lib/closure.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Asynchronous refcounty things
   4  *
   5  * Copyright 2010, 2011 Kent Overstreet <[email protected]>
   6  * Copyright 2012 Google, Inc.
   7  */
   8
   9 #include <linux/closure.h>
  10 #include <linux/debugfs.h>
  11 #include <linux/export.h>
  12 #include <linux/rcupdate.h>
  13 #include <linux/seq_file.h>
  14 #include <linux/sched/debug.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                 smp_acquire__after_ctrl_dep();
  25
  26                 cl->closure_get_happened = false;
  27
  28                 if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
  29                         atomic_set(&cl->remaining,
  30                                    CLOSURE_REMAINING_INITIALIZER);
  31                         closure_queue(cl);
  32                 } else {
  33                         struct closure *parent = cl->parent;
  34                         closure_fn *destructor = cl->fn;
  35
  36                         closure_debug_destroy(cl);
  37
  38                         if (destructor)
  39                                 destructor(&cl->work);
  40
  41                         if (parent)
  42                                 closure_put(parent);
  43                 }
  44         }
  45 }
  46
  47 /* For clearing flags with the same atomic op as a put */
  48 void closure_sub(struct closure *cl, int v)
  49 {
  50         closure_put_after_sub(cl, atomic_sub_return_release(v, &cl->remaining));
  51 }
  52 EXPORT_SYMBOL(closure_sub);
  53
  54 /*
  55  * closure_put - decrement a closure's refcount
  56  */
  57 void closure_put(struct closure *cl)
  58 {
  59         closure_put_after_sub(cl, atomic_dec_return_release(&cl->remaining));
  60 }
  61 EXPORT_SYMBOL(closure_put);
  62
  63 /*
  64  * closure_wake_up - wake up all closures on a wait list, without memory barrier
  65  */
  66 void __closure_wake_up(struct closure_waitlist *wait_list)
  67 {
  68         struct llist_node *list;
  69         struct closure *cl, *t;
  70         struct llist_node *reverse = NULL;
  71
  72         list = llist_del_all(&wait_list->list);
  73
  74         /* We first reverse the list to preserve FIFO ordering and fairness */
  75         reverse = llist_reverse_order(list);
  76
  77         /* Then do the wakeups */
  78         llist_for_each_entry_safe(cl, t, reverse, list) {
  79                 closure_set_waiting(cl, 0);
  80                 closure_sub(cl, CLOSURE_WAITING + 1);
  81         }
  82 }
  83 EXPORT_SYMBOL(__closure_wake_up);
  84
  85 /**
  86  * closure_wait - add a closure to a waitlist
  87  * @waitlist: will own a ref on @cl, which will be released when
  88  * closure_wake_up() is called on @waitlist.
  89  * @cl: closure pointer.
  90  *
  91  */
  92 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
  93 {
  94         if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
  95                 return false;
  96
  97         cl->closure_get_happened = true;
  98         closure_set_waiting(cl, _RET_IP_);
  99         atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
 100         llist_add(&cl->list, &waitlist->list);
 101
 102         return true;
 103 }
 104 EXPORT_SYMBOL(closure_wait);
 105
 106 struct closure_syncer {
 107         struct task_struct      *task;
 108         int                     done;
 109 };
 110
 111 static CLOSURE_CALLBACK(closure_sync_fn)
 112 {
 113         struct closure *cl = container_of(ws, struct closure, work);
 114         struct closure_syncer *s = cl->s;
 115         struct task_struct *p;
 116
 117         rcu_read_lock();
 118         p = READ_ONCE(s->task);
 119         s->done = 1;
 120         wake_up_process(p);
 121         rcu_read_unlock();
 122 }
 123
 124 void __sched __closure_sync(struct closure *cl)
 125 {
 126         struct closure_syncer s = { .task = current };
 127
 128         cl->s = &s;
 129         continue_at(cl, closure_sync_fn, NULL);
 130
 131         while (1) {
