src/select.c

   1 /* select filedescriptor handling, taken from:
   2  * userspace logging daemon for the iptables ULOG target
   3  * of the linux 2.4 netfilter subsystem.
   4  *
   5  * (C) 2000-2009 by Harald Welte <laforge@gnumonks.org>
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2 of the License, or
  10  *  (at your option) any later version.
  11  *
  12  *  This program is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with this program; if not, write to the Free Software
  19  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <fcntl.h>
  23 #include <stdio.h>
  24
  25 #include <osmocom/core/select.h>
  26 #include <osmocom/core/linuxlist.h>
  27 #include <osmocom/core/timer.h>
  28
  29 #include "../config.h"
  30
  31 #ifdef HAVE_SYS_SELECT_H
  32
  33 /*! \addtogroup select
  34  *  @{
  35  */
  36
  37 /*! \file select.c
  38  *  \brief select loop abstraction
  39  */
  40
  41 static int maxfd = 0;
  42 static LLIST_HEAD(osmo_fds);
  43 static int unregistered_count;
  44
  45 /*! \brief Register a new file descriptor with select loop abstraction
  46  *  \param[in] fd osmocom file descriptor to be registered
  47  */
  48 int osmo_fd_register(struct osmo_fd *fd)
  49 {
  50         int flags;
  51
  52         /* make FD nonblocking */
  53         flags = fcntl(fd->fd, F_GETFL);
  54         if (flags < 0)
  55                 return flags;
  56         flags |= O_NONBLOCK;
  57         flags = fcntl(fd->fd, F_SETFL, flags);
  58         if (flags < 0)
  59                 return flags;
  60
  61         /* set close-on-exec flag */
  62         flags = fcntl(fd->fd, F_GETFD);
  63         if (flags < 0)
  64                 return flags;
  65         flags |= FD_CLOEXEC;
  66         flags = fcntl(fd->fd, F_SETFD, flags);
  67         if (flags < 0)
  68                 return flags;
  69
  70         /* Register FD */
  71         if (fd->fd > maxfd)
  72                 maxfd = fd->fd;
  73
  74 #ifdef BSC_FD_CHECK
  75         struct osmo_fd *entry;
  76         llist_for_each_entry(entry, &osmo_fds, list) {
  77                 if (entry == fd) {
  78                         fprintf(stderr, "Adding a osmo_fd that is already in the list.\n");
  79                         return 0;
  80                 }
  81         }
  82 #endif
  83
  84         llist_add_tail(&fd->list, &osmo_fds);
  85
  86         return 0;
  87 }
  88
  89 /*! \brief Unregister a file descriptor from select loop abstraction
  90  *  \param[in] fd osmocom file descriptor to be unregistered
  91  */
  92 void osmo_fd_unregister(struct osmo_fd *fd)
  93 {
  94         unregistered_count++;
  95         llist_del(&fd->list);
  96 }
  97
  98 /*! \brief select main loop integration
  99  *  \param[in] polling should we pollonly (1) or block on select (0)
 100  */
 101 int osmo_select_main(int polling)
 102 {
 103         struct osmo_fd *ufd, *tmp;
 104         fd_set readset, writeset, exceptset;
 105         int work = 0, rc;
 106         struct timeval no_time = {0, 0};
 107
 108         FD_ZERO(&readset);
 109         FD_ZERO(&writeset);
 110         FD_ZERO(&exceptset);
 111
 112         /* prepare read and write fdsets */
 113         llist_for_each_entry(ufd, &osmo_fds, list) {
 114                 if (ufd->when & BSC_FD_READ)
 115                         FD_SET(ufd->fd, &readset);
 116
 117                 if (ufd->when & BSC_FD_WRITE)
 118                         FD_SET(ufd->fd, &writeset);
 119
 120                 if (ufd->when & BSC_FD_EXCEPT)
 121                         FD_SET(ufd->fd, &exceptset);
 122         }
 123
 124         osmo_timers_check();
 125
 126         if (!polling)
 127                 osmo_timers_prepare();
 128         rc = select(maxfd+1, &readset, &writeset, &exceptset, polling ? &no_time : osmo_timers_nearest());
 129         if (rc < 0)
 130                 return 0;
 131
 132         /* fire timers */
 133         osmo_timers_update();
 134
 135         /* call registered callback functions */
 136 restart:
 137         unregistered_count = 0;
 138         llist_for_each_entry_safe(ufd, tmp, &osmo_fds, list) {
 139                 int flags = 0;
 140
 141                 if (FD_ISSET(ufd->fd, &readset)) {
 142                         flags |= BSC_FD_READ;
 143                         FD_CLR(ufd->fd, &readset);
 144                 }
 145
 146                 if (FD_ISSET(ufd->fd, &writeset)) {
 147                         flags |= BSC_FD_WRITE;
 148                         FD_CLR(ufd->fd, &writeset);
 149                 }
 150
 151                 if (FD_ISSET(ufd->fd, &exceptset)) {
 152                         flags |= BSC_FD_EXCEPT;
 153                         FD_CLR(ufd->fd, &exceptset);
 154                 }
 155
 156                 if (flags) {
 157                         work = 1;
 158                         ufd->cb(ufd, flags);
 159                 }
 160                 /* ugly, ugly hack. If more than one filedescriptors were
 161                  * unregistered, they might have been consecutive and
 162                  * llist_for_each_entry_safe() is no longer safe */
 163                 /* this seems to happen with the last element of the list as well */
 164                 if (unregistered_count >= 1)
 165                         goto restart;
 166         }
 167         return work;
 168 }
 169
 170 /*! }@ */
 171
 172 #endif /* _HAVE_SYS_SELECT_H */