git.ozlabs.org Git - ccan/blob - ccan/io/poll.c

   1 /* Licensed under LGPLv2.1+ - see LICENSE file for details */
   2 #include "io.h"
   3 #include "backend.h"
   4 #include <assert.h>
   5 #include <poll.h>
   6 #include <stdlib.h>
   7 #include <sys/types.h>
   8 #include <sys/socket.h>
   9 #include <limits.h>
  10
  11 static size_t num_fds = 0, max_fds = 0, num_closing = 0, num_waiting = 0;
  12 static struct pollfd *pollfds = NULL;
  13 static struct fd **fds = NULL;
  14 static struct timers timeouts;
  15 #ifdef DEBUG
  16 static unsigned int io_loop_level;
  17 static struct io_conn *free_later;
  18 static void io_loop_enter(void)
  19 {
  20         io_loop_level++;
  21 }
  22 static void io_loop_exit(void)
  23 {
  24         io_loop_level--;
  25         if (io_loop_level == 0) {
  26                 /* Delayed free. */
  27                 while (free_later) {
  28                         struct io_conn *c = free_later;
  29                         free_later = c->finish_arg;
  30                         free(c);
  31                 }
  32         }
  33 }
  34 static void free_conn(struct io_conn *conn)
  35 {
  36         /* Only free on final exit: chain via finish. */
  37         if (io_loop_level > 1) {
  38                 struct io_conn *c;
  39                 for (c = free_later; c; c = c->finish_arg)
  40                         assert(c != conn);
  41                 conn->finish_arg = free_later;
  42                 free_later = conn;
  43         } else
  44                 free(conn);
  45 }
  46 #else
  47 static void io_loop_enter(void)
  48 {
  49 }
  50 static void io_loop_exit(void)
  51 {
  52 }
  53 static void free_conn(struct io_conn *conn)
  54 {
  55         free(conn);
  56 }
  57 #endif
  58
  59 static bool add_fd(struct fd *fd, short events)
  60 {
  61         if (num_fds + 1 > max_fds) {
  62                 struct pollfd *newpollfds;
  63                 struct fd **newfds;
  64                 size_t num = max_fds ? max_fds * 2 : 8;
  65
  66                 newpollfds = realloc(pollfds, sizeof(*newpollfds) * num);
  67                 if (!newpollfds)
  68                         return false;
  69                 pollfds = newpollfds;
  70                 newfds = realloc(fds, sizeof(*newfds) * num);
  71                 if (!newfds)
  72                         return false;
  73                 fds = newfds;
  74                 max_fds = num;
  75         }
  76
  77         pollfds[num_fds].events = events;
  78         /* In case it's idle. */
  79         if (!events)
  80                 pollfds[num_fds].fd = -fd->fd;
  81         else
  82                 pollfds[num_fds].fd = fd->fd;
  83         pollfds[num_fds].revents = 0; /* In case we're iterating now */
  84         fds[num_fds] = fd;
  85         fd->backend_info = num_fds;
  86         num_fds++;
  87         if (events)
  88                 num_waiting++;
  89
  90         return true;
  91 }
  92
  93 static void del_fd(struct fd *fd)
  94 {
  95         size_t n = fd->backend_info;
  96
  97         assert(n != -1);
  98         assert(n < num_fds);
  99         if (pollfds[n].events)
 100                 num_waiting--;
 101         if (n != num_fds - 1) {
 102                 /* Move last one over us. */
 103                 pollfds[n] = pollfds[num_fds-1];
 104                 fds[n] = fds[num_fds-1];
 105                 assert(fds[n]->backend_info == num_fds-1);
 106                 fds[n]->backend_info = n;
 107         } else if (num_fds == 1) {
 108                 /* Free everything when no more fds. */
 109                 free(pollfds);
 110                 free(fds);
 111                 pollfds = NULL;
 112                 fds = NULL;
 113                 max_fds = 0;
 114         }
 115         num_fds--;
 116         fd->backend_info = -1;
 117         close(fd->fd);
 118 }
 119
 120 bool add_listener(struct io_listener *l)
 121 {
 122         if (!add_fd(&l->fd, POLLIN))
 123                 return false;
 124         return true;
 125 }
 126
 127 void backend_plan_changed(struct io_conn *conn)
 128 {
 129         struct pollfd *pfd;
 130
 131         /* This can happen with debugging and delayed free... */
 132         if (conn->fd.backend_info == -1)
 133                 return;
 134
