usr.bin/doscmd/AsyncIO.c

   1 /*
   2  * Copyright (c) 1992, 1993, 1996
   3  *      Berkeley Software Design, Inc.  All rights reserved.
   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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by Berkeley Software
  16  *      Design, Inc.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  *      BSDI AsyncIO.c,v 2.2 1996/04/08 19:32:10 bostic Exp
  31  *
  32  * $FreeBSD: src/usr.bin/doscmd/AsyncIO.c,v 1.3.2.3 2002/05/21 11:49:47 tg Exp $
  33  * $DragonFly: src/usr.bin/doscmd/AsyncIO.c,v 1.3 2008/10/16 01:52:32 swildner Exp $
  34  */
  35
  36 #include <sys/param.h>
  37 #include <sys/types.h>
  38 #include <sys/time.h>
  39 #include <errno.h>
  40 #include <fcntl.h>
  41 #include <limits.h>
  42 #include <signal.h>
  43 #include <stdio.h>
  44 #include <unistd.h>
  45
  46 #include "doscmd.h"
  47 #include "AsyncIO.h"
  48
  49 #define FD_ISZERO(p)    ((p)->fds_bits[0] == 0)
  50
  51 /*
  52  * Set or Clear the Async nature of an FD
  53  */
  54
  55 #define SETASYNC(fd)    fcntl(fd, F_SETFL, handlers[fd].flag | FASYNC)
  56 #define CLRASYNC(fd)    fcntl(fd, F_SETFL, handlers[fd].flag & ~FASYNC)
  57
  58 /*
  59  * Request that ``func'' be called everytime data is available on ``fd''
  60  */
  61
  62 static  fd_set  fdset;          /* File Descriptors to select on */
  63
  64 typedef struct {
  65         void    (*func)(int, int, void *, regcontext_t *);
  66                                         /* Function to call on data arrival */
  67         void    (*failure)(void *);     /* Function to call on failure */
  68         void    *arg;                   /* Argument to above functions */
  69         int     lockcnt;                /* Nested level of lock */
  70         fd_set  members;                /* Set of FD's to disable on SIGIO */
  71         int     flag;                   /* The flag from F_GETFL (we own it) */
  72 } Async;
  73
  74 static Async    handlers[OPEN_MAX];
  75
  76 static void     CleanIO(void);
  77 static void     HandleIO(struct sigframe *sf);
  78
  79 void
  80 _RegisterIO(int fd, void (*func)(int, int, void *, regcontext_t *),
  81     void *arg, void (*failure)(void *))
  82 {
  83         static int firsttime = 1;
  84         Async *as;
  85
  86         if (fd < 0 || fd > OPEN_MAX) {
  87 printf("%d: Invalid FD\n", fd);
  88                 return;
  89         }
  90
  91         as = &handlers[fd];
  92
  93         if ((as->flag = fcntl(fd, F_GETFL, 0)) == -1) {
  94                 if (func) {
  95 /*@*/                   perror("get fcntl");
  96 /*@*/                   abort();
  97                         return;
  98                 }
  99         }
 100
 101         if (firsttime) {
 102                 firsttime = 0;
 103                 setsignal(SIGIO, HandleIO);
 104         }
 105
 106         if ((handlers[fd].func = func) != 0) {
 107                 as->lockcnt = 0;
 108                 as->arg = arg;
 109                 as->failure = failure;
 110
 111                 FD_SET(fd, &fdset);
 112                 FD_ZERO(&handlers[fd].members);
 113                 FD_SET(fd, &handlers[fd].members);
 114                 if (fcntl(fd, F_SETOWN, getpid()) < 0) {
 115 /*@*/                   perror("SETOWN");
 116                 }
 117                 SETASYNC(fd);
 118         } else {
 119                 as->arg = 0;
 120                 as->failure = 0;
 121                 as->lockcnt = 0;
 122
 123                 CLRASYNC(fd);
 124                 FD_CLR(fd, &fdset);
 125         }
 126 }
 127
 128 static void
 129 CleanIO(void)
 130 {
 131         int x;
 132         static struct timeval tv;
 133
 134         /*
 135          * For every file des in fd_set, we check to see if it
 136          * causes a fault on select().  If so, we unregister it
 137          * for the user.
