| 1 | /*
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| 2 | Unix SMB/Netbios implementation.
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| 3 | Version 3.0
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| 4 | Samba select/poll implementation
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| 5 | Copyright (C) Andrew Tridgell 1992-1998
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| 6 |
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| 7 | This program is free software; you can redistribute it and/or modify
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| 8 | it under the terms of the GNU General Public License as published by
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| 9 | the Free Software Foundation; either version 3 of the License, or
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| 10 | (at your option) any later version.
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| 11 |
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| 12 | This program is distributed in the hope that it will be useful,
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| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 15 | GNU General Public License for more details.
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| 16 |
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| 17 | You should have received a copy of the GNU General Public License
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| 18 | along with this program. If not, see <http://www.gnu.org/licenses/>.
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| 19 | */
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| 20 |
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| 21 | #include "includes.h"
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| 22 |
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| 23 | /* This is here because it allows us to avoid a nasty race in signal handling.
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| 24 | We need to guarantee that when we get a signal we get out of a select immediately
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| 25 | but doing that involves a race condition. We can avoid the race by getting the
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| 26 | signal handler to write to a pipe that is in the select/poll list
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| 27 |
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| 28 | This means all Samba signal handlers should call sys_select_signal().
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| 29 | */
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| 30 |
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| 31 | static pid_t initialised;
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| 32 | static int select_pipe[2];
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| 33 | static volatile unsigned pipe_written, pipe_read;
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| 34 |
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| 35 | /*******************************************************************
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| 36 | Call this from all Samba signal handlers if you want to avoid a
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| 37 | nasty signal race condition.
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| 38 | ********************************************************************/
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| 39 |
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| 40 | void sys_select_signal(char c)
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| 41 | {
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| 42 | int saved_errno = errno;
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| 43 |
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| 44 | if (!initialised) return;
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| 45 |
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| 46 | if (pipe_written > pipe_read+256) return;
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| 47 |
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| 48 | if (write(select_pipe[1], &c, 1) == 1) pipe_written++;
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| 49 |
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| 50 | errno = saved_errno;
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| 51 | }
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| 52 |
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| 53 | /*******************************************************************
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| 54 | Like select() but avoids the signal race using a pipe
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| 55 | it also guuarantees that fds on return only ever contains bits set
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| 56 | for file descriptors that were readable.
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| 57 | ********************************************************************/
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| 58 |
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| 59 | int sys_select(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
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| 60 | {
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| 61 | int ret, saved_errno;
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| 62 | fd_set *readfds2, readfds_buf;
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| 63 |
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| 64 | if (initialised != sys_getpid()) {
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| 65 | #ifndef __OS2__
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| 66 | if (pipe(select_pipe) == -1)
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| 67 | #else
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| 68 | if (socketpair(AF_UNIX, SOCK_STREAM,0, select_pipe) == -1)
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| 69 | #endif
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| 70 | {
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| 71 | DEBUG(0, ("sys_select: pipe failed (%s)\n",
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| 72 | strerror(errno)));
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| 73 | if (readfds != NULL)
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