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 if (!initialised
) return;
44 if (pipe_written
> pipe_read
+256) return;
46 if (write(select_pipe
[1], &c
, 1) == 1) pipe_written
++;
49 /*******************************************************************
50 Like select() but avoids the signal race using a pipe
51 it also guuarantees that fds on return only ever contains bits set
52 for file descriptors that were readable.
53 ********************************************************************/
55 int sys_select(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
58 fd_set
*readfds2
, readfds_buf
;
60 if (initialised
!= sys_getpid()) {
61 if (pipe(select_pipe
) == -1)
63 DEBUG(0, ("sys_select: pipe failed (%s)\n",
75 * These next two lines seem to fix a bug with the Linux
76 * 2.0.x kernel (and probably other UNIXes as well) where
77 * the one byte read below can block even though the
78 * select returned that there is data in the pipe and
79 * the pipe_written variable was incremented. Thanks to
80 * HP for finding this one. JRA.
83 if(set_blocking(select_pipe
[0],0)==-1)
84 smb_panic("select_pipe[0]: O_NONBLOCK failed");
85 if(set_blocking(select_pipe
[1],0)==-1)
86 smb_panic("select_pipe[1]: O_NONBLOCK failed");
88 initialised
= sys_getpid();
91 maxfd
= MAX(select_pipe
[0]+1, maxfd
);
93 /* If readfds is NULL we need to provide our own set. */
97 readfds2
= &readfds_buf
;
100 FD_SET(select_pipe
[0], readfds2
);
103 ret
= select(maxfd
,readfds2
,writefds
,errorfds
,tval
);
111 } else if (FD_ISSET(select_pipe
[0], readfds2
)) {
114 if (read(select_pipe
[0], &c
, 1) == 1) {
116 /* Mark Weaver <mark-clist@npsl.co.uk> pointed out a critical
117 fix to ensure we don't lose signals. We must always
118 return -1 when the select pipe is set, otherwise if another
119 fd is also ready (so ret == 2) then we used to eat the
120 byte in the pipe and lose the signal. JRA.
124 /* JRA - we can use this to debug the signal messaging... */
125 DEBUG(0,("select got %u signal\n", (unsigned int)c
));
129 FD_CLR(select_pipe
[0], readfds2
);
138 /*******************************************************************
139 Similar to sys_select() but catch EINTR and continue.
140 This is what sys_select() used to do in Samba.
141 ********************************************************************/
143 int sys_select_intr(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
146 fd_set
*readfds2
, readfds_buf
, *writefds2
, writefds_buf
, *errorfds2
, errorfds_buf
;
147 struct timeval tval2
, *ptval
, end_time
;
149 readfds2
= (readfds
? &readfds_buf
: NULL
);
150 writefds2
= (writefds
? &writefds_buf
: NULL
);
151 errorfds2
= (errorfds
? &errorfds_buf
: NULL
);
153 GetTimeOfDay(&end_time
);
154 end_time
.tv_sec
+= tval
->tv_sec
;
155 end_time
.tv_usec
+= tval
->tv_usec
;
156 end_time
.tv_sec
+= end_time
.tv_usec
/ 1000000;
157 end_time
.tv_usec
%= 1000000;
167 readfds_buf
= *readfds
;
169 writefds_buf
= *writefds
;
171 errorfds_buf
= *errorfds
;
172 if (ptval
&& (errno
== EINTR
)) {
173 struct timeval now_time
;
176 GetTimeOfDay(&now_time
);
177 tdif
= usec_time_diff(&end_time
, &now_time
);
179 ret
= 0; /* time expired. */
182 ptval
->tv_sec
= tdif
/ 1000000;
183 ptval
->tv_usec
= tdif
% 1000000;
186 /* We must use select and not sys_select here. If we use
187 sys_select we'd lose the fact a signal occurred when sys_select
188 read a byte from the pipe. Fix from Mark Weaver
189 <mark-clist@npsl.co.uk>
191 ret
= select(maxfd
, readfds2
, writefds2
, errorfds2
, ptval
);
192 } while (ret
== -1 && errno
== EINTR
);
195 *readfds
= readfds_buf
;
197 *writefds
= writefds_buf
;
199 *errorfds
= errorfds_buf
;