2 Unix SMB/Netbios implementation.
4 Samba select/poll implementation
5 Copyright (C) Andrew Tridgell 1992-1998
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.
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.
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., 675 Mass Ave, Cambridge, MA 02139, USA.
24 /* This is here because it allows us to avoid a nasty race in signal handling.
25 We need to guarantee that when we get a signal we get out of a select immediately
26 but doing that involves a race condition. We can avoid the race by getting the
27 signal handler to write to a pipe that is in the select/poll list
29 This means all Samba signal handlers should call sys_select_signal().
32 static pid_t initialised
;
33 static int select_pipe
[2];
34 static VOLATILE
unsigned pipe_written
, pipe_read
;
36 /*******************************************************************
37 Call this from all Samba signal handlers if you want to avoid a
38 nasty signal race condition.
39 ********************************************************************/
41 void sys_select_signal(void)
44 if (!initialised
) return;
46 if (pipe_written
> pipe_read
+256) return;
48 if (write(select_pipe
[1], &c
, 1) == 1) pipe_written
++;
51 /*******************************************************************
52 Like select() but avoids the signal race using a pipe
53 it also guuarantees that fds on return only ever contains bits set
54 for file descriptors that were readable.
55 ********************************************************************/
57 int sys_select(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
60 fd_set
*readfds2
, readfds_buf
;
62 if (initialised
!= sys_getpid()) {
66 * These next two lines seem to fix a bug with the Linux
67 * 2.0.x kernel (and probably other UNIXes as well) where
68 * the one byte read below can block even though the
69 * select returned that there is data in the pipe and
70 * the pipe_written variable was incremented. Thanks to
71 * HP for finding this one. JRA.
74 if(set_blocking(select_pipe
[0],0)==-1)
75 smb_panic("select_pipe[0]: O_NONBLOCK failed.\n");
76 if(set_blocking(select_pipe
[1],0)==-1)
77 smb_panic("select_pipe[1]: O_NONBLOCK failed.\n");
79 initialised
= sys_getpid();
82 maxfd
= MAX(select_pipe
[0]+1, maxfd
);
84 /* If readfds is NULL we need to provide our own set. */
88 readfds2
= &readfds_buf
;
91 FD_SET(select_pipe
[0], readfds2
);
94 ret
= select(maxfd
,readfds2
,writefds
,errorfds
,tval
);
104 if (FD_ISSET(select_pipe
[0], readfds2
)) {
107 if (read(select_pipe
[0], &c
, 1) == 1) {
111 FD_CLR(select_pipe
[0], readfds2
);
122 /*******************************************************************
123 Similar to sys_select() but catch EINTR and continue.
124 This is what sys_select() used to do in Samba.
125 ********************************************************************/
127 int sys_select_intr(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
130 fd_set
*readfds2
, readfds_buf
, *writefds2
, writefds_buf
, *errorfds2
, errorfds_buf
;
131 struct timeval tval2
, *ptval
;
133 readfds2
= (readfds
? &readfds_buf
: NULL
);
134 writefds2
= (writefds
? &writefds_buf
: NULL
);
135 errorfds2
= (errorfds
? &errorfds_buf
: NULL
);
136 ptval
= (tval
? &tval2
: NULL
);
140 readfds_buf
= *readfds
;
142 writefds_buf
= *writefds
;
144 errorfds_buf
= *errorfds
;
148 ret
= sys_select(maxfd
, readfds2
, writefds2
, errorfds2
, ptval
);
149 } while (ret
== -1 && errno
== EINTR
);
152 *readfds
= readfds_buf
;
154 *writefds
= writefds_buf
;
156 *errorfds
= errorfds_buf
;