libevent/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 2007-2010 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
  31 #include <sys/types.h>
  32 #ifdef _EVENT_HAVE_SYS_TIME_H
  33 #include <sys/time.h>
  34 #endif
  35 #ifdef _EVENT_HAVE_SYS_SELECT_H
  36 #include <sys/select.h>
  37 #endif
  38 #include <sys/queue.h>
  39 #include <signal.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43 #include <unistd.h>
  44 #include <errno.h>
  45
  46 #include "event-internal.h"
  47 #include "evsignal-internal.h"
  48 #include "event2/thread.h"
  49 #include "evthread-internal.h"
  50 #include "log-internal.h"
  51 #include "evmap-internal.h"
  52
  53 #ifndef howmany
  54 #define howmany(x, y)   (((x)+((y)-1))/(y))
  55 #endif
  56
  57 #ifndef _EVENT_HAVE_FD_MASK
  58 /* This type is mandatory, but Android doesn't define it. */
  59 #undef NFDBITS
  60 #define NFDBITS (sizeof(long)*8)
  61 typedef unsigned long fd_mask;
  62 #endif
  63
  64 struct selectop {
  65         int event_fds;          /* Highest fd in fd set */
  66         int event_fdsz;
  67         int resize_out_sets;
  68         fd_set *event_readset_in;
  69         fd_set *event_writeset_in;
  70         fd_set *event_readset_out;
  71         fd_set *event_writeset_out;
  72 };
  73
  74 static void *select_init(struct event_base *);
  75 static int select_add(struct event_base *, int, short old, short events, void*);
  76 static int select_del(struct event_base *, int, short old, short events, void*);
  77 static int select_dispatch(struct event_base *, struct timeval *);
  78 static void select_dealloc(struct event_base *);
  79
  80 const struct eventop selectops = {
  81         "select",
  82         select_init,
  83         select_add,
  84         select_del,
  85         select_dispatch,
  86         select_dealloc,
  87         0, /* doesn't need reinit. */
  88         EV_FEATURE_FDS,
  89         0,
  90 };
  91
  92 static int select_resize(struct selectop *sop, int fdsz);
  93 static void select_free_selectop(struct selectop *sop);
  94
  95 static void *
  96 select_init(struct event_base *base)
  97 {
  98         struct selectop *sop;
  99
 100         if (!(sop = mm_calloc(1, sizeof(struct selectop))))
 101                 return (NULL);
 102
 103         if (select_resize(sop, howmany(32 + 1, NFDBITS)*sizeof(fd_mask))) {
 104                 select_free_selectop(sop);
 105                 return (NULL);
 106         }
 107
 108         evsig_init(base);
 109
 110         return (sop);
 111 }
 112
 113 #ifdef CHECK_INVARIANTS
 114 static void
 115 check_selectop(struct selectop *sop)
 116 {
 117         /* nothing to be done here */
 118 }
 119 #else
 120 #define check_selectop(sop) do { (void) sop; } while (0)
 121 #endif
 122
 123 static int
 124 select_dispatch(struct event_base *base, struct timeval *tv)
 125 {
 126         int res=0, i, j, nfds;
 127         struct selectop *sop = base->evbase;
 128
 129         check_selectop(sop);
 130         if (sop->resize_out_sets) {
 131                 fd_set *readset_out=NULL, *writeset_out=NULL;
 132                 size_t sz = sop->event_fdsz;
 133                 if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
 134                         return (-1);
 135                 sop->event_readset_out = readset_out;
 136                 if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
 137                         /* We don't free readset_out here, since it was
 138                          * already successfully reallocated. The next time
 139                          * we call select_dispatch, the realloc will be a
 140                          * no-op. */
 141                         return (-1);
 142                 }
 143                 sop->event_writeset_out = writeset_out;
 144                 sop->resize_out_sets = 0;
 145         }
 146
 147         memcpy(sop->event_readset_out, sop->event_readset_in,
 148                sop->event_fdsz);
 149         memcpy(sop->event_writeset_out, sop->event_writeset_in,
 150                sop->event_fdsz);
 151
 152         nfds = sop->event_fds+1;
 153
 154         EVBASE_RELEASE_LOCK(base, th_base_lock);
 155
 156         res = select(nfds, sop->event_readset_out,
 157             sop->event_writeset_out, NULL, tv);
 158
 159         EVBASE_ACQUIRE_LOCK(base, th_base_lock);
 160
 161         check_selectop(sop);
 162
 163         if (res == -1) {
 164                 if (errno != EINTR) {
 165                         event_warn("select");
 166                         return (-1);
 167                 }
 168
 169                 return (0);
 170         }
 171
 172         event_debug(("%s: select reports %d", __func__, res));
 173
 174         check_selectop(sop);
 175         i = random() % nfds;
 176         for (j = 0; j < nfds; ++j) {
 177                 if (++i >= nfds)
 178                         i = 0;
 179                 res = 0;
 180                 if (FD_ISSET(i, sop->event_readset_out))
 181                         res |= EV_READ;
 182                 if (FD_ISSET(i, sop->event_writeset_out))
 183                         res |= EV_WRITE;
 184
 185                 if (res == 0)
 186                         continue;
 187
 188                 evmap_io_active(base, i, res);
 189         }
 190         check_selectop(sop);
 191
 192         return (0);
 193 }
 194
 195 static int
 196 select_resize(struct selectop *sop, int fdsz)
 197 {
 198         fd_set *readset_in = NULL;
 199         fd_set *writeset_in = NULL;
 200
 201         if (sop->event_readset_in)
 202                 check_selectop(sop);
 203
 204         if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
 205                 goto error;
 206         sop->event_readset_in = readset_in;
 207         if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
 208                 /* Note that this will leave event_readset_in expanded.
