Re: sched_setscheduler(2)

[Kevin D. Clark]

Strange.  I made a few minor changes (see attached patch)
and when I run your code on my test machine running Linux kernel
2.6.35 I get the following output:

  $ sudo ./latencytest
  ./latencytest starting...
  My original scheduling policy is SCHED_OTHER (0)
  The original minimum scheduling priority is 0, the maximum is 0
  sched_get_priority_max(1) returned 99
  sched_get_priority_min(1) returned 1
  My target scheduling policy is SCHED_FIFO (1)
  The target minimum scheduling priority is 1, the maximum is 99
  params.sched_priority now set to 98
  It worked - now running in high-priority mode
  params.sched_priority now set to 98
  Now running at original scheduler policy
  My scheduling policy is SCHED_OTHER
  The minimum scheduling priority is 0, the maximum is 0
  $ 

We'll have to look deeper.  Of course, the first thing that comes to
mind is that you are running a 3.x kernel, and I am not (yet).

Regards,

--kevin
-- 
alumni.unh.edu!kdc / http://kdc-blog.blogspot.com/
GnuPG: D87F DAD6 0291 289C EB1E 781C 9BF8 A7D8 B280 F24E

And the Army Ants, they leave nothin' but the bones...
   -- Tom Waits




--- latencytest.c.orig	2012-11-08 17:27:56.868748156 -0500
+++ latencytest.c	2012-11-08 17:21:19.941866904 -0500
@@ -43,7 +43,8 @@
   return buf;
 }
 
-main(int argc, char ** argv) {
+
+int main(int argc, char ** argv) {
   int origpolicy;			/* Current process' scheduling
 				   priority */
   int origPolicyMaxPriority;	/* Maximum priority for the original
@@ -71,7 +72,7 @@
 	    strerror(errno));
   };
   if ((origPolicyMinPriority = sched_get_priority_min(origpolicy)) < 0) {
-    fprintf(stderr, "sched_get_priority_min(%d) failed", origpolicy,
+    fprintf(stderr, "sched_get_priority_min(%d) failed: %s", origpolicy,
 	    strerror(errno));
   };
   printf("My original scheduling policy is %s\n", PolicyToStr(origpolicy));
@@ -140,6 +141,7 @@
     /* ... */
 
     /* Return to normal priority. */
+    params.sched_priority = 0;  /* assumes orig schedule was SCHED_OTHER */
     retval = sched_setscheduler (pid, origpolicy, &params);
     if (retval < 0) {
       fprintf(stderr, "sched_setscheduler (%d, %d, ...) failed: %s\nQuiting.\n",
@@ -181,11 +183,13 @@
 	    strerror(errno));
   };
   if ((origPolicyMinPriority = sched_get_priority_min(origpolicy)) < 0) {
-    fprintf(stderr, "sched_get_priority_min(%d) failed", origpolicy,
+    fprintf(stderr, "sched_get_priority_min(%d) failed: %s", origpolicy,
 	    strerror(errno));
   };
   printf ("The minimum scheduling priority is %d, the maximum is %d\n",
 	  origPolicyMinPriority, origPolicyMaxPriority);
+
+  return EXIT_SUCCESS;
 }
 
 /**

_______________________________________________
gnhlug-discuss mailing list
gnhlug-discuss@mail.gnhlug.org
http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss/