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/>.
22 #include "system/filesys.h"
23 #include "system/select.h"
24 #include "lib/util/select.h"
26 /* This is here because it allows us to avoid a nasty race in signal handling.
27 We need to guarantee that when we get a signal we get out of a select immediately
28 but doing that involves a race condition. We can avoid the race by getting the
29 signal handler to write to a pipe that is in the select/poll list
31 This means all Samba signal handlers should call sys_select_signal().
34 static pid_t initialised
;
35 static int select_pipe
[2];
36 static volatile unsigned pipe_written
, pipe_read
;
38 /*******************************************************************
39 Call this from all Samba signal handlers if you want to avoid a
40 nasty signal race condition.
41 ********************************************************************/
43 void sys_select_signal(char c
)
45 int saved_errno
= errno
;
47 if (!initialised
) return;
49 if (pipe_written
> pipe_read
+256) return;
51 if (write(select_pipe
[1], &c
, 1) == 1) pipe_written
++;
56 /*******************************************************************
57 Like select() but avoids the signal race using a pipe
58 it also guuarantees that fds on return only ever contains bits set
59 for file descriptors that were readable.
60 ********************************************************************/
62 int sys_select(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
65 fd_set
*readfds2
, readfds_buf
;
67 if (initialised
!= sys_getpid()) {
68 if (pipe(select_pipe
) == -1)
70 DEBUG(0, ("sys_select: pipe failed (%s)\n",
82 * These next two lines seem to fix a bug with the Linux
83 * 2.0.x kernel (and probably other UNIXes as well) where
84 * the one byte read below can block even though the
85 * select returned that there is data in the pipe and
86 * the pipe_written variable was incremented. Thanks to
87 * HP for finding this one. JRA.
90 if(set_blocking(select_pipe
[0],0)==-1)
91 smb_panic("select_pipe[0]: O_NONBLOCK failed");
92 if(set_blocking(select_pipe
[1],0)==-1)
93 smb_panic("select_pipe[1]: O_NONBLOCK failed");
95 initialised
= sys_getpid();
98 maxfd
= MAX(select_pipe
[0]+1, maxfd
);
100 /* If readfds is NULL we need to provide our own set. */
104 readfds2
= &readfds_buf
;
107 FD_SET(select_pipe
[0], readfds2
);
110 ret
= select(maxfd
,readfds2
,writefds
,errorfds
,tval
);
118 } else if (FD_ISSET(select_pipe
[0], readfds2
)) {
121 if (read(select_pipe
[0], &c
, 1) == 1) {
123 /* Mark Weaver <mark-clist@npsl.co.uk> pointed out a critical
124 fix to ensure we don't lose signals. We must always
125 return -1 when the select pipe is set, otherwise if another
126 fd is also ready (so ret == 2) then we used to eat the
127 byte in the pipe and lose the signal. JRA.
131 /* JRA - we can use this to debug the signal messaging... */
132 DEBUG(0,("select got %u signal\n", (unsigned int)c
));
136 FD_CLR(select_pipe
[0], readfds2
);
145 /*******************************************************************
146 Similar to sys_select() but catch EINTR and continue.
147 This is what sys_select() used to do in Samba.
148 ********************************************************************/
150 int sys_select_intr(int maxfd
, fd_set
*readfds
, fd_set
*writefds
, fd_set
*errorfds
, struct timeval
*tval
)
153 fd_set
*readfds2
, readfds_buf
, *writefds2
, writefds_buf
, *errorfds2
, errorfds_buf
;
154 struct timeval tval2
, *ptval
;
155 struct timespec end_time
;
157 readfds2
= (readfds
? &readfds_buf
: NULL
);
158 writefds2
= (writefds
? &writefds_buf
: NULL
);
159 errorfds2
= (errorfds
? &errorfds_buf
: NULL
);
161 clock_gettime_mono(&end_time
);
162 end_time
.tv_sec
+= tval
->tv_sec
;
163 end_time
.tv_nsec
+= tval
->tv_usec
*1000;
164 end_time
.tv_sec
+= end_time
.tv_nsec
/ 1000000000;
165 end_time
.tv_nsec
%= 1000000000;
175 readfds_buf
= *readfds
;
177 writefds_buf
= *writefds
;
179 errorfds_buf
= *errorfds
;
180 if (ptval
&& (errno
== EINTR
)) {
181 struct timespec now_time
;
184 clock_gettime_mono(&now_time
);
185 tdif
= nsec_time_diff(&end_time
,&now_time
);
187 ret
= 0; /* time expired. */
190 ptval
->tv_sec
= tdif
/ 1000000000;
191 ptval
->tv_usec
= (tdif
% 1000000000) / 1000;
194 /* We must use select and not sys_select here. If we use
195 sys_select we'd lose the fact a signal occurred when sys_select
196 read a byte from the pipe. Fix from Mark Weaver
197 <mark-clist@npsl.co.uk>
199 ret
= select(maxfd
, readfds2
, writefds2
, errorfds2
, ptval
);
200 } while (ret
== -1 && errno
== EINTR
);
203 *readfds
= readfds_buf
;
205 *writefds
= writefds_buf
;
207 *errorfds
= errorfds_buf
;