epoll.c

   1 /*
   2  * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
   3  * Copyright 2007-2012 Niels Provos, Nick Mathewson
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. The name of the author may not be used to endorse or promote products
  14  *    derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27 #include "event2/event-config.h"
  28 #include "evconfig-private.h"
  29
  30 #ifdef EVENT__HAVE_EPOLL
  31
  32 #include <stdint.h>
  33 #include <sys/types.h>
  34 #include <sys/resource.h>
  35 #ifdef EVENT__HAVE_SYS_TIME_H
  36 #include <sys/time.h>
  37 #endif
  38 #include <sys/queue.h>
  39 #include <sys/epoll.h>
  40 #include <signal.h>
  41 #include <limits.h>
  42 #include <stdio.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <unistd.h>
  46 #include <errno.h>
  47 #ifdef EVENT__HAVE_FCNTL_H
  48 #include <fcntl.h>
  49 #endif
  50 #ifdef EVENT__HAVE_SYS_TIMERFD_H
  51 #include <sys/timerfd.h>
  52 #endif
  53
  54 #include "event-internal.h"
  55 #include "evsignal-internal.h"
  56 #include "event2/thread.h"
  57 #include "evthread-internal.h"
  58 #include "log-internal.h"
  59 #include "evmap-internal.h"
  60 #include "changelist-internal.h"
  61 #include "time-internal.h"
  62
  63 /* Since Linux 2.6.17, epoll is able to report about peer half-closed connection
  64    using special EPOLLRDHUP flag on a read event.
  65 */
  66 #if !defined(EPOLLRDHUP)
  67 #define EPOLLRDHUP 0
  68 #define EARLY_CLOSE_IF_HAVE_RDHUP 0
  69 #else
  70 #define EARLY_CLOSE_IF_HAVE_RDHUP EV_FEATURE_EARLY_CLOSE
  71 #endif
  72
  73 #include "epolltable-internal.h"
  74
  75 #if defined(EVENT__HAVE_SYS_TIMERFD_H) &&                         \
  76         defined(EVENT__HAVE_TIMERFD_CREATE) &&                    \
  77         defined(HAVE_POSIX_MONOTONIC) && defined(TFD_NONBLOCK) && \
  78         defined(TFD_CLOEXEC)
  79 /* Note that we only use timerfd if TFD_NONBLOCK and TFD_CLOEXEC are available
  80    and working.  This means that we can't support it on 2.6.25 (where timerfd
  81    was introduced) or 2.6.26, since 2.6.27 introduced those flags.
  82  */
  83 #define USING_TIMERFD
  84 #endif
  85
  86 struct epollop {
  87         struct epoll_event *events;
  88         int nevents;
  89         int epfd;
  90 #ifdef USING_TIMERFD
  91         int timerfd;
  92 #endif
  93 };
  94
  95 static void *epoll_init(struct event_base *);
  96 static int epoll_dispatch(struct event_base *, struct timeval *);
  97 static void epoll_dealloc(struct event_base *);
  98
  99 static const struct eventop epollops_changelist = {
 100         "epoll (with changelist)",
 101         epoll_init,
 102         event_changelist_add_,
 103         event_changelist_del_,
 104         epoll_dispatch,
 105         epoll_dealloc,
 106         1, /* need reinit */
 107         EV_FEATURE_ET|EV_FEATURE_O1| EARLY_CLOSE_IF_HAVE_RDHUP,
 108         EVENT_CHANGELIST_FDINFO_SIZE
 109 };
 110
 111
 112 static int epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd,
 113     short old, short events, void *p);
 114 static int epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd,
 115     short old, short events, void *p);
 116
 117 const struct eventop epollops = {
 118         "epoll",
 119         epoll_init,
 120         epoll_nochangelist_add,
 121         epoll_nochangelist_del,
 122         epoll_dispatch,
 123         epoll_dealloc,
 124         1, /* need reinit */
 125         EV_FEATURE_ET|EV_FEATURE_O1|EV_FEATURE_EARLY_CLOSE,
 126         0
 127 };
 128
 129 #define INITIAL_NEVENT 32
 130 #define MAX_NEVENT 4096
 131
 132 /* On Linux kernels at least up to 2.6.24.4, epoll can't handle timeout
 133  * values bigger than (LONG_MAX - 999ULL)/HZ.  HZ in the wild can be
 134  * as big as 1000, and LONG_MAX can be as small as (1<<31)-1, so the
 135  * largest number of msec we can support here is 2147482.  Let's
 136  * round that down by 47 seconds.