 132                 set_current_state(TASK_UNINTERRUPTIBLE);
 133                 if (s.done)
 134                         break;
 135                 schedule();
 136         }
 137
 138         __set_current_state(TASK_RUNNING);
 139 }
 140 EXPORT_SYMBOL(__closure_sync);
 141
 142 int __sched __closure_sync_timeout(struct closure *cl, unsigned long timeout)
 143 {
 144         struct closure_syncer s = { .task = current };
 145         int ret = 0;
 146
 147         cl->s = &s;
 148         continue_at(cl, closure_sync_fn, NULL);
 149
 150         while (1) {
 151                 set_current_state(TASK_UNINTERRUPTIBLE);
 152                 if (s.done)
 153                         break;
 154                 if (!timeout) {
 155                         /*
 156                          * Carefully undo the continue_at() - but only if it
 157                          * hasn't completed, i.e. the final closure_put() hasn't
 158                          * happened yet:
 159                          */
 160                         unsigned old, new, v = atomic_read(&cl->remaining);
 161                         do {
 162                                 old = v;
 163                                 if (!old || (old & CLOSURE_RUNNING))
 164                                         goto success;
 165
 166                                 new = old + CLOSURE_REMAINING_INITIALIZER;
 167                         } while ((v = atomic_cmpxchg(&cl->remaining, old, new)) != old);
 168                         ret = -ETIME;
 169                 }
 170
 171                 timeout = schedule_timeout(timeout);
 172         }
 173 success:
 174         __set_current_state(TASK_RUNNING);
 175         return ret;
 176 }
 177 EXPORT_SYMBOL(__closure_sync_timeout);
 178
 179 #ifdef CONFIG_DEBUG_CLOSURES
 180
 181 static LIST_HEAD(closure_list);
 182 static DEFINE_SPINLOCK(closure_list_lock);
 183
 184 void closure_debug_create(struct closure *cl)
 185 {
 186         unsigned long flags;
 187
 188         BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
 189         cl->magic = CLOSURE_MAGIC_ALIVE;
 190
 191         spin_lock_irqsave(&closure_list_lock, flags);
 192         list_add(&cl->all, &closure_list);
 193         spin_unlock_irqrestore(&closure_list_lock, flags);
 194 }
 195 EXPORT_SYMBOL(closure_debug_create);
 196
 197 void closure_debug_destroy(struct closure *cl)
 198 {
 199         unsigned long flags;
 200
 201         BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
 202         cl->magic = CLOSURE_MAGIC_DEAD;
 203
 204         spin_lock_irqsave(&closure_list_lock, flags);
 205         list_del(&cl->all);
 206         spin_unlock_irqrestore(&closure_list_lock, flags);
 207 }
 208 EXPORT_SYMBOL(closure_debug_destroy);
 209
 210 static int debug_show(struct seq_file *f, void *data)
 211 {
 212         struct closure *cl;
 213
 214         spin_lock_irq(&closure_list_lock);
 215
 216         list_for_each_entry(cl, &closure_list, all) {
 217                 int r = atomic_read(&cl->remaining);
 218
 219                 seq_printf(f, "%p: %pS -> %pS p %p r %i ",
 220                            cl, (void *) cl->ip, cl->fn, cl->parent,
 221                            r & CLOSURE_REMAINING_MASK);
 222
 223                 seq_printf(f, "%s%s\n",
 224                            test_bit(WORK_STRUCT_PENDING_BIT,
 225                                     work_data_bits(&cl->work)) ? "Q" : "",
 226                            r & CLOSURE_RUNNING  ? "R" : "");
 227
 228                 if (r & CLOSURE_WAITING)
 229                         seq_printf(f, " W %pS\n",
 230                                    (void *) cl->waiting_on);
 231
 232                 seq_puts(f, "\n");
 233         }
 234
 235         spin_unlock_irq(&closure_list_lock);
 236         return 0;
 237 }
 238
 239 DEFINE_SHOW_ATTRIBUTE(debug);
 240
 241 static int __init closure_debug_init(void)
 242 {
 243         debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops);
 244         return 0;
 245 }
 246 late_initcall(closure_debug_init)
 247
 248 #endif