idle_task priority and scheduling 2.1.131

Andrea Arcangeli (andrea@e-mind.com)
Thu, 3 Dec 1998 14:00:43 +0100 (CET)

The SCHED_YIELD in 2.1.131 i386/kernel/process.c should really not help.
This because the only place that care about SCHED_YIELD is goodness and
goodness() should be never run on the idle_task. The reason for using
idle_task->counter = -4 was to allow reschedule_idle() to wakeup
immediatly a sleeping process if the current one is the idle_task (and
this not achieved for sure using SCHED_YIELD).

This patch fix the idle_task priority/counter and an APM mistake:

Index: linux/arch/i386/kernel/process.c
diff -u linux/arch/i386/kernel/process.c:1.1.1.3 linux/arch/i386/kernel/process.c:1.1.1.1.2.6
--- linux/arch/i386/kernel/process.c:1.1.1.3 Thu Dec 3 12:51:05 1998
+++ linux/arch/i386/kernel/process.c Thu Dec 3 13:48:03 1998
@@ -105,19 +105,27 @@
*/
static int cpu_idle(void *unused)
{
- unsigned long start_idle = jiffies;
+ unsigned long start_time = 0;
+ int started = 0;

/* endless idle loop with no priority at all */
+ current->priority = 0;
+ /* counter must be -4 see reschedule_idle() in sched.c */
+ current->counter = -4;
for (;;) {
- if (jiffies - start_idle > HARD_IDLE_TIMEOUT)
+ if (!started)
+ {
+ start_time = jiffies;
+ started = 1;
+ }
+ if (started && jiffies - start_time > HARD_IDLE_TIMEOUT)
hard_idle();
else {
if (boot_cpu_data.hlt_works_ok && !hlt_counter && !current->need_resched)
__asm__("hlt");
}
if (current->need_resched)
- start_idle = jiffies;
- current->policy = SCHED_YIELD;
+ started = 0;
schedule();
check_pgt_cache();
}
@@ -131,12 +139,13 @@

int cpu_idle(void *unused)
{
-
/* endless idle loop with no priority at all */
+ current->priority = 0;
+ /* counter must be -4 see reschedule_idle() in sched.c */
+ current->counter = -4;
while(1) {
if (current_cpu_data.hlt_works_ok && !hlt_counter && !current->need_resched)
__asm__("hlt");
- current->policy = SCHED_YIELD;
schedule();
check_pgt_cache();
}

Andrea Arcangeli

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