 137  */
 138 #define MAX_EPOLL_TIMEOUT_MSEC (35*60*1000)
 139
 140 static void *
 141 epoll_init(struct event_base *base)
 142 {
 143         int epfd = -1;
 144         struct epollop *epollop;
 145
 146 #ifdef EVENT__HAVE_EPOLL_CREATE1
 147         /* First, try the shiny new epoll_create1 interface, if we have it. */
 148         epfd = epoll_create1(EPOLL_CLOEXEC);
 149 #endif
 150         if (epfd == -1) {
 151                 /* Initialize the kernel queue using the old interface.  (The
 152                 size field is ignored   since 2.6.8.) */
 153                 if ((epfd = epoll_create(32000)) == -1) {
 154                         if (errno != ENOSYS)
 155                                 event_warn("epoll_create");
 156                         return (NULL);
 157                 }
 158                 evutil_make_socket_closeonexec(epfd);
 159         }
 160
 161         if (!(epollop = mm_calloc(1, sizeof(struct epollop)))) {
 162                 close(epfd);
 163                 return (NULL);
 164         }
 165
 166         epollop->epfd = epfd;
 167
 168         /* Initialize fields */
 169         epollop->events = mm_calloc(INITIAL_NEVENT, sizeof(struct epoll_event));
 170         if (epollop->events == NULL) {
 171                 mm_free(epollop);
 172                 close(epfd);
 173                 return (NULL);
 174         }
 175         epollop->nevents = INITIAL_NEVENT;
 176
 177         if ((base->flags & EVENT_BASE_FLAG_EPOLL_USE_CHANGELIST) != 0 ||
 178             ((base->flags & EVENT_BASE_FLAG_IGNORE_ENV) == 0 &&
 179                 evutil_getenv_("EVENT_EPOLL_USE_CHANGELIST") != NULL)) {
 180
 181                 base->evsel = &epollops_changelist;
 182         }
 183
 184 #ifdef USING_TIMERFD
 185         /*
 186           The epoll interface ordinarily gives us one-millisecond precision,
 187           so on Linux it makes perfect sense to use the CLOCK_MONOTONIC_COARSE
 188           timer.  But when the user has set the new PRECISE_TIMER flag for an
 189           event_base, we can try to use timerfd to give them finer granularity.
 190         */
 191         if ((base->flags & EVENT_BASE_FLAG_PRECISE_TIMER) &&
 192             base->monotonic_timer.monotonic_clock == CLOCK_MONOTONIC) {
 193                 int fd;
 194                 fd = epollop->timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC);
 195                 if (epollop->timerfd >= 0) {
 196                         struct epoll_event epev;
 197                         memset(&epev, 0, sizeof(epev));
 198                         epev.data.fd = epollop->timerfd;
 199                         epev.events = EPOLLIN;
 200                         if (epoll_ctl(epollop->epfd, EPOLL_CTL_ADD, fd, &epev) < 0) {
 201                                 event_warn("epoll_ctl(timerfd)");
 202                                 close(fd);
 203                                 epollop->timerfd = -1;
 204                         }
 205                 } else {
 206                         if (errno != EINVAL && errno != ENOSYS) {
 207                                 /* These errors probably mean that we were
 208                                  * compiled with timerfd/TFD_* support, but
 209                                  * we're running on a kernel that lacks those.
