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, 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(char c)
43 if (!initialised) return;
45 if (pipe_written > pipe_read+256) return;
47 if (write(select_pipe[1], &c, 1) == 1) pipe_written++;
50 /*******************************************************************
51 Like select() but avoids the signal race using a pipe
52 it also guuarantees that fds on return only ever contains bits set
53 for file descriptors that were readable.
54 ********************************************************************/
56 int sys_select(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
59 fd_set *readfds2, readfds_buf;
61 if (initialised != sys_getpid()) {
65 * These next two lines seem to fix a bug with the Linux
66 * 2.0.x kernel (and probably other UNIXes as well) where
67 * the one byte read below can block even though the
68 * select returned that there is data in the pipe and
69 * the pipe_written variable was incremented. Thanks to
70 * HP for finding this one. JRA.
73 if(set_blocking(select_pipe[0],0)==-1)
74 smb_panic("select_pipe[0]: O_NONBLOCK failed");
75 if(set_blocking(select_pipe[1],0)==-1)
76 smb_panic("select_pipe[1]: O_NONBLOCK failed");
78 initialised = sys_getpid();
81 maxfd = MAX(select_pipe[0]+1, maxfd);
83 /* If readfds is NULL we need to provide our own set. */
87 readfds2 = &readfds_buf;
90 FD_SET(select_pipe[0], readfds2);
93 ret = select(maxfd,readfds2,writefds,errorfds,tval);
101 } else if (FD_ISSET(select_pipe[0], readfds2)) {
104 if (read(select_pipe[0], &c, 1) == 1) {
106 /* Mark Weaver <mark-clist@npsl.co.uk> pointed out a critical
107 fix to ensure we don't lose signals. We must always
108 return -1 when the select pipe is set, otherwise if another
109 fd is also ready (so ret == 2) then we used to eat the
110 byte in the pipe and lose the signal. JRA.
114 /* JRA - we can use this to debug the signal messaging... */
115 DEBUG(0,("select got %u signal\n", (unsigned int)c));
119 FD_CLR(select_pipe[0], readfds2);
128 /*******************************************************************
129 Similar to sys_select() but catch EINTR and continue.
130 This is what sys_select() used to do in Samba.
131 ********************************************************************/
133 int sys_select_intr(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
136 fd_set *readfds2, readfds_buf, *writefds2, writefds_buf, *errorfds2, errorfds_buf;
137 struct timeval tval2, *ptval, end_time;
139 readfds2 = (readfds ? &readfds_buf : NULL);
140 writefds2 = (writefds ? &writefds_buf : NULL);
141 errorfds2 = (errorfds ? &errorfds_buf : NULL);
143 GetTimeOfDay(&end_time);
144 end_time.tv_sec += tval->tv_sec;
145 end_time.tv_usec += tval->tv_usec;
146 end_time.tv_sec += end_time.tv_usec / 1000000;
147 end_time.tv_usec %= 1000000;
157 readfds_buf = *readfds;
159 writefds_buf = *writefds;
161 errorfds_buf = *errorfds;
162 if (ptval && (errno == EINTR)) {
163 struct timeval now_time;
166 GetTimeOfDay(&now_time);
167 tdif = usec_time_diff(&end_time, &now_time);
169 ret = 0; /* time expired. */
172 ptval->tv_sec = tdif / 1000000;
173 ptval->tv_usec = tdif % 1000000;
176 /* We must use select and not sys_select here. If we use
177 sys_select we'd lose the fact a signal occurred when sys_select
178 read a byte from the pipe. Fix from Mark Weaver
179 <mark-clist@npsl.co.uk>
181 ret = select(maxfd, readfds2, writefds2, errorfds2, ptval);
182 } while (ret == -1 && errno == EINTR);
185 *readfds = readfds_buf;
187 *writefds = writefds_buf;
189 *errorfds = errorfds_buf;