drivers/md/bcache/closure.c

   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 void closure_queue(struct closure *cl)
  15 {
  16         struct workqueue_struct *wq = cl->wq;
  17         if (wq) {
  18                 INIT_WORK(&cl->work, cl->work.func);
  19                 BUG_ON(!queue_work(wq, &cl->work));
  20         } else
  21                 cl->fn(cl);
  22 }
  23 EXPORT_SYMBOL_GPL(closure_queue);
  24
  25 #define CL_FIELD(type, field)                                   \
  26         case TYPE_ ## type:                                     \
  27         return &container_of(cl, struct type, cl)->field
  28
  29 static struct closure_waitlist *closure_waitlist(struct closure *cl)
  30 {
  31         switch (cl->type) {
  32                 CL_FIELD(closure_with_waitlist, wait);
  33                 CL_FIELD(closure_with_waitlist_and_timer, wait);
  34         default:
  35                 return NULL;
  36         }
  37 }
  38
  39 static struct timer_list *closure_timer(struct closure *cl)
  40 {
  41         switch (cl->type) {
  42                 CL_FIELD(closure_with_timer, timer);
  43                 CL_FIELD(closure_with_waitlist_and_timer, timer);
  44         default:
  45                 return NULL;
  46         }
  47 }
  48
  49 static inline void closure_put_after_sub(struct closure *cl, int flags)
  50 {
  51         int r = flags & CLOSURE_REMAINING_MASK;
  52
  53         BUG_ON(flags & CLOSURE_GUARD_MASK);
  54         BUG_ON(!r && (flags & ~(CLOSURE_DESTRUCTOR|CLOSURE_BLOCKING)));
  55
  56         /* Must deliver precisely one wakeup */
  57         if (r == 1 && (flags & CLOSURE_SLEEPING))
  58                 wake_up_process(cl->task);
  59
  60         if (!r) {
  61                 if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
  62                         /* CLOSURE_BLOCKING might be set - clear it */
  63                         atomic_set(&cl->remaining,
  64                                    CLOSURE_REMAINING_INITIALIZER);
  65                         closure_queue(cl);
  66                 } else {
  67                         struct closure *parent = cl->parent;
  68                         struct closure_waitlist *wait = closure_waitlist(cl);
  69
  70                         closure_debug_destroy(cl);
  71
  72                         atomic_set(&cl->remaining, -1);
  73
  74                         if (wait)
  75                                 closure_wake_up(wait);
  76
  77                         if (cl->fn)
  78                                 cl->fn(cl);
  79
  80                         if (parent)
  81                                 closure_put(parent);
  82                 }
  83         }
  84 }
  85
  86 /* For clearing flags with the same atomic op as a put */
  87 void closure_sub(struct closure *cl, int v)
  88 {
  89         closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
  90 }
  91 EXPORT_SYMBOL_GPL(closure_sub);
  92
  93 void closure_put(struct closure *cl)
  94 {
  95         closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
  96 }
  97 EXPORT_SYMBOL_GPL(closure_put);
  98
  99 static void set_waiting(struct closure *cl, unsigned long f)
 100 {
 101 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 102         cl->waiting_on = f;
 103 #endif
 104 }
 105
 106 void __closure_wake_up(struct closure_waitlist *wait_list)
 107 {
 108         struct llist_node *list;
 109         struct closure *cl;
 110         struct llist_node *reverse = NULL;
 111
 112         list = llist_del_all(&wait_list->list);
 113
 114         /* We first reverse the list to preserve FIFO ordering and fairness */
 115
 116         while (list) {
 117                 struct llist_node *t = list;
 118                 list = llist_next(list);
 119
 120                 t->next = reverse;
 121                 reverse = t;
 122         }
 123
 124         /* Then do the wakeups */
 125
 126         while (reverse) {
 127                 cl = container_of(reverse, struct closure, list);
 128                 reverse = llist_next(reverse);
 129
 130                 set_waiting(cl, 0);
 131                 closure_sub(cl, CLOSURE_WAITING + 1);
 132         }
 133 }
 134 EXPORT_SYMBOL_GPL(__closure_wake_up);
 135
 136 bool closure_wait(struct closure_waitlist *list, struct closure *cl)
 137 {
 138         if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
 139                 return false;
 140
 141         set_waiting(cl, _RET_IP_);
 142         atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
 143         llist_add(&cl->list, &list->list);
 144
 145         return true;
 146 }
 147 EXPORT_SYMBOL_GPL(closure_wait);
 148
 149 /**
 150  * closure_sync() - sleep until a closure a closure has nothing left to wait on
 151  *
 152  * Sleeps until the refcount hits 1 - the thread that's running the closure owns
 153  * the last refcount.
 154  */
 155 void closure_sync(struct closure *cl)
 156 {
 157         while (1) {
 158                 __closure_start_sleep(cl);
 159                 closure_set_ret_ip(cl);
 160
 161                 if ((atomic_read(&cl->remaining) &
 162                      CLOSURE_REMAINING_MASK) == 1)
 163                         break;
 164
 165                 schedule();
 166         }
 167
 168         __closure_end_sleep(cl);
 169 }
 170 EXPORT_SYMBOL_GPL(closure_sync);
 171
 172 /**
 173  * closure_trylock() - try to acquire the closure, without waiting
 174  * @cl:         closure to lock
 175  *
 176  * Returns true if the closure was succesfully locked.