 210                                  */
 211                                 event_warn("timerfd_create");
 212                         }
 213                         epollop->timerfd = -1;
 214                 }
 215         } else {
 216                 epollop->timerfd = -1;
 217         }
 218 #endif
 219
 220         evsig_init_(base);
 221
 222         return (epollop);
 223 }
 224
 225 static const char *
 226 change_to_string(int change)
 227 {
 228         change &= (EV_CHANGE_ADD|EV_CHANGE_DEL);
 229         if (change == EV_CHANGE_ADD) {
 230                 return "add";
 231         } else if (change == EV_CHANGE_DEL) {
 232                 return "del";
 233         } else if (change == 0) {
 234                 return "none";
 235         } else {
 236                 return "???";
 237         }
 238 }
 239
 240 static const char *
 241 epoll_op_to_string(int op)
 242 {
 243         return op == EPOLL_CTL_ADD?"ADD":
 244             op == EPOLL_CTL_DEL?"DEL":
 245             op == EPOLL_CTL_MOD?"MOD":
 246             "???";
 247 }
 248
 249 #define PRINT_CHANGES(op, events, ch, status)  \
 250         "Epoll %s(%d) on fd %d " status ". "       \
 251         "Old events were %d; "                     \
 252         "read change was %d (%s); "                \
 253         "write change was %d (%s); "               \
 254         "close change was %d (%s)",                \
 255         epoll_op_to_string(op),                    \
 256         events,                                    \
 257         ch->fd,                                    \
 258         ch->old_events,                            \
 259         ch->read_change,                           \
 260         change_to_string(ch->read_change),         \
 261         ch->write_change,                          \
 262         change_to_string(ch->write_change),        \
 263         ch->close_change,                          \
 264         change_to_string(ch->close_change)
 265
 266 static int
 267 epoll_apply_one_change(struct event_base *base,
 268     struct epollop *epollop,
 269     const struct event_change *ch)
 270 {
 271         struct epoll_event epev;
 272         int op, events = 0;
 273         int idx;
 274
 275         idx = EPOLL_OP_TABLE_INDEX(ch);
 276         op = epoll_op_table[idx].op;
 277         events = epoll_op_table[idx].events;
 278
 279         if (!events) {
 280                 EVUTIL_ASSERT(op == 0);
 281                 return 0;
 282         }
 283
 284         if ((ch->read_change|ch->write_change) & EV_CHANGE_ET)
 285                 events |= EPOLLET;
 286
 287         memset(&epev, 0, sizeof(epev));
 288         epev.data.fd = ch->fd;
 289         epev.events = events;
 290         if (epoll_ctl(epollop->epfd, op, ch->fd, &epev) == 0) {
 291                 event_debug((PRINT_CHANGES(op, epev.events, ch, "okay")));
 292                 return 0;
 293         }
 294
 295         switch (op) {
 296         case EPOLL_CTL_MOD:
 297                 if (errno == ENOENT) {
 298                         /* If a MOD operation fails with ENOENT, the
 299                          * fd was probably closed and re-opened.  We
 300                          * should retry the operation as an ADD.