 135         pfd = &pollfds[conn->fd.backend_info];
 136
 137         if (pfd->events)
 138                 num_waiting--;
 139
 140         pfd->events = conn->plan.pollflag;
 141         if (conn->duplex) {
 142                 int mask = conn->duplex->plan.pollflag;
 143                 /* You can't *both* read/write. */
 144                 assert(!mask || pfd->events != mask);
 145                 pfd->events |= mask;
 146         }
 147         if (pfd->events) {
 148                 num_waiting++;
 149                 pfd->fd = conn->fd.fd;
 150         } else
 151                 pfd->fd = -conn->fd.fd;
 152
 153         if (!conn->plan.next)
 154                 num_closing++;
 155 }
 156
 157 bool add_conn(struct io_conn *c)
 158 {
 159         if (!add_fd(&c->fd, c->plan.pollflag))
 160                 return false;
 161         /* Immediate close is allowed. */
 162         if (!c->plan.next)
 163                 num_closing++;
 164         return true;
 165 }
 166
 167 bool add_duplex(struct io_conn *c)
 168 {
 169         c->fd.backend_info = c->duplex->fd.backend_info;
 170         backend_plan_changed(c);
 171         return true;
 172 }
 173
 174 static void del_conn(struct io_conn *conn)
 175 {
 176         if (conn->finish)
 177                 conn->finish(conn, conn->finish_arg);
 178         if (timeout_active(conn))
 179                 backend_del_timeout(conn);
 180         free(conn->timeout);
 181         if (conn->duplex) {
 182                 /* In case fds[] pointed to the other one. */
 183                 fds[conn->fd.backend_info] = &conn->duplex->fd;
 184                 conn->duplex->duplex = NULL;
 185                 conn->fd.backend_info = -1;
 186         } else
 187                 del_fd(&conn->fd);
 188         num_closing--;
 189 }
 190
 191 void del_listener(struct io_listener *l)
 192 {
 193         del_fd(&l->fd);
 194 }
 195
 196 static void set_plan(struct io_conn *conn, struct io_plan plan)
 197 {
 198         conn->plan = plan;
 199         backend_plan_changed(conn);
 200 }
 201
 202 static void accept_conn(struct io_listener *l)
 203 {
 204         int fd = accept(l->fd.fd, NULL, NULL);
 205
 206         /* FIXME: What to do here? */
 207         if (fd < 0)
 208                 return;
 209         l->init(fd, l->arg);
 210 }
 211
 212 /* It's OK to miss some, as long as we make progress. */
 213 static void finish_conns(void)
 214 {
 215         unsigned int i;
 216
 217         for (i = 0; !io_loop_return && i < num_fds; i++) {
 218                 struct io_conn *c, *duplex;
 219
 220                 if (!num_closing)
 221                         break;
 222
 223                 if (fds[i]->listener)
 224                         continue;
 225                 c = (void *)fds[i];
 226                 for (duplex = c->duplex; c; c = duplex, duplex = NULL) {
 227                         if (!c->plan.next) {
 228                                 del_conn(c);
 229                                 free_conn(c);
 230                                 i--;
 231                         }
 232                 }
 233         }
 234 }
 235
 236 void backend_add_timeout(struct io_conn *conn, struct timespec duration)
 237 {
 238         if (!timeouts.base)
 239                 timers_init(&timeouts, time_now());
 240         timer_add(&timeouts, &conn->timeout->timer,
 241                   time_add(time_now(), duration));
 242         conn->timeout->conn = conn;
 243 }
 244
 245 void backend_del_timeout(struct io_conn *conn)
 246 {
 247         assert(conn->timeout->conn == conn);
 248         timer_del(&timeouts, &conn->timeout->timer);
 249         conn->timeout->conn = NULL;
 250 }
 251
 252 /* This is the main loop. */
 253 void *io_loop(void)
 254 {
 255         void *ret;
 256
 257         io_loop_enter();
 258
 259         while (!io_loop_return) {
 260                 int i, r, timeout = INT_MAX;
 261                 struct timespec now;
 262                 bool some_timeouts = false;
 263
 264                 if (timeouts.base) {
 265                         struct timespec first;
 266                         struct list_head expired;
 267                         struct io_timeout *t;
 268
 269                         now = time_now();
 270
 271                         /* Call functions for expired timers. */