 177  */
 178 bool closure_trylock(struct closure *cl, struct closure *parent)
 179 {
 180         if (atomic_cmpxchg(&cl->remaining, -1,
 181                            CLOSURE_REMAINING_INITIALIZER) != -1)
 182                 return false;
 183
 184         closure_set_ret_ip(cl);
 185
 186         smp_mb();
 187         cl->parent = parent;
 188         if (parent)
 189                 closure_get(parent);
 190
 191         closure_debug_create(cl);
 192         return true;
 193 }
 194 EXPORT_SYMBOL_GPL(closure_trylock);
 195
 196 void __closure_lock(struct closure *cl, struct closure *parent,
 197                     struct closure_waitlist *wait_list)
 198 {
 199         struct closure wait;
 200         closure_init_stack(&wait);
 201
 202         while (1) {
 203                 if (closure_trylock(cl, parent))
 204                         return;
 205
 206                 closure_wait_event_sync(wait_list, &wait,
 207                                         atomic_read(&cl->remaining) == -1);
 208         }
 209 }
 210 EXPORT_SYMBOL_GPL(__closure_lock);
 211
 212 static void closure_delay_timer_fn(unsigned long data)
 213 {
 214         struct closure *cl = (struct closure *) data;
 215         closure_sub(cl, CLOSURE_TIMER + 1);
 216 }
 217
 218 void do_closure_timer_init(struct closure *cl)
 219 {
 220         struct timer_list *timer = closure_timer(cl);
 221
 222         init_timer(timer);
 223         timer->data     = (unsigned long) cl;
 224         timer->function = closure_delay_timer_fn;
 225 }
 226 EXPORT_SYMBOL_GPL(do_closure_timer_init);
 227
 228 bool __closure_delay(struct closure *cl, unsigned long delay,
 229                      struct timer_list *timer)
 230 {
 231         if (atomic_read(&cl->remaining) & CLOSURE_TIMER)
 232                 return false;
 233
 234         BUG_ON(timer_pending(timer));
 235
 236         timer->expires  = jiffies + delay;
 237
 238         atomic_add(CLOSURE_TIMER + 1, &cl->remaining);
 239         add_timer(timer);
 240         return true;
 241 }
 242 EXPORT_SYMBOL_GPL(__closure_delay);
 243
 244 void __closure_flush(struct closure *cl, struct timer_list *timer)
 245 {
 246         if (del_timer(timer))
 247                 closure_sub(cl, CLOSURE_TIMER + 1);
 248 }
 249 EXPORT_SYMBOL_GPL(__closure_flush);
 250
 251 void __closure_flush_sync(struct closure *cl, struct timer_list *timer)
 252 {
 253         if (del_timer_sync(timer))
 254                 closure_sub(cl, CLOSURE_TIMER + 1);
 255 }
 256 EXPORT_SYMBOL_GPL(__closure_flush_sync);
 257
 258 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 259
 260 static LIST_HEAD(closure_list);
 261 static DEFINE_SPINLOCK(closure_list_lock);
 262
 263 void closure_debug_create(struct closure *cl)
 264 {
 265         unsigned long flags;
 266
 267         BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
 268         cl->magic = CLOSURE_MAGIC_ALIVE;
 269
 270         spin_lock_irqsave(&closure_list_lock, flags);
 271         list_add(&cl->all, &closure_list);
 272         spin_unlock_irqrestore(&closure_list_lock, flags);
 273 }
 274 EXPORT_SYMBOL_GPL(closure_debug_create);
 275
 276 void closure_debug_destroy(struct closure *cl)
 277 {
 278         unsigned long flags;
 279
 280         BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
 281         cl->magic = CLOSURE_MAGIC_DEAD;
 282
 283         spin_lock_irqsave(&closure_list_lock, flags);
 284         list_del(&cl->all);
 285         spin_unlock_irqrestore(&closure_list_lock, flags);
 286 }
 287 EXPORT_SYMBOL_GPL(closure_debug_destroy);
 288
 289 static struct dentry *debug;
 290
 291 #define work_data_bits(work) ((unsigned long *)(&(work)->data))
 292
 293 static int debug_seq_show(struct seq_file *f, void *data)
 294 {
 295         struct closure *cl;
 296         spin_lock_irq(&closure_list_lock);
 297
 298         list_for_each_entry(cl, &closure_list, all) {
 299                 int r = atomic_read(&cl->remaining);
 300
 301                 seq_printf(f, "%p: %pF -> %pf p %p r %i ",
 302                            cl, (void *) cl->ip, cl->fn, cl->parent,
 303                            r & CLOSURE_REMAINING_MASK);
 304
 305                 seq_printf(f, "%s%s%s%s%s%s\n",
 306                            test_bit(WORK_STRUCT_PENDING,
 307                                     work_data_bits(&cl->work)) ? "Q" : "",
 308                            r & CLOSURE_RUNNING  ? "R" : "",
 309                            r & CLOSURE_BLOCKING ? "B" : "",
 310                            r & CLOSURE_STACK    ? "S" : "",
 311                            r & CLOSURE_SLEEPING ? "Sl" : "",
 312                            r & CLOSURE_TIMER    ? "T" : "");
 313
 314                 if (r & CLOSURE_WAITING)
 315                         seq_printf(f, " W %pF\n",
 316                                    (void *) cl->waiting_on);
 317
 318                 seq_printf(f, "\n");
 319         }
 320
 321         spin_unlock_irq(&closure_list_lock);
 322         return 0;
 323 }
 324
 325 static int debug_seq_open(struct inode *inode, struct file *file)
 326 {
 327         return single_open(file, debug_seq_show, NULL);
 328 }
 329
 330 static const struct file_operations debug_ops = {
 331         .owner          = THIS_MODULE,
 332         .open           = debug_seq_open,
 333         .read           = seq_read,
 334         .release        = single_release
 335 };
 336
 337 void __init closure_debug_init(void)
 338 {
 339         debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
 340 }
 341
 342 #endif
 343
 344 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
 345 MODULE_LICENSE("GPL");