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authorAndrew Tridgell <tridge@samba.org>2000-06-13 03:29:36 +0000
committerAndrew Tridgell <tridge@samba.org>2000-06-13 03:29:36 +0000
commit5dc618460deed8c9d4abf3196963b434627a52a7 (patch)
treefffabc534dae39c700509f942468af6c386a3d84 /source3/lib
parent60785b56e8e637e75d5e94a0aec021ce40177834 (diff)
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forgot to checkin select.c
(This used to be commit 719bc2f130393a55058f5c45ca6fbd30a78de2dc)
Diffstat (limited to 'source3/lib')
-rw-r--r--source3/lib/select.c107
1 files changed, 107 insertions, 0 deletions
diff --git a/source3/lib/select.c b/source3/lib/select.c
new file mode 100644
index 0000000000..cd77d1209f
--- /dev/null
+++ b/source3/lib/select.c
@@ -0,0 +1,107 @@
+/*
+ Unix SMB/Netbios implementation.
+ Version 3.0
+ Samba select/poll implementation
+ Copyright (C) Andrew Tridgell 1992-1998
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "includes.h"
+
+/* this is here because it allows us to avoid a nasty race in signal handling.
+ We need to guarantee that when we get a signal we get out of a select immediately
+ but doing that involves a race condition. We can avoid the race by getting the
+ signal handler to write to a pipe that is in the select/poll list
+
+ this means all Samba signal handlers should call sys_select_signal()
+*/
+static int initialised;
+static int select_pipe[2];
+static unsigned pipe_written, pipe_read;
+
+
+/*******************************************************************
+call this from all Samba signal handlers if you want to avoid a
+nasty signal race condition
+********************************************************************/
+void sys_select_signal(void)
+{
+ char c = 1;
+ if (!initialised) return;
+
+ if (pipe_written > pipe_read+256) return;
+
+ if (write(select_pipe[1], &c, 1) == 1) pipe_written++;
+}
+
+/*******************************************************************
+like select() but avoids the signal race using a pipe
+it also guuarantees that fds on return only ever contains bits set
+for file descriptors that were readable
+********************************************************************/
+int sys_select(int maxfd, fd_set *fds,struct timeval *tval)
+{
+ int ret;
+
+ if (!initialised) {
+ initialised = 1;
+ pipe(select_pipe);
+ }
+
+ maxfd = MAX(select_pipe[0], maxfd);
+ FD_SET(select_pipe[0], fds);
+ errno = 0;
+ ret = select(maxfd,fds,NULL,NULL,tval);
+
+ if (ret <= 0) {
+ FD_ZERO(fds);
+ }
+
+ if (FD_ISSET(select_pipe[0], fds)) {
+ FD_CLR(select_pipe[0], fds);
+ ret--;
+ if (ret == 0) {
+ ret = -1;
+ errno = EINTR;
+ }
+ }
+
+ while (pipe_written != pipe_read) {
+ char c;
+ if (read(select_pipe[0], &c, 1) == 1) pipe_read++;
+ }
+
+ return ret;
+}
+
+/*******************************************************************
+similar to sys_select() but catch EINTR and continue
+this is what sys_select() used to do in Samba
+********************************************************************/
+int sys_select_intr(int maxfd, fd_set *fds,struct timeval *tval)
+{
+ int ret;
+ fd_set fds2;
+
+ do {
+ fds2 = *fds;
+ ret = sys_select(maxfd, &fds2, tval);
+ } while (ret == -1 && errno == EINTR);
+
+ *fds = fds2;
+
+ return ret;
+}