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 2007-2012 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
  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 _EVENT_HAVE_FD_MASK
  54 /* This type is mandatory, but Android doesn't define it. */
  55 typedef unsigned long fd_mask;
  56 #endif
  57
  58 #ifndef NFDBITS
  59 #define NFDBITS (sizeof(fd_mask)*8)
  60 #endif
  61
  62 /* Divide positive x by y, rounding up. */
  63 #define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))
  64
  65 /* How many bytes to allocate for N fds? */
  66 #define SELECT_ALLOC_SIZE(n) \
  67         (DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))
  68
  69 struct selectop {
  70         int event_fds;          /* Highest fd in fd set */
  71         int event_fdsz;
  72         int resize_out_sets;
  73         fd_set *event_readset_in;
  74         fd_set *event_writeset_in;
  75         fd_set *event_readset_out;
  76         fd_set *event_writeset_out;
  77 };
  78
  79 static void *select_init(struct event_base *);
  80 static int select_add(struct event_base *, int, short old, short events, void*);
  81 static int select_del(struct event_base *, int, short old, short events, void*);
  82 static int select_dispatch(struct event_base *, struct timeval *);
  83 static void select_dealloc(struct event_base *);
  84
  85 const struct eventop selectops = {
  86         "select",
  87         select_init,
  88         select_add,
  89         select_del,
  90         select_dispatch,
  91         select_dealloc,
  92         0, /* doesn't need reinit. */
  93         EV_FEATURE_FDS,
  94         0,
  95 };
  96
  97 static int select_resize(struct selectop *sop, int fdsz);
  98 static void select_free_selectop(struct selectop *sop);
  99
 100 static void *
 101 select_init(struct event_base *base)
 102 {
 103         struct selectop *sop;
 104
 105         if (!(sop = mm_calloc(1, sizeof(struct selectop))))
 106                 return (NULL);
 107
 108         if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {
 109                 select_free_selectop(sop);
 110                 return (NULL);
 111         }
 112
 113         evsig_init(base);
 114
 115         return (sop);
 116 }
 117
 118 #ifdef CHECK_INVARIANTS
 119 static void
 120 check_selectop(struct selectop *sop)
 121 {
 122         /* nothing to be done here */
 123 }
 124 #else
 125 #define check_selectop(sop) do { (void) sop; } while (0)
 126 #endif
 127
 128 static int
 129 select_dispatch(struct event_base *base, struct timeval *tv)
 130 {
 131         int res=0, i, j, nfds;
 132         struct selectop *sop = base->evbase;
 133
 134         check_selectop(sop);
 135         if (sop->resize_out_sets) {
 136                 fd_set *readset_out=NULL, *writeset_out=NULL;
 137                 size_t sz = sop->event_fdsz;
 138                 if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
 139                         return (-1);
 140                 sop->event_readset_out = readset_out;
 141                 if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
 142                         /* We don't free readset_out here, since it was
 143                          * already successfully reallocated. The next time
 144                          * we call select_dispatch, the realloc will be a
 145                          * no-op. */
 146                         return (-1);
 147                 }
 148                 sop->event_writeset_out = writeset_out;
 149                 sop->resize_out_sets = 0;
 150         }
 151
 152         memcpy(sop->event_readset_out, sop->event_readset_in,
 153                sop->event_fdsz);
 154         memcpy(sop->event_writeset_out, sop->event_writeset_in,
 155                sop->event_fdsz);
 156
 157         nfds = sop->event_fds+1;
 158
 159         EVBASE_RELEASE_LOCK(base, th_base_lock);
 160
 161         res = select(nfds, sop->event_readset_out,
 162             sop->event_writeset_out, NULL, tv);
 163
 164         EVBASE_ACQUIRE_LOCK(base, th_base_lock);
 165
 166         check_selectop(sop);
 167
 168         if (res == -1) {
 169                 if (errno != EINTR) {
 170                         event_warn("select");
 171                         return (-1);
 172                 }
 173
 174                 return (0);
 175         }
 176
 177         event_debug(("%s: select reports %d", __func__, res));
 178
 179         check_selectop(sop);
 180         i = random() % nfds;
 181         for (j = 0; j < nfds; ++j) {
 182                 if (++i >= nfds)
 183                         i = 0;
 184                 res = 0;
 185                 if (FD_ISSET(i, sop->event_readset_out))
 186                         res |= EV_READ;
 187                 if (FD_ISSET(i, sop->event_writeset_out))
 188                         res |= EV_WRITE;
 189
 190                 if (res == 0)
 191                         continue;
 192
 193                 evmap_io_active(base, i, res);
 194         }
 195         check_selectop(sop);
 196
 197         return (0);
 198 }
 199
 200 static int
 201 select_resize(struct selectop *sop, int fdsz)
 202 {
 203         fd_set *readset_in = NULL;
 204         fd_set *writeset_in = NULL;
 205
 206         if (sop->event_readset_in)
 207                 check_selectop(sop);
 208
 209         if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
 210                 goto error;
 211         sop->event_readset_in = readset_in;
 212         if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
 213                 /* Note that this will leave event_readset_in expanded.
