With this monitor any process can request RT priorities.
If those (or other) processes overloads the system.
They will be returned to normal priorities.
Note:
* this code is still experimental. I had a complete
lockup because my busy system detection did not work...
(removed since it was not necessary)
* It does probably not work on SMP - I have not given it
much of a thought yet...
compile the source:
gcc -Wall rt.c -o rt
gcc -Wall rt_monitor.c -o rt_monitor
then as root:
mkfifo -m 622 /var/named/rt-request
./rt_monitor
start another shell (as a normal user - non root)
./rt
output from ./rt will look like this
policy 0 <- does not have RT priority
policy 0 <- request sent, waiting...
..
policy 1 <- got rt prio
<- sleeps for 5 s
<- lockup!!! (for about 4 s)
<- rt_monitor reduces the prio, rt exits when detected
/RogerL
--
Roger Larsson
Skellefteċ
Sweden
/* RT user.
Copyright (c) 2002 Roger Larsson <[EMAIL PROTECTED]>
This program is free software; you can redistribute it and/or
modify it under the terms of version 2 of the GNU General Public
License as published by the Free Software Foundation.
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.
Thanks to autor of KSysGuard Chris Schlaeger for borrowed code...
*/
#include <sys/types.h>
#include <sched.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
struct request
{
pid_t pid;
char _filler[32];
};
int main(int argc, char *argv[])
{
struct request request;
FILE *reqf;
reqf = fopen("/var/named/rt-request", "w");
if (reqf == NULL) {
perror("fopen");
return errno;
}
printf("policy %d\n", sched_getscheduler(0));
request.pid = getpid();
fwrite(&request, 32, 1, reqf);
fclose(reqf); // important!
printf("policy %d\n", sched_getscheduler(0));
while (sched_getscheduler(0) == 0) {
putchar('.');
sleep(1);
}
printf("\npolicy %d\n", sched_getscheduler(0));
// well behaved
sleep(5);
while (sched_getscheduler(0) != 0) {
// someone did listen to my request...
// assume monitor is running
}
return 0;
}
/* RT monitor.
Copyright (c) 2002 Roger Larsson <[EMAIL PROTECTED]>
This program is free software; you can redistribute it and/or
modify it under the terms of version 2 of the GNU General Public
License as published by the Free Software Foundation.
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.
Thanks to autor of KSysGuard Chris Schlaeger for borrowed code...
*/
#include <sys/types.h>
#include <sched.h>
#include <stdio.h>
#include <dirent.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/time.h>
#include <stdlib.h>
int set_normal_priority(pid_t pid);
int isRT(pid_t pid)
{
int sched_class = sched_getscheduler( pid);
if (sched_class == -1) {
fprintf(stderr, "Pid %d Exited?\n", pid);
return 0;
}
return sched_class != SCHED_OTHER;
}
struct rt_process_info
{
/* This flag is set for all found processes at the beginning of the
* process list update. Processes that do not have this flag set will
* be assumed dead and removed from the list. The flag is cleared after
* each list update. */
int alive;
int centStamp;
pid_t pid;
pid_t ppid;
gid_t gid;
unsigned int userTime;
unsigned int sysTime;
unsigned int vmSize; // enough?
unsigned int vmRss; // enough?
float sysLoad;
float userLoad;
float cpu_usage;
};
#define MAX_RT_PROCESSES 200
struct rt_process_info rt_process[MAX_RT_PROCESSES]; /* pid & alive == 0 */
struct rt_process_info *find_process(pid_t pid)
{
unsigned ix;
for (ix = 0; ix < MAX_RT_PROCESSES; ix++)
{
if (rt_process[ix].pid == pid) {
rt_process[ix].alive = 1;
return &rt_process[ix];
}
}
return NULL;
}
struct rt_process_info *new_process(pid_t pid)
{
unsigned ix;
for (ix = 0; ix < MAX_RT_PROCESSES; ix++)
{
if (rt_process[ix].pid == 0) {
rt_process[ix].pid = pid;
rt_process[ix].alive = 2;
return &rt_process[ix];
}
}
return NULL;
}
float cpu_usage(struct rt_process_info *ps)
{
#define BUFSIZE 1024
char buf[BUFSIZE];
FILE *fd;
char status;
unsigned int userTime, sysTime;
snprintf(buf, BUFSIZE - 1, "/proc/%d/stat", ps->pid);
buf[BUFSIZE - 1] = '\0';
if ((fd = fopen(buf, "r")) == 0)
return (-1);
if (fscanf(fd, "%*d %*s %c %d %d %*d %*d %*d %*u %*u %*u %*u %*u %d %d"
"%*d %*d %*d %*d %*u %*u %*d %u %u",
&status, (int*) &ps->ppid, (int*) &ps->gid,
&userTime, &sysTime, &ps->vmSize,
&ps->vmRss) != 7) {
fclose(fd);
return (-1);
}
if (fclose(fd))
return (-1);
{
unsigned int newCentStamp;
int timeDiff, userDiff, sysDiff;
struct timeval tv;
gettimeofday(&tv, 0);
newCentStamp = tv.tv_sec * 100 + tv.tv_usec / 10000;
// calculate load
if (ps->alive == 2)
ps->sysLoad = ps->userLoad = 0.0f; /* can't give relieable number at the moment... */
else {
timeDiff = (int)(newCentStamp - ps->centStamp);
userDiff = userTime - ps->userTime;
sysDiff = sysTime - ps->sysTime;
if ((timeDiff > 0) && (userDiff >= 0) && (sysDiff >= 0)) /* protect from bad data */
{
ps->userLoad = ((double) userDiff / timeDiff) * 100.0;
ps->sysLoad = ((double) sysDiff / timeDiff) * 100.0;
}
else
ps->sysLoad = ps->userLoad = 0.0;
}
// update fields
ps->centStamp = newCentStamp;
ps->userTime = userTime;
ps->sysTime = sysTime;
}
ps->cpu_usage = ps->userLoad + ps->sysLoad;
return ps->cpu_usage;
}
float process_cpu_usage(pid_t pid)
{
struct rt_process_info *process = find_process(pid);
float cpu_use;
if (process == NULL)
{
process = new_process(pid);
if (process == NULL) {
// to many RT processes!
