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 3 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, see <http://www.gnu.org/licenses/>.
23 /* This is here because it allows us to avoid a nasty race in signal handling.
24 We need to guarantee that when we get a signal we get out of a select immediately
25 but doing that involves a race condition. We can avoid the race by getting the
26 signal handler to write to a pipe that is in the select/poll list
28 This means all Samba signal handlers should call sys_select_signal().
31 static pid_t initialised
;
32 static int select_pipe
[2];
33 static volatile unsigned pipe_written
, pipe_read
;
35 /*******************************************************************
36 Call this from all Samba signal handlers if you want to avoid a
37 nasty signal race condition.
38 ********************************************************************/
40 void sys_select_signal(char c
)
42 int saved_errno
= errno
;
44 if (!initialised
) return;
46 if (pipe_written
> pipe_read
+256) return;
48 if (write(select_pipe
[1], &c
, 1) == 1) pipe_written
++;
53 /*******************************************************************
54 Like select() but avoids the signal race using a pipe
55 it also guuarantees that fds on return only ever contains bits set
56 for file descriptors that were readable.
57 ********************************************************************/
59 int sys_select(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
62 fd_set
*readfds2
, readfds_buf
;
64 if (initialised
!= sys_getpid()) {
65 if (pipe(select_pipe
) == -1)
67 DEBUG(0, ("sys_select: pipe failed (%s)\n",
79 * These next two lines seem to fix a bug with the Linux
80 * 2.0.x kernel (and probably other UNIXes as well) where
81 * the one byte read below can block even though the
82 * select returned that there is data in the pipe and
83 * the pipe_written variable was incremented. Thanks to
84 * HP for finding this one. JRA.
87 if(set_blocking(select_pipe
[0],0)==-1)
88 smb_panic("select_pipe[0]: O_NONBLOCK failed");
89 if(set_blocking(select_pipe
[1],0)==-1)
90 smb_panic("select_pipe[1]: O_NONBLOCK failed");
92 initialised
= sys_getpid();
95 maxfd
= MAX(select_pipe
[0]+1, maxfd
);
97 /* If readfds is NULL we need to provide our own set. */
101 readfds2
= &readfds_buf
;
104 FD_SET(select_pipe
[0], readfds2
);
107 ret
= select(maxfd
,readfds2
,writefds
,errorfds
,tval
);
115 } else if (FD_ISSET(select_pipe
[0], readfds2
)) {
118 if (read(select_pipe
[0], &c
, 1) == 1) {
120 /* Mark Weaver <mark-clist@npsl.co.uk> pointed out a critical
121 fix to ensure we don't lose signals. We must always
122 return -1 when the select pipe is set, otherwise if another
123 fd is also ready (so ret == 2) then we used to eat the
124 byte in the pipe and lose the signal. JRA.
128 /* JRA - we can use this to debug the signal messaging... */
129 DEBUG(0,("select got %u signal\n", (unsigned int)c
));
133 FD_CLR(select_pipe
[0], readfds2
);
142 /*******************************************************************
143 Similar to sys_select() but catch EINTR and continue.
144 This is what sys_select() used to do in Samba.
145 ********************************************************************/
147 int sys_select_intr(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
150 fd_set
*readfds2
, readfds_buf
, *writefds2
, writefds_buf
, *errorfds2
, errorfds_buf
;
151 struct timeval tval2
, *ptval
, end_time
;
153 readfds2
= (readfds
? &readfds_buf
: NULL
);
154 writefds2
= (writefds
? &writefds_buf
: NULL
);
155 errorfds2
= (errorfds
? &errorfds_buf
: NULL
);
157 GetTimeOfDay(&end_time
);
158 end_time
.tv_sec
+= tval
->tv_sec
;
159 end_time
.tv_usec
+= tval
->tv_usec
;
160 end_time
.tv_sec
+= end_time
.tv_usec
/ 1000000;
161 end_time
.tv_usec
%= 1000000;
171 readfds_buf
= *readfds
;
173 writefds_buf
= *writefds
;
175 errorfds_buf
= *errorfds
;
176 if (ptval
&& (errno
== EINTR
)) {
177 struct timeval now_time
;
180 GetTimeOfDay(&now_time
);
181 tdif
= usec_time_diff(&end_time
, &now_time
);
183 ret
= 0; /* time expired. */
186 ptval
->tv_sec
= tdif
/ 1000000;
187 ptval
->tv_usec
= tdif
% 1000000;
190 /* We must use select and not sys_select here. If we use
191 sys_select we'd lose the fact a signal occurred when sys_select
192 read a byte from the pipe. Fix from Mark Weaver
193 <mark-clist@npsl.co.uk>
195 ret
= select(maxfd
, readfds2
, writefds2
, errorfds2
, ptval
);
196 } while (ret
== -1 && errno
== EINTR
);
199 *readfds
= readfds_buf
;
201 *writefds
= writefds_buf
;
203 *errorfds
= errorfds_buf
;