Re: [PATCH v2 1/6] idle: move the cpuidle entry point to the generic idle loop

Nicolas Pitre
2014-01-29T20:31:42Z

On Wed, 29 Jan 2014, Nicolas Pitre wrote:

> In order to integrate cpuidle with the scheduler, we must have a better
> proximity in the core code with what cpuidle is doing and not delegate
> such interaction to arch code.
>
> Architectures implementing arch_cpu_idle() should simply enter
> a cheap idle mode in the absence of a proper cpuidle driver.
>
> Signed-off-by: Nicolas Pitre <nico@linaro.org>
> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

As mentioned in my reply to Olof's comment on patch #5/6, here's a new
version of this patch adding the safety local_irq_enable() to the core
code.

----- >8

From: Nicolas Pitre <nicolas.pitre@linaro.org>
Subject: idle: move the cpuidle entry point to the generic idle loop

In order to integrate cpuidle with the scheduler, we must have a better
proximity in the core code with what cpuidle is doing and not delegate
such interaction to arch code.

Architectures implementing arch_cpu_idle() should simply enter
a cheap idle mode in the absence of a proper cpuidle driver.

In both cases i.e. whether it is a cpuidle driver or the default
arch_cpu_idle(), the calling convention expects IRQs to be disabled
on entry and enabled on exit. There is a warning in place already but
let's add a forced IRQ enable here as well. This will allow for
removing the forced IRQ enable some implementations do locally and
allowing for the warning to trig.

Signed-off-by: Nicolas Pitre <nico@linaro.org>

diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c
index 988573a9a3..14ca43430a 100644
--- a/kernel/cpu/idle.c
+++ b/kernel/cpu/idle.c
@@ -3,6 +3,7 @@
*/
#include <linux/sched.h>
#include <linux/cpu.h>
+#include <linux/cpuidle.h>
#include <linux/tick.h>
#include <linux/mm.h>
#include <linux/stackprotector.h>
@@ -95,8 +96,10 @@ static void cpu_idle_loop(void)
if (!current_clr_polling_and_test()) {
stop_critical_timings();
rcu_idle_enter();
- arch_cpu_idle();
- WARN_ON_ONCE(irqs_disabled());
+ if (cpuidle_idle_call())
+ arch_cpu_idle();
+ if (WARN_ON_ONCE(irqs_disabled()))
+ local_irq_enable();
rcu_idle_exit();
start_critical_timings();
} else {