> hmm, maybe my mail wasn't clear enough. I'll try to explain the real aim again:
>
> I'd like to have a processes doing real and reasonable computations
> only and really only if nothing else is running on the system.
> it should not even try to compete with jobs running with "nice 19".
> this is what I'm calling my "idle task".
>
> the "while (1);" loop was only a short replacement for the real computation...
maybe we could (ab)-use the RT system calls to set 'idle' priority for
processes. (priority which is unsettable with the normal Posix system
calls)
[some time passes]
what about this patch. Idle priority seems to fit into setscheduler()
nicely.
[i hope it doesnt break Posix?]
--- sched.h.orig Sun Apr 13 19:11:15 1997
+++ sched.h Sun Apr 13 19:11:41 1997
@@ -93,6 +93,7 @@
#define SCHED_OTHER 0
#define SCHED_FIFO 1
#define SCHED_RR 2
+#define SCHED_IDLE 3
struct sched_param {
int sched_priority;
@@ -212,7 +213,8 @@
struct wait_queue *wait_chldexit; /* for wait4() */
unsigned short uid,euid,suid,fsuid;
unsigned short gid,egid,sgid,fsgid;
- unsigned long timeout, policy, rt_priority;
+ unsigned long timeout, policy;
+ long rt_priority;
unsigned long it_real_value, it_prof_value, it_virt_value;
unsigned long it_real_incr, it_prof_incr, it_virt_incr;
struct timer_list real_timer;
--- sched.c.orig Sun Apr 13 19:04:17 1997
+++ sched.c Sun Apr 13 19:09:22 1997
@@ -1485,7 +1485,7 @@
if (policy < 0)
policy = p->policy;
else if (policy != SCHED_FIFO && policy != SCHED_RR &&
- policy != SCHED_OTHER)
+ policy != SCHED_OTHER && policy != SCHED_IDLE)
return -EINVAL;
/*
@@ -1504,7 +1504,15 @@
return -EPERM;
p->policy = policy;
- p->rt_priority = lp.sched_priority;
+
+ if (policy == SCHED_IDLE)
+ /*
+ * look into goodness() before complaining ;)
+ */
+ p->rt_priority = -1999;
+ else
+ p->rt_priority = lp.sched_priority;
+
spin_lock(&scheduler_lock);
spin_lock_irq(&runqueue_lock);
if (p->next_run)