git.ozlabs.org Git - petitboot/blob - lib/waiter/waiter.c

   1
   2 #include <poll.h>
   3 #include <stdbool.h>
   4 #include <string.h>
   5 #include <assert.h>
   6 #include <sys/time.h>
   7
   8 #include <talloc/talloc.h>
   9 #include <list/list.h>
  10
  11 #include "waiter.h"
  12
  13 struct waiter {
  14         struct waitset  *set;
  15         enum {
  16                 WAITER_IO,
  17                 WAITER_TIME,
  18         } type;
  19         union {
  20                 struct {
  21                         int     fd;
  22                         int     events;
  23                 } io;
  24                 struct timeval  timeout;
  25         };
  26         waiter_cb       callback;
  27         void            *arg;
  28
  29         bool                    active;
  30         struct list_item        list;
  31 };
  32
  33 struct waitset {
  34         struct waiter   **waiters;
  35         int             n_waiters;
  36         bool            waiters_changed;
  37
  38         struct timeval  next_timeout;
  39
  40         /* These are kept consistent over each call to waiter_poll, as
  41          * set->waiters may be updated (by waiters' callbacks calling
  42          * waiter_register or waiter_remove) during iteration. */
  43         struct pollfd   *pollfds;
  44         int             n_pollfds;
  45         struct waiter   **io_waiters;
  46         int             n_io_waiters;
  47         struct waiter   **time_waiters;
  48         int             n_time_waiters;
  49
  50         struct list     free_list;
  51 };
  52
  53 struct waitset *waitset_create(void *ctx)
  54 {
  55         struct waitset *set = talloc_zero(ctx, struct waitset);
  56         list_init(&set->free_list);
  57         return set;
  58 }
  59
  60 static struct waiter *waiter_new(struct waitset *set)
  61 {
  62         struct waiter **waiters, *waiter;
  63
  64         waiter = talloc(set, struct waiter);
  65         if (!waiter)
  66                 return NULL;
  67
  68         waiters = talloc_realloc(set, set->waiters,
  69                         struct waiter *, set->n_waiters + 1);
  70
  71         if (!waiters) {
  72                 talloc_free(waiter);
  73                 return NULL;
  74         }
  75
  76         set->waiters_changed = true;
  77         set->waiters = waiters;
  78         set->n_waiters++;
  79
  80         set->waiters[set->n_waiters - 1] = waiter;
  81         waiter->active = true;
  82         return waiter;
  83 }
  84
  85 struct waiter *waiter_register_io(struct waitset *set, int fd, int events,
  86                 waiter_cb callback, void *arg)
  87 {
  88         struct waiter *waiter = waiter_new(set);
  89
  90         waiter->type = WAITER_IO;
  91         waiter->set = set;
  92         waiter->io.fd = fd;
  93         waiter->io.events = events;
  94         waiter->callback = callback;
  95         waiter->arg = arg;
  96
  97         return waiter;
  98 }
  99
 100 struct waiter *waiter_register_timeout(struct waitset *set, int delay_ms,
 101                 waiter_cb callback, void *arg)
 102 {
 103         struct waiter *waiter = waiter_new(set);
 104         struct timeval now, delay;
 105
 106         delay.tv_sec = delay_ms / 1000;
 107         delay.tv_usec = 1000 * (delay_ms % 1000);
 108
 109         gettimeofday(&now, NULL);
 110
 111         timeradd(&now, &delay, &waiter->timeout);
 112
 113         waiter->type = WAITER_TIME;
 114         waiter->set = set;
 115         waiter->callback = callback;
 116         waiter->arg = arg;
 117
 118         return waiter;
 119 }
 120
 121 void waiter_remove(struct waiter *waiter)
 122 {
 123         struct waitset *set = waiter->set;
 124         int i;
 125
 126         for (i = 0; i < set->n_waiters; i++)
 127                 if (set->waiters[i] == waiter)
 128                         break;
 129
 130         assert(i < set->n_waiters);
 131
 132         set->n_waiters--;
 133         memmove(&set->waiters[i], &set->waiters[i+1],
 134                 (set->n_waiters - i) * sizeof(set->waiters[0]));
 135
 136         set->waiters = talloc_realloc(set, set->waiters,
 137                         struct waiter *, set->n_waiters);
 138         set->waiters_changed = true;
 139
 140         waiter->active = false;
 141         list_add(&set->free_list, &waiter->list);
 142 }
 143
 144 static void update_waiters(struct waitset *set)
 145 {
 146         int n_io, n_time, i_io, i_time, i;
 147