 214                  * That's okay; we wouldn't want to free it, since that would
 215                  * change the semantics of select_resize from "expand the
 216                  * readset_in and writeset_in, or return -1" to "expand the
 217                  * *set_in members, or trash them and return -1."
 218                  */
 219                 goto error;
 220         }
 221         sop->event_writeset_in = writeset_in;
 222         sop->resize_out_sets = 1;
 223
 224         memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
 225             fdsz - sop->event_fdsz);
 226         memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
 227             fdsz - sop->event_fdsz);
 228
 229         sop->event_fdsz = fdsz;
 230         check_selectop(sop);
 231
 232         return (0);
 233
 234  error:
 235         event_warn("malloc");
 236         return (-1);
 237 }
 238
 239
 240 static int
 241 select_add(struct event_base *base, int fd, short old, short events, void *p)
 242 {
 243         struct selectop *sop = base->evbase;
 244         (void) p;
 245
 246         EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
 247         check_selectop(sop);
 248         /*
 249          * Keep track of the highest fd, so that we can calculate the size
 250          * of the fd_sets for select(2)
 251          */
 252         if (sop->event_fds < fd) {
 253                 int fdsz = sop->event_fdsz;
 254
 255                 if (fdsz < (int)sizeof(fd_mask))
 256                         fdsz = (int)sizeof(fd_mask);
 257
 258                 /* In theory we should worry about overflow here.  In
 259                  * reality, though, the highest fd on a unixy system will
 260                  * not overflow here. XXXX */
 261                 while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))
 262                         fdsz *= 2;
 263
 264                 if (fdsz != sop->event_fdsz) {
 265                         if (select_resize(sop, fdsz)) {
 266                                 check_selectop(sop);
 267                                 return (-1);
 268                         }
 269                 }
 270
 271                 sop->event_fds = fd;
 272         }
 273
 274         if (events & EV_READ)
 275                 FD_SET(fd, sop->event_readset_in);
 276         if (events & EV_WRITE)
 277                 FD_SET(fd, sop->event_writeset_in);
 278         check_selectop(sop);
 279
 280         return (0);
 281 }
 282
 283 /*
 284  * Nothing to be done here.
 285  */
 286
 287 static int
 288 select_del(struct event_base *base, int fd, short old, short events, void *p)
 289 {
 290         struct selectop *sop = base->evbase;
 291         (void)p;
 292
 293         EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
 294         check_selectop(sop);
 295
 296         if (sop->event_fds < fd) {
 297                 check_selectop(sop);
 298                 return (0);
 299         }
 300
 301         if (events & EV_READ)
 302                 FD_CLR(fd, sop->event_readset_in);
 303
 304         if (events & EV_WRITE)
 305                 FD_CLR(fd, sop->event_writeset_in);
 306
 307         check_selectop(sop);
 308         return (0);
 309 }
 310
 311 static void
 312 select_free_selectop(struct selectop *sop)
 313 {
 314         if (sop->event_readset_in)
 315                 mm_free(sop->event_readset_in);
 316         if (sop->event_writeset_in)
 317                 mm_free(sop->event_writeset_in);
 318         if (sop->event_readset_out)
 319                 mm_free(sop->event_readset_out);
 320         if (sop->event_writeset_out)
 321                 mm_free(sop->event_writeset_out);
 322
 323         memset(sop, 0, sizeof(struct selectop));
 324         mm_free(sop);
 325 }
 326
 327 static void
 328 select_dealloc(struct event_base *base)
 329 {
 330         evsig_dealloc(base);
 331
 332         select_free_selectop(base->evbase);
 333 }