list) 65 { 66 struct llist_node *list; 67 struct closure *cl; 68 struct llist_node *reverse = NULL; 69 70 list = llist_del_all(&wait_list->list); 71 72 /* We first reverse the list to preserve FIFO ordering and fairness */ 73 reverse = llist_reverse_order(list); 74 75 /* Then do the wakeups */ 76 llist_for_each_entry(cl, reverse, list) { 77 closure_set_waiting(cl, 0); 78 closure_sub(cl, CLOSURE_WAITING + 1); 79 } 80 } 81 EXPORT_SYMBOL(__closure_wake_up); 82 83 /** 84 * closure_wait - add a closure to a waitlist 85 * 86 * @waitlist will own a ref on @cl, which will be released when 87 * closure_wake_up() is called on @waitlist. 88 * 89 */ 90 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl) 91 { 92 if (atomic_read(&cl->remaining) & CLOSURE_WAITING) 93 return false; 94 95 closure_set_waiting(cl, _RET_IP_); 96 atomic_add(CLOSURE_WAITING + 1, &cl->remaining); 97 llist_add(&cl->list, &waitlist->list); 98 99 return true; 100 } 101 EXPORT_SYMBOL(closure_wait); 102 103 /** 104 * closure_sync - sleep until a closure has nothing left to wait on 105 * 106 * Sleeps until the refcount hits 1 - the thread that's running the closure owns 107 * the last refcount. 108 */ 109 void closure_sync(struct closure *cl) 110 { 111 while (1) { 112 __closure_start_sleep(cl); 113 closure_set_ret_ip(cl); 114 115 if ((atomic_read(&cl->remaining) & 116 CLOSURE_REMAINING_MASK) == 1) 117 break; 118 119 schedule(); 120 } 121 122 __closure_end_sleep(cl); 123 } 124 EXPORT_SYMBOL(closure_sync); 125 126 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG 127 128 static LIST_HEAD(closure_list); 129 static DEFINE_SPINLOCK(closure_list_lock); 130 131 void closure_debug_create(struct closure *cl) 132 { 133 unsigned long flags; 134 135 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE); 136 cl->magic = CLOSURE_MAGIC_ALIVE; 137 138 spin_lock_irqsave(&closure_list_lock, flags); 139 list_add(&cl->all, &closure_list); 140 spin_unlock_irqrestore(&closure_list_lock, flags); 141 } 142 EXPORT_SYMBOL(closure_debug_create); 143 144 void closure_debug_destroy(struct closure *cl) 145 { 146 unsigned long flags; 147 148 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE); 149 cl->magic = CLOSURE_MAGIC_DEAD; 150 151 spin_lock_irqsave(&closure_list_lock, flags); 152 list_del(&cl->all); 153 spin_unlock_irqrestore(&closure_list_lock, flags); 154 } 155 EXPORT_SYMBOL(closure_debug_destroy); 156 157 static struct dentry *debug; 158 159 static int debug_seq_show(struct seq_file *f, void *data) 160 { 161 struct closure *cl; 162 spin_lock_irq(&closure_list_lock); 163 164 list_for_each_entry(cl, &closure_list, all) { 165 int r = atomic_read(&cl->remaining); 166 167 seq_printf(f, "%p: %pF -> %pf p %p r %i ", 168 cl, (void *) cl->ip, cl->fn, cl->parent, 169 r & CLOSURE_REMAINING_MASK); 170 171 seq_printf(f, "%s%s%s%s\n", 172 test_bit(WORK_STRUCT_PENDING_BIT, 173 work_data_bits(&cl->work)) ? "Q" : "", 174 r & CLOSURE_RUNNING ? "R" : "", 175 r & CLOSURE_STACK ? "S" : "", 176 r & CLOSURE_SLEEPING ? "Sl" : ""); 177 178 if (r & CLOSURE_WAITING) 179 seq_printf(f, " W %pF\n", 180 (void *) cl->waiting_on); 181 182 seq_printf(f, "\n"); 183 } 184 185 spin_unlock_irq(&closure_list_lock); 186 return 0; 187 } 188 189 static int debug_seq_open(struct inode *inode, struct file *file) 190 { 191 return single_open(file, debug_seq_show, NULL); 192 } 193 194 static const struct file_operations debug_ops = { 195 .owner = THIS_MODULE, 196 .open = debug_seq_open, 197 .read = seq_read, 198 .release = single_release 199 }; 200 201 void __init closure_debug_init(void) 202 { 203 debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops); 204 } 205 206 #endif 207 208 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>"); 209 MODULE_LICENSE("GPL"); 210