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 void waitset_destroy(struct waitset *set)
  61 {
  62         talloc_free(set);
  63 }
  64
  65 static struct waiter *waiter_new(struct waitset *set)
  66 {
  67         struct waiter **waiters, *waiter;
  68
  69         waiter = talloc(set->waiters, struct waiter);
  70         if (!waiter)
  71                 return NULL;
  72
  73         waiters = talloc_realloc(set, set->waiters,
  74                         struct waiter *, set->n_waiters + 1);
  75
  76         if (!waiters) {
  77                 talloc_free(waiter);
  78                 return NULL;
  79         }
  80
  81         set->waiters_changed = true;
  82         set->waiters = waiters;
  83         set->n_waiters++;
  84
  85         set->waiters[set->n_waiters - 1] = waiter;
  86         waiter->active = true;
  87         return waiter;
  88 }
  89
  90 struct waiter *waiter_register_io(struct waitset *set, int fd, int events,
  91                 waiter_cb callback, void *arg)
  92 {
  93         struct waiter *waiter = waiter_new(set);
  94
  95         waiter->type = WAITER_IO;
  96         waiter->set = set;
  97         waiter->io.fd = fd;
  98         waiter->io.events = events;
  99         waiter->callback = callback;
 100         waiter->arg = arg;
 101
 102         return waiter;
 103 }
 104
 105 struct waiter *waiter_register_timeout(struct waitset *set, int delay_ms,
 106                 waiter_cb callback, void *arg)
 107 {
 108         struct waiter *waiter = waiter_new(set);
 109         struct timeval now, delay;
 110
 111         delay.tv_sec = delay_ms / 1000;
 112         delay.tv_usec = 1000 * (delay_ms % 1000);
 113
 114         gettimeofday(&now, NULL);
 115
 116         timeradd(&now, &delay, &waiter->timeout);
 117
 118         waiter->type = WAITER_TIME;
 119         waiter->set = set;
 120         waiter->callback = callback;
 121         waiter->arg = arg;
 122
 123         return waiter;
 124 }
 125
 126 void waiter_remove(struct waiter *waiter)
 127 {
 128         struct waitset *set = waiter->set;
 129         int i;
 130
 131         for (i = 0; i < set->n_waiters; i++)
 132                 if (set->waiters[i] == waiter)
 133                         break;
 134
 135         assert(i < set->n_waiters);
 136
 137         set->n_waiters--;
 138         memmove(&set->waiters[i], &set->waiters[i+1],
 139                 (set->n_waiters - i) * sizeof(set->waiters[0]));
 140
 141         set->waiters = talloc_realloc(set, set->waiters,
 142                         struct waiter *, set->n_waiters);
 143         set->waiters_changed = true;
 144
 145         waiter->active = false;
 146         list_add(&set->free_list, &waiter->list);
 147 }
 148
 149 static void update_waiters(struct waitset *set)
 150 {
 151         int n_io, n_time, i_io, i_time, i;
 152
 153         if (!set->waiters_changed)
 154                 return;
 155
 156         n_io = n_time = 0;
 157
 158         for (i = 0; i < set->n_waiters; i++) {
 159                 if (set->waiters[i]->type == WAITER_IO)
 160                         n_io++;
 161                 else if (set->waiters[i]->type == WAITER_TIME)
 162                         n_time++;
 163         }
 164
 165         /* realloc if counts have changed */
 166         if (set->n_io_waiters != n_io) {
 167                 set->io_waiters = talloc_realloc(set, set->io_waiters,
 168                                 struct waiter *, n_io);
 169                 set->pollfds = talloc_realloc(set, set->pollfds,
 170                                 struct pollfd, n_io);
 171                 set->n_io_waiters = n_io;
 172         }
 173         if (set->n_time_waiters != n_time) {
 174                 set->time_waiters = talloc_realloc(set, set->time_waiters,
 175                                 struct waiter *, n_time);
 176                 set->n_time_waiters = n_time;
 177         }
 178
 179         i_io = 0;
 180         i_time = 0;
 181
 182         timerclear(&set->next_timeout);
 183
 184         for (i = 0; i < set->n_waiters; i++) {
 185                 struct waiter *waiter = set->waiters[i];
 186
 187                 /* IO waiters: copy to io_waiters, populate pollfds */
 188                 if (waiter->type == WAITER_IO) {
 189                         set->pollfds[i_io].fd = waiter->io.fd;
 190                         set->pollfds[i_io].events = waiter->io.events;
 191                         set->io_waiters[i_io] = waiter;
 192                         i_io++;
 193                 }
 194
 195                 /* time waiters: copy to time_waiters, calculate next expiry */
 196                 if (waiter->type == WAITER_TIME) {
 197                         if (!timerisset(&set->next_timeout) ||
 198                                         timercmp(&waiter->timeout,
 199                                                 &set->next_timeout, <))
 200                                 set->next_timeout = waiter->timeout;
 201
 202                         set->time_waiters[i_time] = waiter;
 203                         i_time++;
 204                 }
 205         }
 206 }
 207
 208 int waiter_poll(struct waitset *set)
 209 {
 210         struct timeval now, timeout;
 211         struct waiter *waiter, *tmp;
 212         int timeout_ms;
 213         int i, rc;
 214
 215         /* If the waiters have been updated, we need to update our
 216          * consistent copy */
 217         update_waiters(set);
 218
 219         if (timerisset(&set->next_timeout)) {
 220                 gettimeofday(&now, NULL);
 221                 timersub(&set->next_timeout, &now, &timeout);
 222                 timeout_ms = timeout.tv_sec * 1000 +
 223                                 timeout.tv_usec / 1000;
 224                 if (timeout_ms < 0)
 225                         timeout_ms = 0;
 226         } else {
 227                 timeout_ms = -1;
 228         }
 229
 230
 231         rc = poll(set->pollfds, set->n_io_waiters, timeout_ms);
 232
 233         if (rc < 0)
 234                 goto out;
 235
 236         for (i = 0; i < set->n_io_waiters; i++) {
 237                 struct waiter *waiter = set->io_waiters[i];
 238
 239                 if (!waiter->active)
 240                         continue;
 241
 242                 if (!set->pollfds[i].revents)
 243                         continue;
 244                 rc = waiter->callback(waiter->arg);
 245
 246                 if (rc)
 247                         waiter_remove(waiter);
 248         }
 249
 250         if (set->n_time_waiters > 0)
 251                 gettimeofday(&now, NULL);
 252
 253         for (i = 0; i < set->n_time_waiters; i++) {
 254                 struct waiter *waiter = set->time_waiters[i];
 255
 256                 if (!waiter->active)
 257                         continue;
 258
 259                 if (timercmp(&waiter->timeout, &now, >))
 260                         continue;
 261
 262                 waiter->callback(waiter->arg);
 263
 264                 waiter_remove(waiter);
 265         }
 266
 267         rc = 0;
 268
 269 out:
 270         /* free any waiters that have been removed */
 271         list_for_each_entry_safe(&set->free_list, waiter, tmp, list)
 272                 talloc_free(waiter);
 273         list_init(&set->free_list);
 274
 275         return rc;
 276 }