--- /dev/null
+/*
+ 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 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(char c)
+{
+ 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 *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
+{
+ int ret, saved_errno;
+ fd_set *readfds2, readfds_buf;
+
+ 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);
+
+ /* If readfds is NULL we need to provide our own set. */
+ if (readfds) {
+ readfds2 = readfds;
+ } else {
+ readfds2 = &readfds_buf;
+ FD_ZERO(readfds2);
+ }
+ FD_SET(select_pipe[0], readfds2);
+
+ errno = 0;
+ ret = select(maxfd,readfds2,writefds,errorfds,tval);
+
+ if (ret <= 0) {
+ FD_ZERO(readfds2);
+ if (writefds)
+ FD_ZERO(writefds);
+ if (errorfds)
+ FD_ZERO(errorfds);
+ } else if (FD_ISSET(select_pipe[0], readfds2)) {
+ char c;
+ saved_errno = errno;
+ if (read(select_pipe[0], &c, 1) == 1) {
+ pipe_read++;
+ /* Mark Weaver <mark-clist@npsl.co.uk> pointed out a critical
+ fix to ensure we don't lose signals. We must always
+ return -1 when the select pipe is set, otherwise if another
+ fd is also ready (so ret == 2) then we used to eat the
+ byte in the pipe and lose the signal. JRA.
+ */
+ ret = -1;
+#if 0
+ /* JRA - we can use this to debug the signal messaging... */
+ DEBUG(0,("select got %u signal\n", (unsigned int)c));
+#endif
+ errno = EINTR;
+ } else {
+ FD_CLR(select_pipe[0], readfds2);
+ ret--;
+ 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 *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *tval)
+{
+ int ret;
+ fd_set *readfds2, readfds_buf, *writefds2, writefds_buf, *errorfds2, errorfds_buf;
+ struct timeval tval2, *ptval, end_time;
+
+ readfds2 = (readfds ? &readfds_buf : NULL);
+ writefds2 = (writefds ? &writefds_buf : NULL);
+ errorfds2 = (errorfds ? &errorfds_buf : NULL);
+ if (tval) {
+ GetTimeOfDay(&end_time);
+ end_time.tv_sec += tval->tv_sec;
+ end_time.tv_usec += tval->tv_usec;
+ end_time.tv_sec += end_time.tv_usec / 1000000;
+ end_time.tv_usec %= 1000000;
+ errno = 0;
+ tval2 = *tval;
+ ptval = &tval2;
+ } else {
+ ptval = NULL;
+ }
+
+ do {
+ if (readfds)
+ readfds_buf = *readfds;
+ if (writefds)
+ writefds_buf = *writefds;
+ if (errorfds)
+ errorfds_buf = *errorfds;
+ if (ptval && (errno == EINTR)) {
+ struct timeval now_time;
+ SMB_BIG_INT tdif;
+
+ GetTimeOfDay(&now_time);
+ tdif = usec_time_diff(&end_time, &now_time);
+ if (tdif <= 0) {
+ ret = 0; /* time expired. */
+ break;
+ }
+ ptval->tv_sec = tdif / 1000000;
+ ptval->tv_usec = tdif % 1000000;
+ }
+
+ /* We must use select and not sys_select here. If we use
+ sys_select we'd lose the fact a signal occurred when sys_select
+ read a byte from the pipe. Fix from Mark Weaver
+ <mark-clist@npsl.co.uk>
+ */
+ ret = select(maxfd, readfds2, writefds2, errorfds2, ptval);
+ } while (ret == -1 && errno == EINTR);
+
+ if (readfds)
+ *readfds = readfds_buf;
+ if (writefds)
+ *writefds = writefds_buf;
+ if (errorfds)
+ *errorfds = errorfds_buf;
+
+ return ret;
+}
projects / samba / blobdiff