granicus.if.org Git - libevent/blob - select.c

   1 /*      $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $       */
   2
   3 /*
   4  * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
   5  * Copyright 2007-2012 Niels Provos and Nick Mathewson
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. The name of the author may not be used to endorse or promote products
  16  *    derived from this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29 #include "event2/event-config.h"
  30 #include "evconfig-private.h"
  31
  32 #ifdef EVENT__HAVE_SELECT
  33
  34 #ifdef __APPLE__
  35 /* Apple wants us to define this if we might ever pass more than
  36  * FD_SETSIZE bits to select(). */
  37 #define _DARWIN_UNLIMITED_SELECT
  38 #endif
  39
  40 #include <sys/types.h>
  41 #ifdef EVENT__HAVE_SYS_TIME_H
  42 #include <sys/time.h>
  43 #endif
  44 #ifdef EVENT__HAVE_SYS_SELECT_H
  45 #include <sys/select.h>
  46 #endif
  47 #include <sys/queue.h>
  48 #include <signal.h>
  49 #include <stdio.h>
  50 #include <stdlib.h>
  51 #include <string.h>
  52 #include <unistd.h>
  53 #include <errno.h>
  54
  55 #include "event-internal.h"
  56 #include "evsignal-internal.h"
  57 #include "event2/thread.h"
  58 #include "evthread-internal.h"
  59 #include "log-internal.h"
  60 #include "evmap-internal.h"
  61
  62 #ifndef EVENT__HAVE_FD_MASK
  63 /* This type is mandatory, but Android doesn't define it. */
  64 typedef unsigned long fd_mask;
  65 #endif
  66
  67 #ifndef NFDBITS
  68 #define NFDBITS (sizeof(fd_mask)*8)
  69 #endif
  70
  71 /* Divide positive x by y, rounding up. */
  72 #define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))
  73
  74 /* How many bytes to allocate for N fds? */
  75 #define SELECT_ALLOC_SIZE(n) \
  76         (DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))
  77
  78 struct selectop {
  79         int event_fds;          /* Highest fd in fd set */
  80         int event_fdsz;
  81         int resize_out_sets;
  82         fd_set *event_readset_in;
  83         fd_set *event_writeset_in;
  84         fd_set *event_readset_out;
  85         fd_set *event_writeset_out;
  86 };
  87
  88 static void *select_init(struct event_base *);
  89 static int select_add(struct event_base *, int, short old, short events, void*);
  90 static int select_del(struct event_base *, int, short old, short events, void*);
  91 static int select_dispatch(struct event_base *, struct timeval *);
  92 static void select_dealloc(struct event_base *);
  93
  94 const struct eventop selectops = {
  95         "select",
  96         select_init,
  97         select_add,
  98         select_del,
  99         select_dispatch,
 100         select_dealloc,
 101         1, /* need_reinit. */
 102         EV_FEATURE_FDS,
 103         0,
 104 };
 105
 106 static int select_resize(struct selectop *sop, int fdsz);
 107 static void select_free_selectop(struct selectop *sop);
 108
 109 static void *
 110 select_init(struct event_base *base)
 111 {
 112         struct selectop *sop;
 113
 114         if (!(sop = mm_calloc(1, sizeof(struct selectop))))
 115                 return (NULL);
 116
 117         if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {
 118                 select_free_selectop(sop);
 119                 return (NULL);
 120         }
 121
 122         if (sigfd_init_(base) < 0)
 123                 evsig_init_(base);
 124
 125         evutil_weakrand_seed_(&base->weakrand_seed, 0);
 126
 127         return (sop);
 128 }
 129
 130 #ifdef CHECK_INVARIANTS
 131 static void
 132 check_selectop(struct selectop *sop)
 133 {
 134         /* nothing to be done here */
 135 }
 136 #else
 137 #define check_selectop(sop) do { (void) sop; } while (0)
 138 #endif
 139
 140 static int
 141 select_dispatch(struct event_base *base, struct timeval *tv)
 142 {
 143         int res=0, i, j, nfds;
 144         struct selectop *sop = base->evbase;
 145
 146         check_selectop(sop);
 147         if (sop->resize_out_sets) {
 148                 fd_set *readset_out=NULL, *writeset_out=NULL;
 149                 size_t sz = sop->event_fdsz;
 150                 if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
 151                         return (-1);
 152                 sop->event_readset_out = readset_out;
 153                 if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
 154                         /* We don't free readset_out here, since it was
 155                          * already successfully reallocated. The next time
 156                          * we call select_dispatch, the realloc will be a
 157                          * no-op. */
 158                         return (-1);
 159                 }
 160                 sop->event_writeset_out = writeset_out;
 161                 sop->resize_out_sets = 0;
 162         }
 163
 164         memcpy(sop->event_readset_out, sop->event_readset_in,
 165                sop->event_fdsz);
 166         memcpy(sop->event_writeset_out, sop->event_writeset_in,
 167                sop->event_fdsz);
 168
 169         nfds = sop->event_fds+1;
 170
 171         EVBASE_RELEASE_LOCK(base, th_base_lock);
 172
 173         res = select(nfds, sop->event_readset_out,
 174             sop->event_writeset_out, NULL, tv);
 175
 176         EVBASE_ACQUIRE_LOCK(base, th_base_lock);
 177
 178         check_selectop(sop);
 179
 180         if (res == -1) {
 181                 if (errno != EINTR) {
 182                         event_warn("select");
 183                         return (-1);
 184                 }
 185
 186                 return (0);
 187         }
 188
 189         event_debug(("%s: select reports %d", __func__, res));
 190
 191         check_selectop(sop);
 192         i = evutil_weakrand_range_(&base->weakrand_seed, nfds);
 193         for (j = 0; j < nfds; ++j) {
 194                 if (++i >= nfds)
 195                         i = 0;
 196                 res = 0;
 197                 if (FD_ISSET(i, sop->event_readset_out))
 198                         res |= EV_READ;
 199                 if (FD_ISSET(i, sop->event_writeset_out))
 200                         res |= EV_WRITE;
 201
 202                 if (res == 0)
 203                         continue;
 204
 205                 evmap_io_active_(base, i, res);
 206         }
 207         check_selectop(sop);
 208
 209         return (0);
 210 }
 211
 212 static int
 213 select_resize(struct selectop *sop, int fdsz)
 214 {
 215         fd_set *readset_in = NULL;
 216         fd_set *writeset_in = NULL;
 217
 218         if (sop->event_readset_in)
 219                 check_selectop(sop);
 220
 221         if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
 222                 goto error;
 223         sop->event_readset_in = readset_in;
 224         if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
 225                 /* Note that this will leave event_readset_in expanded.