 301                          */
 302                         if (epoll_ctl(epollop->epfd, EPOLL_CTL_ADD, ch->fd, &epev) == -1) {
 303                                 event_warn("Epoll MOD(%d) on %d retried as ADD; that failed too",
 304                                     (int)epev.events, ch->fd);
 305                                 return -1;
 306                         } else {
 307                                 event_debug(("Epoll MOD(%d) on %d retried as ADD; succeeded.",
 308                                         (int)epev.events,
 309                                         ch->fd));
 310                                 return 0;
 311                         }
 312                 }
 313                 break;
 314         case EPOLL_CTL_ADD:
 315                 if (errno == EEXIST) {
 316                         /* If an ADD operation fails with EEXIST,
 317                          * either the operation was redundant (as with a
 318                          * precautionary add), or we ran into a fun
 319                          * kernel bug where using dup*() to duplicate the
 320                          * same file into the same fd gives you the same epitem
 321                          * rather than a fresh one.  For the second case,
 322                          * we must retry with MOD. */
 323                         if (epoll_ctl(epollop->epfd, EPOLL_CTL_MOD, ch->fd, &epev) == -1) {
 324                                 event_warn("Epoll ADD(%d) on %d retried as MOD; that failed too",
 325                                     (int)epev.events, ch->fd);
 326                                 return -1;
 327                         } else {
 328                                 event_debug(("Epoll ADD(%d) on %d retried as MOD; succeeded.",
 329                                         (int)epev.events,
 330                                         ch->fd));
 331                                 return 0;
 332                         }
 333                 }
 334                 break;
 335         case EPOLL_CTL_DEL:
 336                 if (errno == ENOENT || errno == EBADF || errno == EPERM) {
 337                         /* If a delete fails with one of these errors,
 338                          * that's fine too: we closed the fd before we
 339                          * got around to calling epoll_dispatch. */
 340                         event_debug(("Epoll DEL(%d) on fd %d gave %s: DEL was unnecessary.",
 341                                 (int)epev.events,
 342                                 ch->fd,
 343                                 strerror(errno)));
 344                         return 0;
 345                 }
 346                 break;
 347         default:
 348                 break;
 349         }
 350
 351         event_warn(PRINT_CHANGES(op, epev.events, ch, "failed"));
 352         return -1;
 353 }
 354
 355 static int
 356 epoll_apply_changes(struct event_base *base)
 357 {
 358         struct event_changelist *changelist = &base->changelist;
 359         struct epollop *epollop = base->evbase;
 360         struct event_change *ch;
 361
 362         int r = 0;
 363         int i;
 364
 365         for (i = 0; i < changelist->n_changes; ++i) {
 366                 ch = &changelist->changes[i];
 367                 if (epoll_apply_one_change(base, epollop, ch) < 0)
 368                         r = -1;
 369         }
 370
 371         return (r);
 372 }
 373
 374 static int
 375 epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd,
 376     short old, short events, void *p)
 377 {
 378         struct event_change ch;
 379         ch.fd = fd;
 380         ch.old_events = old;
 381         ch.read_change = ch.write_change = ch.close_change = 0;
 382         if (events & EV_WRITE)
 383                 ch.write_change = EV_CHANGE_ADD |
 384                     (events & EV_ET);
 385         if (events & EV_READ)
 386                 ch.read_change = EV_CHANGE_ADD |
 387                     (events & EV_ET);
 388         if (events & EV_CLOSED)
 389                 ch.close_change = EV_CHANGE_ADD |
 390                     (events & EV_ET);
 391
 392         return epoll_apply_one_change(base, base->evbase, &ch);
 393 }
 394
 395 static int
 396 epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd,
 397     short old, short events, void *p)
 398 {
 399         struct event_change ch;
 400         ch.fd = fd;
 401         ch.old_events = old;
 402         ch.read_change = ch.write_change = ch.close_change = 0;
 403         if (events & EV_WRITE)
 404                 ch.write_change = EV_CHANGE_DEL;
 405         if (events & EV_READ)
 406                 ch.read_change = EV_CHANGE_DEL;
 407         if (events & EV_CLOSED)
 408                 ch.close_change = EV_CHANGE_DEL;
 409
 410         return epoll_apply_one_change(base, base->evbase, &ch);
 411 }
 412
 413 static int
 414 epoll_dispatch(struct event_base *base, struct timeval *tv)
 415 {
 416         struct epollop *epollop = base->evbase;
 417         struct epoll_event *events = epollop->events;
 418         int i, res;
 419         long timeout = -1;
 420
 421 #ifdef USING_TIMERFD
 422         if (epollop->timerfd >= 0) {
 423                 struct itimerspec is;
 424                 is.it_interval.tv_sec = 0;
 425                 is.it_interval.tv_nsec = 0;
 426                 if (tv == NULL) {
 427                         /* No timeout; disarm the timer. */
 428                         is.it_value.tv_sec = 0;
 429                         is.it_value.tv_nsec = 0;
 430                 } else {
 431                         if (tv->tv_sec == 0 && tv->tv_usec == 0) {
 432                                 /* we need to exit immediately; timerfd can't
 433                                  * do that. */
 434                                 timeout = 0;
 435                         }
 436                         is.it_value.tv_sec = tv->tv_sec;
 437                         is.it_value.tv_nsec = tv->tv_usec * 1000;
 438                 }
 439                 /* TODO: we could avoid unnecessary syscalls here by only
 440                    calling timerfd_settime when the top timeout changes, or
 441                    when we're called with a different timeval.
