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