Commit f71d2899 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds

[PATCH] Fix context switch accounting

Noted by Nick Piggin, fix based on a patch by Linus.

I've done some additional cleanups: fixed a compilation warning on UP
and cleaned up the goto pick_next_task code.  Moved the 'unlikely' to
the test as a whole.

I've tested this patch and the context-switch stats look OK.
parent 5326c535
......@@ -1470,6 +1470,7 @@ void scheduling_functions_start_here(void) { }
*/
asmlinkage void schedule(void)
{
long *switch_count;
task_t *prev, *next;
runqueue_t *rq;
prio_array_t *array;
......@@ -1516,32 +1517,25 @@ asmlinkage void schedule(void)
* if entering off of a kernel preemption go straight
* to picking the next task.
*/
if (unlikely(preempt_count() & PREEMPT_ACTIVE))
goto pick_next_task;
switch (prev->state) {
case TASK_INTERRUPTIBLE:
if (unlikely(signal_pending(prev))) {
switch_count = &prev->nivcsw;
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
switch_count = &prev->nvcsw;
if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
unlikely(signal_pending(prev))))
prev->state = TASK_RUNNING;
break;
}
default:
deactivate_task(prev, rq);
prev->nvcsw++;
break;
case TASK_RUNNING:
prev->nivcsw++;
else
deactivate_task(prev, rq);
}
pick_next_task:
if (unlikely(!rq->nr_running)) {
#ifdef CONFIG_SMP
load_balance(rq, 1, cpu_to_node_mask(smp_processor_id()));
if (rq->nr_running)
goto pick_next_task;
#endif
next = rq->idle;
rq->expired_timestamp = 0;
goto switch_tasks;
if (!rq->nr_running) {
next = rq->idle;
rq->expired_timestamp = 0;
goto switch_tasks;
}
}
array = rq->active;
......@@ -1588,6 +1582,7 @@ asmlinkage void schedule(void)
next->timestamp = now;
rq->nr_switches++;
rq->curr = next;
++*switch_count;
prepare_arch_switch(rq, next);
prev = context_switch(rq, prev, next);
......
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