 272                         timers_expire(&timeouts, now, &expired);
 273                         while ((t = list_pop(&expired, struct io_timeout, timer.list))) {
 274                                 struct io_conn *conn = t->conn;
 275                                 /* Clear, in case timer re-adds */
 276                                 t->conn = NULL;
 277                                 set_current(conn);
 278                                 set_plan(conn, t->next(conn, t->next_arg));
 279                                 some_timeouts = true;
 280                         }
 281
 282                         /* Now figure out how long to wait for the next one. */
 283                         if (timer_earliest(&timeouts, &first)) {
 284                                 uint64_t f = time_to_msec(time_sub(first, now));
 285                                 if (f < INT_MAX)
 286                                         timeout = f;
 287                         }
 288                 }
 289
 290                 if (num_closing) {
 291                         finish_conns();
 292                         /* Could have started/finished more. */
 293                         continue;
 294                 }
 295
 296                 /* debug can recurse on io_loop; anything can change. */
 297                 if (doing_debug() && some_timeouts)
 298                         continue;
 299
 300                 if (num_fds == 0)
 301                         break;
 302
 303                 /* You can't tell them all to go to sleep! */
 304                 assert(num_waiting);
 305
 306                 r = poll(pollfds, num_fds, timeout);
 307                 if (r < 0)
 308                         break;
 309
 310                 for (i = 0; i < num_fds && !io_loop_return; i++) {
 311                         struct io_conn *c = (void *)fds[i];
 312                         int events = pollfds[i].revents;
 313
 314                         if (r == 0)
 315                                 break;
 316
 317                         if (fds[i]->listener) {
 318                                 if (events & POLLIN) {
 319                                         accept_conn((void *)c);
 320                                         r--;
 321                                 }
 322                         } else if (events & (POLLIN|POLLOUT)) {
 323                                 r--;
 324                                 if (c->duplex) {
 325                                         int mask = c->duplex->plan.pollflag;
 326                                         if (events & mask) {
 327                                                 io_ready(c->duplex);
 328                                                 events &= ~mask;
 329                                                 /* debug can recurse;
 330                                                  * anything can change. */
 331                                                 if (doing_debug())
 332                                                         break;
 333                                                 if (!(events&(POLLIN|POLLOUT)))
 334                                                         continue;
 335                                         }
 336                                 }
 337                                 io_ready(c);
 338                                 /* debug can recurse; anything can change. */
 339                                 if (doing_debug())
 340                                         break;
 341                         } else if (events & POLLHUP) {
 342                                 r--;
 343                                 set_current(c);
 344                                 set_plan(c, io_close(c, NULL));
 345                                 if (c->duplex) {
 346                                         set_current(c->duplex);
 347                                         set_plan(c->duplex,
 348                                                  io_close(c->duplex, NULL));
 349                                 }
 350                         }
 351                 }
 352         }
 353
 354         while (num_closing)
 355                 finish_conns();
 356
 357         ret = io_loop_return;
 358         io_loop_return = NULL;
 359
 360         io_loop_exit();
 361         return ret;
 362 }