1 files changed, 128 insertions, 0 deletions
diff --git a/source/lib/select.c b/source/lib/select.c
new file mode 100644
index 00000000000..5e85d113513
--- /dev/null
+++ b/source/lib/select.c
@@ -0,0 +1,128 @@
+/* 
+   Unix SMB/CIFS implementation.
+   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 pid_t initialised;
+static int select_pipe[2];
+static VOLATILE 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 guarantees 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, saved_errno;
+
+	if (initialised != sys_getpid()) {
+		pipe(select_pipe);
+
+		/*
+		 * These next two lines seem to fix a bug with the Linux
+		 * 2.0.x kernel (and probably other UNIXes as well) where
+		 * the one byte read below can block even though the
+		 * select returned that there is data in the pipe and
+		 * the pipe_written variable was incremented. Thanks to
+		 * HP for finding this one. JRA.
+		 */
+
+		if(set_blocking(select_pipe[0],0)==-1)
+			smb_panic("select_pipe[0]: O_NONBLOCK failed.\n");
+		if(set_blocking(select_pipe[1],0)==-1)
+			smb_panic("select_pipe[1]: O_NONBLOCK failed.\n");
+
+		initialised = sys_getpid();
+	}
+
+	maxfd = MAX(select_pipe[0]+1, 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;
+		}
+	}
+
+	saved_errno = errno;
+
+	while (pipe_written != pipe_read) {
+		char c;
+		/* Due to the linux kernel bug in 2.0.x, we
+		 * always increment here even if the read failed... */
+		read(select_pipe[0], &c, 1);
+		pipe_read++;
+	}
+
+	errno = saved_errno;
+
+	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;
+}