Yes, I agree that X may be in the way. It is also possible, if you are
logging in via telnet or some other remote service that the I/O service
tasks don't have the needed priority.
My solution for X is to bump its priority too.
Attached, find rt, a program to allow you to change the priority of any
task, and getrt a simple reporting program to get the priority of any
task.
By the way, if you have a relatively secure system, and you want to use
telnet, you can set the priority of inetd. This way all the I/O
services and the resulting session are boosted in priority. You must do
this ahead of time, after your task goes into a loop, its too late to
boost anything, but once you do this, you should be able to telnet into
the machine even if your task is "lost" in some loop.
-g
Nicolas Bonnefon wrote:
>
> > My application uses the possibility to change scheduling mechanism. When
> > changing from SCHED_OTHER to SCHED_FIFO or SCHED_RR, my application causes
> > the whole Linux PC to "hang". Prior to launching my own application, I
> > launch a "superbash" application with higher priority than my own
> > application. But I am not able to switch to the window where this
> > "superbash" application is running to kill my own application. The PC
> > simply does not respond to any input from the keyboard.
>
> Have you tried without running X ?
> A SCHED_FIFO or SCHED_RR task has ALWAYS priority over any SCHED_OTHER
> task, so if your application sits in an infinite loop without blocking, the
> window manager cannot preempt it and you simply cannot switch x-term.
> I think you should carefully debug your app in SCHED_OTHER mode first, and
> then switch to some real-time policy.
>
> >
> > I have used this mechanism before, and I am quite confident that this
> > worked under kernel 2.4.2. Are you aware of anything that could explain
> > this behaviour?
>
> It would be surprising, but if you were sure of that, it would deserve some
> deeper investigations !
>
> Regards
> --
> Nicolas Bonnefon
> Radar Development/Digital Processing Engineer
> Thales Air Defence - 7-9 rue des Mathurins
> 92223 Bagneux - France
> -
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-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Real time sched: http://sourceforge.net/projects/rtsched/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
#include <sched.h> #include <stdlib.h>
main(int args,char* argc[]) { struct sched_param p; pid_t pid;
int policy; int prio,max_prio,max_rt_prio; char * cpolicy;
if (args < 2) { pid = 0; }else{ pid = atoi(argc[1]); } policy = sched_getscheduler(pid); sched_getparam(pid,&p); prio = p.sched_priority; max_prio = sched_get_priority_max(policy); max_rt_prio = sched_get_priority_max(SCHED_FIFO);
switch(policy){ case SCHED_OTHER: cpolicy = "SCHED_OTHER"; break; case SCHED_RR: cpolicy = "SCHED_RR"; break; case SCHED_FIFO: cpolicy = "SCHED_FIFO"; break; default: perror("sched_getscheduler"); exit(1); } if (policy == SCHED_OTHER){ printf("%s at priority %d (MAX_PRIO(%s) = %d, MAX_PRIO(SCHED_FIFO) = %d)\n", cpolicy, prio, cpolicy,max_prio, max_rt_prio); }else{ printf("%s at priority %d (MAX_PRIO(%s) = %d)\n", cpolicy, prio, cpolicy, max_prio); } exit(0); }
/* rt - a utility to set the realtime priority and scheduling policy */
/* includes */ #include <stdio.h> #include <stdlib.h> #include <sched.h> #include <unistd.h> #define _GNU_LIBRARY__ #include <getopt.h>
/* defines */
#define RUNSTRING "usage: rt [-f] [-v] prio [--] runstring \n \ or: rt [-f] [-v] -p PID prio\\ \n\n \ where: prio specifies the realtime priority \n \ -f set scheduling policy to SCHED_FIFO \n \ -v turns on verbose mode. \n \ -p PID specifies an existing process to modify \n \ runstring is a process and parameters \n \ (use '--' if runstring contains options). \n"
#define POLICY(x) x ? x-1 ? "SCHED_RR" : "SCHED_FIFO" : "SCHED_OTHER"
/* prototypes */ void print_usage(char *[]);
/* globals */ int verbose=0; /* 0=none, !0=verbose */
main(int argc, char *argv[]) { struct sched_param prio_struct; int policy = -1; int pid = 0; int pidopt = 0; int optprobs = 0; /* problems parsing? */ int c; /* generic single character */
/* "standard" option parsing... */ while ( (c=getopt(argc, argv, "+fp:v?")) != EOF) { switch (c) { case 'f': /* set FIFO mode */ policy = SCHED_FIFO; break; case 'p': /* read PID */ sscanf(optarg,"%d",&pid); pidopt=1; break; case 'v': verbose=1; /* verbosity */ break; case '?': /* help? */ printf("%s",RUNSTRING); exit(0); default: /* something went wrong */ optprobs=1; /* we'll deal with this problem later */ break; } }
if (optprobs) { fprintf(stderr,RUNSTRING); exit(1); }
if((argc - optind) < 2-pidopt) { print_usage(argv); }
sscanf(argv[optind], "%d", &(prio_struct.sched_priority));
/* sanity checking... */ if ( (prio_struct.sched_priority != 0) && (policy < 0 ) ) { policy=SCHED_RR; if (verbose) printf("Defaulting sched policy to %s.\n", POLICY(policy)); }
if ( (prio_struct.sched_priority == 0 ) && (policy != SCHED_OTHER) ) { policy=SCHED_OTHER; fprintf(stderr,"Priority of %d implies sched policy of %s.\n", prio_struct.sched_priority, POLICY(policy)); }
policy = (prio_struct.sched_priority)? policy : SCHED_OTHER; if( sched_setscheduler(pid,policy,&prio_struct)){ perror("Priority out of range"); print_usage(argv); } if ( pid ) exit(0); argv+=optind; /* adjust argv to point to the runstring */ argv++; execvp(argv[0],argv); perror("exec failed.."); }
void print_usage(char * who[]) { printf("%s",RUNSTRING); exit (1); }
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue Apr 30 2002 - 22:00:13 EST