sysdeps/unix/sysv/linux/poll.c

   1 /* Poll system call, with emulation if it is not available.
   2    Copyright (C) 1997,1998,1999,2000,2001,2002,2006
   3         Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <errno.h>
  22 #include <sys/poll.h>
  23
  24 #include <sysdep-cancel.h>
  25 #include <sys/syscall.h>
  26 #include <bp-checks.h>
  27
  28 #include <kernel-features.h>
  29
  30 #if defined __NR_poll || __ASSUME_POLL_SYSCALL > 0
  31
  32 # if __ASSUME_POLL_SYSCALL == 0
  33 static int __emulate_poll (struct pollfd *fds, nfds_t nfds,
  34                            int timeout) internal_function;
  35 # endif
  36
  37
  38 # if __ASSUME_POLL_SYSCALL == 0
  39 /* For loser kernels.  */
  40 static int
  41 loser_poll (struct pollfd *fds, nfds_t nfds, int timeout)
  42 {
  43   static int must_emulate;
  44
  45   if (!must_emulate)
  46     {
  47       int errno_saved = errno;
  48       int retval = INLINE_SYSCALL (poll, 3, CHECK_N (fds, nfds), nfds,
  49                                    timeout);
  50
  51       if (retval >= 0 || errno != ENOSYS)
  52         return retval;
  53
  54       __set_errno (errno_saved);
  55       must_emulate = 1;
  56     }
  57
  58   return __emulate_poll (fds, nfds, timeout);
  59 }
  60 # endif
  61
  62
  63 /* The real implementation.  */
  64 int
  65 __poll (fds, nfds, timeout)
  66      struct pollfd *fds;
  67      nfds_t nfds;
  68      int timeout;
  69 {
  70 # if __ASSUME_POLL_SYSCALL == 0
  71   if (SINGLE_THREAD_P)
  72     return loser_poll (CHECK_N (fds, nfds), nfds, timeout);
  73
  74   int oldtype = LIBC_CANCEL_ASYNC ();
  75
  76   int result = loser_poll (CHECK_N (fds, nfds), nfds, timeout);
  77
  78    LIBC_CANCEL_RESET (oldtype);
  79
  80   return result;
  81 # else
  82   if (SINGLE_THREAD_P)
  83     return INLINE_SYSCALL (poll, 3, CHECK_N (fds, nfds), nfds, timeout);
  84
  85   int oldtype = LIBC_CANCEL_ASYNC ();
  86
  87   int result = INLINE_SYSCALL (poll, 3, CHECK_N (fds, nfds), nfds, timeout);
  88
  89    LIBC_CANCEL_RESET (oldtype);
  90
  91   return result;
  92 # endif
  93 }
  94 libc_hidden_def (__poll)
  95 weak_alias (__poll, poll)
  96 strong_alias (__poll, __libc_poll)
  97
  98 /* Get the emulation code.  */
  99 # define __poll(fds, nfds, timeout) \
 100   static internal_function __emulate_poll (fds, nfds, timeout)
 101 #endif
 102
 103 #if __ASSUME_POLL_SYSCALL == 0
 104 # include <sysdeps/unix/bsd/poll.c>
 105 #endif