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         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");