drivers/md/bcache/closure.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Asynchronous refcounty things
   4  *
   5  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
   6  * Copyright 2012 Google, Inc.
   7  */
   8
   9 #include <linux/debugfs.h>
  10 #include <linux/module.h>
  11 #include <linux/seq_file.h>
  12 #include <linux/sched/debug.h>
  13
  14 #include "closure.h"
  15
  16 static inline void closure_put_after_sub(struct closure *cl, int flags)
  17 {
  18         int r = flags & CLOSURE_REMAINING_MASK;
  19
  20         BUG_ON(flags & CLOSURE_GUARD_MASK);
  21         BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
  22
  23         if (!r) {
  24                 if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
  25                         atomic_set(&cl->remaining,
  26                                    CLOSURE_REMAINING_INITIALIZER);
  27                         closure_queue(cl);
  28                 } else {
  29                         struct closure *parent = cl->parent;
  30                         closure_fn *destructor = cl->fn;
  31
  32                         closure_debug_destroy(cl);
  33
  34                         if (destructor)
  35                                 destructor(cl);
  36
  37                         if (parent)
  38                                 closure_put(parent);
  39                 }
  40         }
  41 }
  42
  43 /* For clearing flags with the same atomic op as a put */
  44 void closure_sub(struct closure *cl, int v)
  45 {
  46         closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
  47 }
  48
  49 /*
  50  * closure_put - decrement a closure's refcount
  51  */
  52 void closure_put(struct closure *cl)
  53 {
  54         closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
  55 }
  56
  57 /*
  58  * closure_wake_up - wake up all closures on a wait list, without memory barrier
  59  */
  60 void __closure_wake_up(struct closure_waitlist *wait_list)
  61 {
  62         struct llist_node *list;
  63         struct closure *cl, *t;
  64         struct llist_node *reverse = NULL;
  65
  66         list = llist_del_all(&wait_list->list);
  67
  68         /* We first reverse the list to preserve FIFO ordering and fairness */
  69         reverse = llist_reverse_order(list);
  70
  71         /* Then do the wakeups */
  72         llist_for_each_entry_safe(cl, t, reverse, list) {
  73                 closure_set_waiting(cl, 0);
  74                 closure_sub(cl, CLOSURE_WAITING + 1);
  75         }
  76 }
  77
  78 /**
  79  * closure_wait - add a closure to a waitlist
  80  * @waitlist: will own a ref on @cl, which will be released when
  81  * closure_wake_up() is called on @waitlist.
  82  * @cl: closure pointer.
  83  *
  84  */
  85 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
  86 {
  87         if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
  88                 return false;
  89
  90         closure_set_waiting(cl, _RET_IP_);
  91         atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
  92         llist_add(&cl->list, &waitlist->list);
  93
  94         return true;
  95 }
  96
  97 struct closure_syncer {
  98         struct task_struct      *task;
  99         int                     done;
 100 };
 101
 102 static void closure_sync_fn(struct closure *cl)
 103 {
 104         struct closure_syncer *s = cl->s;
 105         struct task_struct *p;
 106
 107         rcu_read_lock();
 108         p = READ_ONCE(s->task);
 109         s->done = 1;
 110         wake_up_process(p);
 111         rcu_read_unlock();
 112 }
 113
 114 void __sched __closure_sync(struct closure *cl)
 115 {
 116         struct closure_syncer s = { .task = current };
 117
 118         cl->s = &s;
 119         continue_at(cl, closure_sync_fn, NULL);
 120
 121         while (1) {
 122                 set_current_state(TASK_UNINTERRUPTIBLE);
 123                 if (s.done)
 124                         break;
 125                 schedule();
 126         }
 127
 128         __set_current_state(TASK_RUNNING);
 129 }
 130
 131 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 132
 133 static LIST_HEAD(closure_list);
 134 static DEFINE_SPINLOCK(closure_list_lock);
 135
 136 void closure_debug_create(struct closure *cl)
 137 {
 138         unsigned long flags;
 139
 140         BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
 141         cl->magic = CLOSURE_MAGIC_ALIVE;
 142
 143         spin_lock_irqsave(&closure_list_lock, flags);
 144         list_add(&cl->all, &closure_list);
 145         spin_unlock_irqrestore(&closure_list_lock, flags);
 146 }
 147
 148 void closure_debug_destroy(struct closure *cl)
 149 {
 150         unsigned long flags;
 151
 152         BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
 153         cl->magic = CLOSURE_MAGIC_DEAD;
 154
 155         spin_lock_irqsave(&closure_list_lock, flags);
 156         list_del(&cl->all);
 157         spin_unlock_irqrestore(&closure_list_lock, flags);
 158 }
 159
 160 static struct dentry *closure_debug;
 161
 162 static int debug_show(struct seq_file *f, void *data)
 163 {
 164         struct closure *cl;
 165
 166         spin_lock_irq(&closure_list_lock);
 167
 168         list_for_each_entry(cl, &closure_list, all) {
 169                 int r = atomic_read(&cl->remaining);
 170
 171                 seq_printf(f, "%p: %pS -> %pS p %p r %i ",
 172                            cl, (void *) cl->ip, cl->fn, cl->parent,
 173                            r & CLOSURE_REMAINING_MASK);
 174
 175                 seq_printf(f, "%s%s\n",
 176                            test_bit(WORK_STRUCT_PENDING_BIT,
 177                                     work_data_bits(&cl->work)) ? "Q" : "",
 178                            r & CLOSURE_RUNNING  ? "R" : "");
 179
 180                 if (r & CLOSURE_WAITING)
 181                         seq_printf(f, " W %pS\n",
 182                                    (void *) cl->waiting_on);
 183
 184                 seq_printf(f, "\n");
 185         }
 186
 187         spin_unlock_irq(&closure_list_lock);
 188         return 0;
 189 }
 190
 191 DEFINE_SHOW_ATTRIBUTE(debug);
 192
 193 void  __init closure_debug_init(void)
 194 {
 195         if (!IS_ERR_OR_NULL(bcache_debug))
 196                 /*
 197                  * it is unnecessary to check return value of
 198                  * debugfs_create_file(), we should not care
 199                  * about this.
 200                  */
 201                 closure_debug = debugfs_create_file(
 202                         "closures", 0400, bcache_debug, NULL, &debug_fops);
 203 }
 204 #endif
 205
 206 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
 207 MODULE_LICENSE("GPL");