 442                 */
 443                 if (timerfd_settime(epollop->timerfd, 0, &is, NULL) < 0) {
 444                         event_warn("timerfd_settime");
 445                 }
 446         } else
 447 #endif
 448         if (tv != NULL) {
 449                 timeout = evutil_tv_to_msec_(tv);
 450                 if (timeout < 0 || timeout > MAX_EPOLL_TIMEOUT_MSEC) {
 451                         /* Linux kernels can wait forever if the timeout is
 452                          * too big; see comment on MAX_EPOLL_TIMEOUT_MSEC. */
 453                         timeout = MAX_EPOLL_TIMEOUT_MSEC;
 454                 }
 455         }
 456
 457         epoll_apply_changes(base);
 458         event_changelist_remove_all_(&base->changelist, base);
 459
 460         EVBASE_RELEASE_LOCK(base, th_base_lock);
 461
 462         res = epoll_wait(epollop->epfd, events, epollop->nevents, timeout);
 463
 464         EVBASE_ACQUIRE_LOCK(base, th_base_lock);
 465
 466         if (res == -1) {
 467                 if (errno != EINTR) {
 468                         event_warn("epoll_wait");
 469                         return (-1);
 470                 }
 471
 472                 return (0);
 473         }
 474
 475         event_debug(("%s: epoll_wait reports %d", __func__, res));
 476         EVUTIL_ASSERT(res <= epollop->nevents);
 477
 478         for (i = 0; i < res; i++) {
 479                 int what = events[i].events;
 480                 short ev = 0;
 481 #ifdef USING_TIMERFD
 482                 if (events[i].data.fd == epollop->timerfd)
 483                         continue;
 484 #endif
 485
 486                 if (what & (EPOLLHUP|EPOLLERR)) {
 487                         ev = EV_READ | EV_WRITE;
 488                 } else {
 489                         if (what & EPOLLIN)
 490                                 ev |= EV_READ;
 491                         if (what & EPOLLOUT)
 492                                 ev |= EV_WRITE;
 493                         if (what & EPOLLRDHUP)
 494                                 ev |= EV_CLOSED;
 495                 }
 496
 497                 if (!ev)
 498                         continue;
 499
 500                 evmap_io_active_(base, events[i].data.fd, ev | EV_ET);
 501         }
 502
 503         if (res == epollop->nevents && epollop->nevents < MAX_NEVENT) {
 504                 /* We used all of the event space this time.  We should
 505                    be ready for more events next time. */
 506                 int new_nevents = epollop->nevents * 2;
 507                 struct epoll_event *new_events;
 508
 509                 new_events = mm_realloc(epollop->events,
 510                     new_nevents * sizeof(struct epoll_event));
 511                 if (new_events) {
 512                         epollop->events = new_events;
 513                         epollop->nevents = new_nevents;
 514                 }
 515         }
 516
 517         return (0);
 518 }
 519
 520
 521 static void
 522 epoll_dealloc(struct event_base *base)
 523 {
 524         struct epollop *epollop = base->evbase;
 525
 526         evsig_dealloc_(base);
 527         if (epollop->events)
 528                 mm_free(epollop->events);
 529         if (epollop->epfd >= 0)
 530                 close(epollop->epfd);
 531 #ifdef USING_TIMERFD
 532         if (epollop->timerfd >= 0)
 533                 close(epollop->timerfd);
 534 #endif
 535
 536         memset(epollop, 0, sizeof(struct epollop));
 537         mm_free(epollop);
 538 }
 539
 540 #endif /* EVENT__HAVE_EPOLL */