lib/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/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);
  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 void closure_sync_fn(struct closure *cl)
 112 {
 113         struct closure_syncer *s = cl->s;
 114         struct task_struct *p;
 115
 116         rcu_read_lock();
 117         p = READ_ONCE(s->task);
 118         s->done = 1;
 119         wake_up_process(p);
 120         rcu_read_unlock();
 121 }
 122
 123 void __sched __closure_sync(struct closure *cl)
 124 {
 125         struct closure_syncer s = { .task = current };
 126
 127         cl->s = &s;
 128         continue_at(cl, closure_sync_fn, NULL);
 129
 130         while (1) {
 131                 set_current_state(TASK_UNINTERRUPTIBLE);
 132                 if (s.done)
 133                         break;
 134                 schedule();
 135         }
 136
 137         __set_current_state(TASK_RUNNING);
 138 }
 139 EXPORT_SYMBOL(__closure_sync);
 140
 141 #ifdef CONFIG_DEBUG_CLOSURES
 142
 143 static LIST_HEAD(closure_list);
 144 static DEFINE_SPINLOCK(closure_list_lock);
 145
 146 void closure_debug_create(struct closure *cl)
 147 {
 148         unsigned long flags;
 149
 150         BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
 151         cl->magic = CLOSURE_MAGIC_ALIVE;
 152
 153         spin_lock_irqsave(&closure_list_lock, flags);
 154         list_add(&cl->all, &closure_list);
 155         spin_unlock_irqrestore(&closure_list_lock, flags);
 156 }
 157 EXPORT_SYMBOL(closure_debug_create);
 158
 159 void closure_debug_destroy(struct closure *cl)
 160 {
 161         unsigned long flags;
 162
 163         BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
 164         cl->magic = CLOSURE_MAGIC_DEAD;
 165
 166         spin_lock_irqsave(&closure_list_lock, flags);
 167         list_del(&cl->all);
 168         spin_unlock_irqrestore(&closure_list_lock, flags);
 169 }
 170 EXPORT_SYMBOL(closure_debug_destroy);
 171
 172 static int debug_show(struct seq_file *f, void *data)
 173 {
 174         struct closure *cl;
 175
 176         spin_lock_irq(&closure_list_lock);
 177
 178         list_for_each_entry(cl, &closure_list, all) {
 179                 int r = atomic_read(&cl->remaining);
 180
 181                 seq_printf(f, "%p: %pS -> %pS p %p r %i ",
 182                            cl, (void *) cl->ip, cl->fn, cl->parent,
 183                            r & CLOSURE_REMAINING_MASK);
 184
 185                 seq_printf(f, "%s%s\n",
 186                            test_bit(WORK_STRUCT_PENDING_BIT,
 187                                     work_data_bits(&cl->work)) ? "Q" : "",
 188                            r & CLOSURE_RUNNING  ? "R" : "");
 189
 190                 if (r & CLOSURE_WAITING)
 191                         seq_printf(f, " W %pS\n",
 192                                    (void *) cl->waiting_on);
 193
 194                 seq_puts(f, "\n");
 195         }
 196
 197         spin_unlock_irq(&closure_list_lock);
 198         return 0;
 199 }
 200
 201 DEFINE_SHOW_ATTRIBUTE(debug);
 202
 203 static int __init closure_debug_init(void)
 204 {
 205         debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops);
 206         return 0;
 207 }
 208 late_initcall(closure_debug_init)
 209
 210 #endif