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 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
  74         while (list) {
  75                 struct llist_node *t = list;
  76                 list = llist_next(list);
  77
  78                 t->next = reverse;
  79                 reverse = t;
  80         }
  81
  82         /* Then do the wakeups */
  83
  84         while (reverse) {
  85                 cl = container_of(reverse, struct closure, list);
  86                 reverse = llist_next(reverse);
  87
  88                 closure_set_waiting(cl, 0);
  89                 closure_sub(cl, CLOSURE_WAITING + 1);
  90         }
  91 }
  92 EXPORT_SYMBOL(__closure_wake_up);
  93
  94 /**
  95  * closure_wait - add a closure to a waitlist
  96  *
  97  * @waitlist will own a ref on @cl, which will be released when
  98  * closure_wake_up() is called on @waitlist.
  99  *
 100  */
 101 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
 102 {
 103         if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
 104                 return false;
 105
 106         closure_set_waiting(cl, _RET_IP_);
 107         atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
 108         llist_add(&cl->list, &waitlist->list);
 109
 110         return true;
 111 }
 112 EXPORT_SYMBOL(closure_wait);
 113
 114 /**
 115  * closure_sync - sleep until a closure has nothing left to wait on
 116  *
 117  * Sleeps until the refcount hits 1 - the thread that's running the closure owns
 118  * the last refcount.
 119  */
 120 void closure_sync(struct closure *cl)
 121 {
 122         while (1) {
 123                 __closure_start_sleep(cl);
 124                 closure_set_ret_ip(cl);
 125
 126                 if ((atomic_read(&cl->remaining) &
 127                      CLOSURE_REMAINING_MASK) == 1)
 128                         break;
 129
 130                 schedule();
 131         }
 132
 133         __closure_end_sleep(cl);
 134 }
 135 EXPORT_SYMBOL(closure_sync);
 136
 137 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 138
 139 static LIST_HEAD(closure_list);
 140 static DEFINE_SPINLOCK(closure_list_lock);
 141
 142 void closure_debug_create(struct closure *cl)
 143 {
 144         unsigned long flags;
 145
 146         BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
 147         cl->magic = CLOSURE_MAGIC_ALIVE;
 148
 149         spin_lock_irqsave(&closure_list_lock, flags);
 150         list_add(&cl->all, &closure_list);
 151         spin_unlock_irqrestore(&closure_list_lock, flags);
 152 }
 153 EXPORT_SYMBOL(closure_debug_create);
 154
 155 void closure_debug_destroy(struct closure *cl)
 156 {
 157         unsigned long flags;
 158
 159         BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
 160         cl->magic = CLOSURE_MAGIC_DEAD;
 161
 162         spin_lock_irqsave(&closure_list_lock, flags);
 163         list_del(&cl->all);
 164         spin_unlock_irqrestore(&closure_list_lock, flags);
 165 }
 166 EXPORT_SYMBOL(closure_debug_destroy);
 167
 168 static struct dentry *debug;
 169
 170 static int debug_seq_show(struct seq_file *f, void *data)
 171 {
 172         struct closure *cl;
 173         spin_lock_irq(&closure_list_lock);
 174
 175         list_for_each_entry(cl, &closure_list, all) {
 176                 int r = atomic_read(&cl->remaining);
 177
 178                 seq_printf(f, "%p: %pF -> %pf p %p r %i ",
 179                            cl, (void *) cl->ip, cl->fn, cl->parent,
 180                            r & CLOSURE_REMAINING_MASK);
 181
 182                 seq_printf(f, "%s%s%s%s\n",
 183                            test_bit(WORK_STRUCT_PENDING_BIT,
 184                                     work_data_bits(&cl->work)) ? "Q" : "",
 185                            r & CLOSURE_RUNNING  ? "R" : "",
 186                            r & CLOSURE_STACK    ? "S" : "",
 187                            r & CLOSURE_SLEEPING ? "Sl" : "");
 188
 189                 if (r & CLOSURE_WAITING)
 190                         seq_printf(f, " W %pF\n",
 191                                    (void *) cl->waiting_on);
 192
 193                 seq_printf(f, "\n");
 194         }
 195
 196         spin_unlock_irq(&closure_list_lock);
 197         return 0;
 198 }
 199
 200 static int debug_seq_open(struct inode *inode, struct file *file)
 201 {
 202         return single_open(file, debug_seq_show, NULL);
 203 }
 204
 205 static const struct file_operations debug_ops = {
 206         .owner          = THIS_MODULE,
 207         .open           = debug_seq_open,
 208         .read           = seq_read,
 209         .release        = single_release
 210 };
 211
 212 void __init closure_debug_init(void)
 213 {
 214         debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
 215 }
 216
 217 #endif
 218
 219 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
 220 MODULE_LICENSE("GPL");