 226                  * That's okay; we wouldn't want to free it, since that would
 227                  * change the semantics of select_resize from "expand the
 228                  * readset_in and writeset_in, or return -1" to "expand the
 229                  * *set_in members, or trash them and return -1."
 230                  */
 231                 goto error;
 232         }
 233         sop->event_writeset_in = writeset_in;
 234         sop->resize_out_sets = 1;
 235
 236         memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
 237             fdsz - sop->event_fdsz);
 238         memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
 239             fdsz - sop->event_fdsz);
 240
 241         sop->event_fdsz = fdsz;
 242         check_selectop(sop);
 243
 244         return (0);
 245
 246  error:
 247         event_warn("malloc");
 248         return (-1);
 249 }
 250
 251
 252 static int
 253 select_add(struct event_base *base, int fd, short old, short events, void *p)
 254 {
 255         struct selectop *sop = base->evbase;
 256         (void) p;
 257
 258         EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
 259         check_selectop(sop);
 260         /*
 261          * Keep track of the highest fd, so that we can calculate the size
 262          * of the fd_sets for select(2)
 263          */
 264         if (sop->event_fds < fd) {
 265                 int fdsz = sop->event_fdsz;
 266
 267                 if (fdsz < (int)sizeof(fd_mask))
 268                         fdsz = (int)sizeof(fd_mask);
 269
 270                 /* In theory we should worry about overflow here.  In
 271                  * reality, though, the highest fd on a unixy system will
 272                  * not overflow here. XXXX */
 273                 while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))
 274                         fdsz *= 2;
 275
 276                 if (fdsz != sop->event_fdsz) {
 277                         if (select_resize(sop, fdsz)) {
 278                                 check_selectop(sop);
 279                                 return (-1);
 280                         }
 281                 }
 282
 283                 sop->event_fds = fd;
 284         }
 285
 286         if (events & EV_READ)
 287                 FD_SET(fd, sop->event_readset_in);
 288         if (events & EV_WRITE)
 289                 FD_SET(fd, sop->event_writeset_in);
 290         check_selectop(sop);
 291
 292         return (0);
 293 }
 294
 295 /*
 296  * Nothing to be done here.
 297  */
 298
 299 static int
 300 select_del(struct event_base *base, int fd, short old, short events, void *p)
 301 {
 302         struct selectop *sop = base->evbase;
 303         (void)p;
 304
 305         EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
 306         check_selectop(sop);
 307
 308         if (sop->event_fds < fd) {
 309                 check_selectop(sop);
 310                 return (0);
 311         }
 312
 313         if (events & EV_READ)
 314                 FD_CLR(fd, sop->event_readset_in);
 315
 316         if (events & EV_WRITE)
 317                 FD_CLR(fd, sop->event_writeset_in);
 318
 319         check_selectop(sop);
 320         return (0);
 321 }
 322
 323 static void
 324 select_free_selectop(struct selectop *sop)
 325 {
 326         if (sop->event_readset_in)
 327                 mm_free(sop->event_readset_in);
 328         if (sop->event_writeset_in)
 329                 mm_free(sop->event_writeset_in);
 330         if (sop->event_readset_out)
 331                 mm_free(sop->event_readset_out);
 332         if (sop->event_writeset_out)
 333                 mm_free(sop->event_writeset_out);
 334
 335         memset(sop, 0, sizeof(struct selectop));
 336         mm_free(sop);
 337 }
 338
 339 static void
 340 select_dealloc(struct event_base *base)
 341 {
 342         evsig_dealloc_(base);
 343
 344         select_free_selectop(base->evbase);
 345 }
 346
 347 #endif /* EVENT__HAVE_SELECT */