On 02/24/2014 05:05 PM, Peter Zijlstra wrote:
On Mon, Feb 24, 2014 at 04:39:08PM +0100, Daniel Lezcano wrote:
And when you do that; you can also push down the
current_clr_polling_and_test() muck so it doesn't cover the actual
cpuidle policy code.
I am not getting it. Where do you suggest to move it ?
A little something like so I suppose;
Thanks for taking the time to send me this patch.
only call
current_clr_polling_and_test() right before calling the actual idle
function. Although I suppose cpuidle_enter() can still do all sorts of
weird.
Well there is the polling idle state for the x86 and ppc cpuidle
drivers. Except that, I think we have something more or less clean.
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -78,37 +78,35 @@ static int cpuidle_idle_call(void)
stop_critical_timings();
rcu_idle_enter();
- next_state = cpuidle_enabled(drv, dev);
- if (next_state < 0) {
- arch_cpu_idle();
- goto out;
- }
-
- /*
- * Ask the governor for the next state, this call can fail for
- * different reasons: cpuidle is not enabled or an idle state
- * fulfilling the constraints was not found. In this case, we
- * fall back to the default idle function
- */
- next_state = cpuidle_select(drv, dev);
+ if (cpuidle_enabled(drv, dev) == 0) {
+ /*
+ * Ask the governor for the next state, this call can fail for
+ * different reasons: cpuidle is not enabled or an idle state
+ * fulfilling the constraints was not found. In this case, we
+ * fall back to the default idle function
+ */
+ next_state = cpuidle_select(drv, dev);
+
+ if (current_clr_polling_and_test()) {
+ dev->last_residency = 0;
+ entered_state = next_state;
+ local_irq_enable();
+ } else {
+ trace_cpu_idle_rcuidle(next_state, dev->cpu);
+ entered_state = cpuidle_enter(drv, dev, next_state);
+ trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
+ }
- if (need_resched()) {
Ok. The need_resched is now replaced by 'current_clr_polling_and_test',
with a call to '__current_set_polling()' to set the flag back, right ?
For my personal information, what is the subtlety with:
if (tif_need_resched())
set_preempt_need_resched();
?
- dev->last_residency = 0;
/* give the governor an opportunity to reflect on the outcome */
- cpuidle_reflect(dev, next_state);
- local_irq_enable();
- goto out;
+ cpuidle_reflect(dev, entered_state);
+ } else {
+ if (current_clr_polling_and_test())
+ local_irq_enable();
+ else
+ arch_cpu_idle();
}
+ __current_set_polling();
- trace_cpu_idle_rcuidle(next_state, dev->cpu);
-
- entered_state = cpuidle_enter(drv, dev, next_state);
-
- trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
-
- /* give the governor an opportunity to reflect on the outcome */
- cpuidle_reflect(dev, entered_state);
-out:
if (WARN_ON_ONCE(irqs_disabled()))
local_irq_enable();
@@ -145,16 +143,11 @@ static void cpu_idle_loop(void)
* know that the IPI is going to arrive right
* away
*/
- if (cpu_idle_force_poll ||
tick_check_broadcast_expired()) {
+ if (cpu_idle_force_poll ||
tick_check_broadcast_expired())
cpu_idle_poll();
- } else {
- if (!current_clr_polling_and_test()) {
- cpuidle_idle_call();
- } else {
- local_irq_enable();
- }
- __current_set_polling();
- }
+ else
+ cpu_idle_call();
+
arch_cpu_idle_exit();
/*
* We need to test and propagate the TIF_NEED_RESCHED
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