Files
xen/tools/console/daemon/main.c
T
Keir Fraser fd6c8de67e console: Provide option to stall the inter-domain console ring rather
than discard characters in the console daemon buffers.

New option: -o, --overflow-data=discard|keep

This option changes the behaviour when dealing with data that overflow
the max capacity of the buffer. If overflow-data is set to discard
(the default), the current behaviour is used: we discard some data in
the middle of the buffer.

If overflow-data is set to keep, we stop listening to the ring until
we free some space in the buffer. This can cause the ring to fill up
and the guest kernel internal buffer to fill up as well. When this
happens the guest kernel stops reading characters from the console
device so the application generating data hangs. When xenconsoled
resumes reading from the ring, the guest kernel will be able to resume
reading from the console device as well. At that point the guest
application will be allowed to continue.

The risk of making this behaviour the default is that existing kernel
drivers may assume they can rely on timely ring updates by the console
daemon and thus themselves block on the ring being emptied.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
2008-04-22 10:34:55 +01:00

180 lines
3.9 KiB
C

/*\
* Copyright (C) International Business Machines Corp., 2005
* Author(s): Anthony Liguori <aliguori@us.ibm.com>
*
* Xen Console Daemon
*
* 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; under version 2 of the License.
*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
\*/
#include <getopt.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <sys/types.h>
#include "xenctrl.h"
#include "utils.h"
#include "io.h"
int log_reload = 0;
int log_guest = 0;
int log_hv = 0;
int log_time_hv = 0;
int log_time_guest = 0;
char *log_dir = NULL;
int discard_overflowed_data = 1;
static void handle_hup(int sig)
{
log_reload = 1;
}
static void usage(char *name)
{
printf("Usage: %s [-h] [-V] [-v] [-i] [--log=none|guest|hv|all] [--log-dir=DIR] [--pid-file=PATH] [-t, --timestamp=none|guest|hv|all] [-o, --overflow-data=discard|keep]\n", name);
}
static void version(char *name)
{
printf("Xen Console Daemon 3.0\n");
}
int main(int argc, char **argv)
{
const char *sopts = "hVvit:o:";
struct option lopts[] = {
{ "help", 0, 0, 'h' },
{ "version", 0, 0, 'V' },
{ "verbose", 0, 0, 'v' },
{ "interactive", 0, 0, 'i' },
{ "log", 1, 0, 'l' },
{ "log-dir", 1, 0, 'r' },
{ "pid-file", 1, 0, 'p' },
{ "timestamp", 1, 0, 't' },
{ "overflow-data", 1, 0, 'o'},
{ 0 },
};
bool is_interactive = false;
int ch;
int syslog_option = LOG_CONS;
int syslog_mask = LOG_WARNING;
int opt_ind = 0;
char *pidfile = NULL;
while ((ch = getopt_long(argc, argv, sopts, lopts, &opt_ind)) != -1) {
switch (ch) {
case 'h':
usage(argv[0]);
exit(0);
case 'V':
version(argv[0]);
exit(0);
case 'v':
syslog_option |= LOG_PERROR;
syslog_mask = LOG_DEBUG;
break;
case 'i':
is_interactive = true;
break;
case 'l':
if (!strcmp(optarg, "all")) {
log_hv = 1;
log_guest = 1;
} else if (!strcmp(optarg, "hv")) {
log_hv = 1;
} else if (!strcmp(optarg, "guest")) {
log_guest = 1;
}
break;
case 'r':
log_dir = strdup(optarg);
break;
case 'p':
pidfile = strdup(optarg);
break;
case 't':
if (!strcmp(optarg, "all")) {
log_time_hv = 1;
log_time_guest = 1;
} else if (!strcmp(optarg, "hv")) {
log_time_hv = 1;
} else if (!strcmp(optarg, "guest")) {
log_time_guest = 1;
} else if (!strcmp(optarg, "none")) {
log_time_guest = 0;
log_time_hv = 0;
}
break;
case 'o':
if (!strcmp(optarg, "keep")) {
discard_overflowed_data = 0;
} else if (!strcmp(optarg, "discard")) {
discard_overflowed_data = 1;
}
break;
case '?':
fprintf(stderr,
"Try `%s --help' for more information\n",
argv[0]);
exit(EINVAL);
}
}
if (!log_dir) {
log_dir = strdup("/var/log/xen/console");
}
if (geteuid() != 0) {
fprintf(stderr, "%s requires root to run.\n", argv[0]);
exit(EPERM);
}
signal(SIGHUP, handle_hup);
openlog("xenconsoled", syslog_option, LOG_DAEMON);
setlogmask(syslog_mask);
if (!is_interactive) {
daemonize(pidfile ? pidfile : "/var/run/xenconsoled.pid");
}
if (!xen_setup())
exit(1);
enum_domains();
handle_io();
closelog();
free(log_dir);
free(pidfile);
return 0;
}
/*
* Local variables:
* c-file-style: "linux"
* indent-tabs-mode: t
* c-indent-level: 8
* c-basic-offset: 8
* tab-width: 8
* End:
*/