 209                  * That's okay; we wouldn't want to free it, since that would
 210                  * change the semantics of select_resize from "expand the
 211                  * readset_in and writeset_in, or return -1" to "expand the
 212                  * *set_in members, or trash them and return -1."
 213                  */
 214                 goto error;
 215         }
 216         sop->event_writeset_in = writeset_in;
 217         sop->resize_out_sets = 1;
 218
 219         memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
 220             fdsz - sop->event_fdsz);
 221         memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
 222             fdsz - sop->event_fdsz);
 223
 224         sop->event_fdsz = fdsz;
 225         check_selectop(sop);
 226
 227         return (0);
 228
 229  error:
 230         event_warn("malloc");
 231         return (-1);
 232 }
 233
 234
 235 static int
 236 select_add(struct event_base *base, int fd, short old, short events, void *p)
 237 {
 238         struct selectop *sop = base->evbase;
 239         (void) p;
 240
 241         EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
 242         check_selectop(sop);
 243         /*
 244          * Keep track of the highest fd, so that we can calculate the size
 245          * of the fd_sets for select(2)
 246          */
 247         if (sop->event_fds < fd) {
 248                 int fdsz = sop->event_fdsz;
 249
 250                 if (fdsz < (int)sizeof(fd_mask))
 251                         fdsz = (int)sizeof(fd_mask);
 252
 253                 /* In theory we should worry about overflow here.  In
 254                  * reality, though, the highest fd on a unixy system will
 255                  * not overflow here. XXXX */
 256                 while (fdsz <
 257                     (int) (howmany(fd + 1, NFDBITS) * sizeof(fd_mask)))
 258                         fdsz *= 2;
 259
 260                 if (fdsz != sop->event_fdsz) {
 261                         if (select_resize(sop, fdsz)) {
 262                                 check_selectop(sop);
 263                                 return (-1);
 264                         }
 265                 }
 266
 267                 sop->event_fds = fd;
 268         }
 269
 270         if (events & EV_READ)
 271                 FD_SET(fd, sop->event_readset_in);
 272         if (events & EV_WRITE)
 273                 FD_SET(fd, sop->event_writeset_in);
 274         check_selectop(sop);
 275
 276         return (0);
 277 }
 278
 279 /*
 280  * Nothing to be done here.
 281  */
 282
 283 static int
 284 select_del(struct event_base *base, int fd, short old, short events, void *p)
 285 {
 286         struct selectop *sop = base->evbase;
 287         (void)p;
 288
 289         EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
 290         check_selectop(sop);
 291
 292         if (sop->event_fds < fd) {
 293                 check_selectop(sop);
 294                 return (0);
 295         }
 296
 297         if (events & EV_READ)
 298                 FD_CLR(fd, sop->event_readset_in);
 299
 300         if (events & EV_WRITE)
 301                 FD_CLR(fd, sop->event_writeset_in);
 302
 303         check_selectop(sop);
 304         return (0);
 305 }
 306
 307 static void
 308 select_free_selectop(struct selectop *sop)
 309 {
 310         if (sop->event_readset_in)
 311                 mm_free(sop->event_readset_in);
 312         if (sop->event_writeset_in)
 313                 mm_free(sop->event_writeset_in);
 314         if (sop->event_readset_out)
 315                 mm_free(sop->event_readset_out);
 316         if (sop->event_writeset_out)
 317                 mm_free(sop->event_writeset_out);
 318
 319         memset(sop, 0, sizeof(struct selectop));
 320         mm_free(sop);
 321 }
 322
 323 static void
 324 select_dealloc(struct event_base *base)
 325 {
 326         evsig_dealloc(base);
 327
 328         select_free_selectop(base->evbase);
 329 }