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