 138          */
 139         for (x = 0; x < OPEN_MAX; ++x) {
 140                 fd_set set;
 141
 142                 if (!FD_ISSET(x, &fdset))
 143                         continue;
 144
 145                 FD_ZERO(&set);
 146                 FD_SET(x, &set);
 147                 errno = 0;
 148                 if (select(FD_SETSIZE, &set, 0, 0, &tv) < 0 &&
 149                     errno == EBADF) {
 150                         void (*f)(void *);
 151                         void *a;
 152 printf("Closed file descriptor %d\n", x);
 153
 154                         f = handlers[x].failure;
 155                         a = handlers[x].arg;
 156                         handlers[x].failure = 0;
 157                         handlers[x].func = 0;
 158                         handlers[x].arg = 0;
 159                         handlers[x].lockcnt = 0;
 160                         FD_CLR(x, &fdset);
 161                         if (f)
 162                                 (*f)(a);
 163                 }
 164         }
 165 }
 166
 167 static void
 168 HandleIO(struct sigframe *sf)
 169 {
 170         static struct timeval tv;
 171         fd_set readset, writeset;
 172         int x, fd;
 173
 174 again:
 175         readset = writeset = fdset;
 176         if ((x = select(FD_SETSIZE, &readset, &writeset, 0, &tv)) < 0) {
 177                 /*
 178                  * If we failed because of a BADFiledes, go find
 179                  * which one(s), fail them out and then try a
 180                  * new select to see if any of the good ones are
 181                  * okay.
 182                  */
 183                 if (errno == EBADF) {
 184                         CleanIO();
 185                         if (FD_ISZERO(&fdset))
 186                                 return;
 187                         goto again;
 188                 }
 189                 perror("select");
 190                 return;
 191         }
 192
 193         /*
 194          * If we run out of fds to look at, break out of the loop
 195          * and exit the handler.
 196          */
 197         if (x == 0)
 198                 return;
 199
 200         /*
 201          * If there is at least 1 fd saying it has something for
 202          * us, then loop through the sets looking for those
 203          * bits, stopping when we have handleed the number it has
 204          * asked for.
 205          */
 206         for (fd = 0; x && fd < OPEN_MAX; fd ++) {
 207                 Async *as;
 208                 int cond;
 209
 210                 cond = 0;
 211
 212                 if (FD_ISSET(fd, &readset)) {
 213                         cond |= AS_RD;
 214                         x --;
 215                 }
 216                 if (FD_ISSET(fd, &writeset)) {
 217                         cond |= AS_WR;
 218                         x --;
 219                 }
 220
 221                 if (cond == 0)
 222                         continue;
 223
 224                 /*
 225                  * Is suppose it is possible that one of the previous
 226                  * I/O requests changed the fdset.
 227                  * We do know that SIGIO is turned off right now,
 228                  * so it is safe to checkit.
 229                  */
 230                 if (!FD_ISSET(fd, &fdset)) {
 231                         continue;
 232                 }
 233                 as = &handlers[fd];
 234
 235                 /*
 236                  * as in above, maybe someone locked us...
 237                  * we are in dangerous water now if we are
 238                  * multi-tasked
 239                  */
 240                 if (as->lockcnt) {
 241                         fprintf(stderr, "Selected IO on locked %d\n",fd);
 242                         continue;
 243                 }
 244                 /*
 245                  * Okay, now if there exists a handler, we should
 246                  * call it.  We must turn back on SIGIO if there
 247                  * are possibly other people waiting for it.
 248                  */
 249                 if (as->func) {
 250                         (*handlers[fd].func)(fd, cond, handlers[fd].arg,
 251                             (regcontext_t *)&sf->sf_uc.uc_mcontext);
 252                 } else {
 253                         /*
 254                          * Otherwise deregister this guy.
 255                          */
 256                         _RegisterIO(fd, 0, 0, 0);
 257                 }
 258         }
 259         /*
 260          * If we did not process all the fd's, then we should
 261          * break out of the probable infinite loop.
 262          */
 263 }