 148         if (!set->waiters_changed)
 149                 return;
 150
 151         n_io = n_time = 0;
 152
 153         for (i = 0; i < set->n_waiters; i++) {
 154                 if (set->waiters[i]->type == WAITER_IO)
 155                         n_io++;
 156                 else if (set->waiters[i]->type == WAITER_TIME)
 157                         n_time++;
 158         }
 159
 160         /* realloc if counts have changed */
 161         if (set->n_io_waiters != n_io) {
 162                 set->io_waiters = talloc_realloc(set, set->io_waiters,
 163                                 struct waiter *, n_io);
 164                 set->pollfds = talloc_realloc(set, set->pollfds,
 165                                 struct pollfd, n_io);
 166                 set->n_io_waiters = n_io;
 167         }
 168         if (set->n_time_waiters != n_time) {
 169                 set->time_waiters = talloc_realloc(set, set->time_waiters,
 170                                 struct waiter *, n_time);
 171                 set->n_time_waiters = n_time;
 172         }
 173
 174         i_io = 0;
 175         i_time = 0;
 176
 177         timerclear(&set->next_timeout);
 178
 179         for (i = 0; i < set->n_waiters; i++) {
 180                 struct waiter *waiter = set->waiters[i];
 181
 182                 /* IO waiters: copy to io_waiters, populate pollfds */
 183                 if (waiter->type == WAITER_IO) {
 184                         set->pollfds[i_io].fd = waiter->io.fd;
 185                         set->pollfds[i_io].events = waiter->io.events;
 186                         set->io_waiters[i_io] = waiter;
 187                         i_io++;
 188                 }
 189
 190                 /* time waiters: copy to time_waiters, calculate next expiry */
 191                 if (waiter->type == WAITER_TIME) {
 192                         if (!timerisset(&set->next_timeout) ||
 193                                         timercmp(&waiter->timeout,
 194                                                 &set->next_timeout, <))
 195                                 set->next_timeout = waiter->timeout;
 196
 197                         set->time_waiters[i_time] = waiter;
 198                         i_time++;
 199                 }
 200         }
 201 }
 202
 203 int waiter_poll(struct waitset *set)
 204 {
 205         struct timeval now, timeout;
 206         struct waiter *waiter, *tmp;
 207         int timeout_ms;
 208         int i, rc;
 209
 210         /* If the waiters have been updated, we need to update our
 211          * consistent copy */
 212         update_waiters(set);
 213
 214         if (timerisset(&set->next_timeout)) {
 215                 gettimeofday(&now, NULL);
 216                 timersub(&set->next_timeout, &now, &timeout);
 217                 timeout_ms = timeout.tv_sec * 1000 +
 218                                 timeout.tv_usec / 1000;
 219                 if (timeout_ms < 0)
 220                         timeout_ms = 0;
 221         } else {
 222                 timeout_ms = -1;
 223         }
 224
 225
 226         rc = poll(set->pollfds, set->n_io_waiters, timeout_ms);
 227
 228         if (rc < 0)
 229                 goto out;
 230
 231         for (i = 0; i < set->n_io_waiters; i++) {
 232                 struct waiter *waiter = set->io_waiters[i];
 233
 234                 if (!waiter->active)
 235                         continue;
 236
 237                 if (!set->pollfds[i].revents)
 238                         continue;
 239                 rc = waiter->callback(waiter->arg);
 240
 241                 if (rc)
 242                         waiter_remove(waiter);
 243         }
 244
 245         if (set->n_time_waiters > 0)
 246                 gettimeofday(&now, NULL);
 247
 248         for (i = 0; i < set->n_time_waiters; i++) {
 249                 struct waiter *waiter = set->time_waiters[i];
 250
 251                 if (!waiter->active)
 252                         continue;
 253
 254                 if (timercmp(&waiter->timeout, &now, >))
 255                         continue;
 256
 257                 waiter->callback(waiter->arg);
 258
 259                 waiter_remove(waiter);
 260         }
 261
 262         rc = 0;
 263
 264 out:
 265         /* free any waiters that have been removed */
 266         list_for_each_entry_safe(&set->free_list, waiter, tmp, list)
 267                 talloc_free(waiter);
 268         list_init(&set->free_list);
 269
 270         return rc;
 271 }