// this process is new - assume a DOS attack
printf("Out of RT process info space - "
"assume DOS attack\n");
set_normal_priority(pid);
}
process->alive = 2; /* mark process new */
}
cpu_use = cpu_usage(process);
process->alive = 1;
return cpu_use;
}
/* process reading code from ksysguard */
float cpu_rt_usage(struct rt_process_info **rt_list_head)
{
// Watch out for SMP effects...
float result = 0.0f;
pid_t myself = getpid();
DIR* dir;
struct dirent* entry;
/* read in current process list via the /proc filesystem entry */
if ((dir = opendir("/proc")) == NULL)
{
perror("Cannot open directory \'/proc\'!\n"
"The kernel needs to be compiled with support\n"
"for /proc filesystem enabled!\n");
return 0;
}
// for all processes
while ((entry = readdir(dir)))
{
if (isdigit(entry->d_name[0]))
{
pid_t pid;
pid = atoi(entry->d_name);
if (pid != myself && isRT(pid)) {
result += process_cpu_usage(pid);
}
}
}
closedir(dir);
return result;
}
void gc_rt_processes()
{
unsigned ix;
for (ix = 0; ix < MAX_RT_PROCESSES; ix++)
{
struct rt_process_info *rt_examine = &rt_process[ix];
if (rt_examine->alive)
{
rt_examine->alive = 0;
}
else
{
rt_examine->pid = 0; /* delete it! */
}
}
}
int set_me_realtime(void)
{
struct sched_param schp;
/*
* set the process to realtime privs
*/
memset(&schp, 0, sizeof(schp));
schp.sched_priority = sched_get_priority_max(SCHED_FIFO);
if (sched_setscheduler(0, SCHED_FIFO, &schp) != 0) {
perror("sched_setscheduler");
return -1;
}
if(mlockall(MCL_CURRENT|MCL_FUTURE))
{
perror("mlockall() failed, exiting. mlock");
return -1;
}
return 0;
}
int set_realtime_priority(pid_t pid)
{
struct sched_param schp;
/*
* set the process to realtime privs
*/
printf("Attempt to set realtime for pid %d ", pid);
memset(&schp, 0, sizeof(schp));
schp.sched_priority = sched_get_priority_min(SCHED_FIFO);
if (sched_setscheduler(pid, SCHED_FIFO, &schp) != 0) {
printf("- failed!\n");
perror("sched_setscheduler");
return -1;
}
printf("- done!\n");
(void)process_cpu_usage(pid);
return 0;
}
int set_normal_priority(pid_t pid)
{
struct sched_param schp;
/*
* set the process to realtime privs
*/
memset(&schp, 0, sizeof(schp));
schp.sched_priority = 0;
printf("Attempt to reduce scheduling class for pid %d ", pid);
if (sched_setscheduler(pid, SCHED_OTHER, &schp) != 0) {
printf("- failed!\n");
perror("sched_setscheduler");
return -1;
}
printf("- done!\n");
return 0;
}
void set_normal_priority_all()
{
unsigned ix;
for (ix = 0; ix < MAX_RT_PROCESSES; ix++)
{
struct rt_process_info *process_info = &rt_process[ix];
if (process_info->pid)
set_normal_priority(process_info->pid);
}
}
struct request
{
pid_t pid;
char _filler[32];
};
#define REQUEST_SIZE 32
int poll_request(int reqfd)
{
// Be VERY careful not to
// * block here...
// * get buffer overruns...
static int remaining = REQUEST_SIZE;
static struct request request;
char *next = ((char *)&request + REQUEST_SIZE - remaining);
int ret = read(reqfd, (void *)next, remaining);
if (ret == -1) {
perror("read");
return 0;
}
remaining -= ret;
if (remaining == 0) {
remaining = REQUEST_SIZE;
if (request.pid == 0 || request.pid == getpid()) {
fputs("attempt to forge the monitor\n", stderr);
return 0;
}
set_realtime_priority(request.pid);
return 1;
}
return 0;
}
#define RTREQUEST_FILE "/var/named/rt-request"
int main(int argc, char * argv[])
{
struct rt_process_info *rt_list = NULL;
int reqfd = open(RTREQUEST_FILE, O_RDONLY | O_NONBLOCK | O_NDELAY);
if (reqfd == -1) {
perror("open " RTREQUEST_FILE);
fputs("have you created it? use 'mkfifo -m 622 " RTREQUEST_FILE "'\n", stderr);
exit(1);
}
// monitor process runs with realtime prio
set_me_realtime();
#define MIN_IDLE 10
#define MAX_RT_USAGE 70
while (1) {
poll_request(reqfd);
if (cpu_rt_usage(&rt_list) > MAX_RT_USAGE) {
printf("Total CPU RT usage above MAX_RT_USAGE\n");
gc_rt_processes();
// build process trees from rt_list
// decide which tree to reduce to normal prio class
// (assume only one for simplicitly...)
// reduce all processes in that tree
set_normal_priority_all();
// (may use nice to simulate prio levels)
// log a message
}
sleep(2);
}
// process exiting - free elements on rt_list...
//free_rt_list(rt_list);
}
