From 01e04f466e12e883907937eb04a9010533363f55 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Fri, 27 Feb 2015 00:39:21 +0100
Subject: [PATCH] idle / sleep: Avoid excessive disabling and enabling
interrupts
Disabling interrupts at the end of cpuidle_enter_freeze() is not
useful, because its caller, cpuidle_idle_call(), re-enables them
right away after invoking it.
To avoid that unnecessary back and forth dance with interrupts,
make cpuidle_enter_freeze() enable interrupts after calling
enter_freeze_proper() and drop the local_irq_disable() at its
end, so that all of the code paths in it end up with interrupts
enabled. Then, cpuidle_idle_call() will not need to re-enable
interrupts after calling cpuidle_enter_freeze() any more, because
the latter will return with interrupts enabled, in analogy with
cpuidle_enter().
Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
drivers/cpuidle/cpuidle.c | 6 +++---
kernel/sched/idle.c | 1 -
2 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 4d534582514e..b573f584b15a 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -117,6 +117,8 @@ static void enter_freeze_proper(struct cpuidle_driver *drv,
* If there are states with the ->enter_freeze callback, find the deepest of
* them and enter it with frozen tick. Otherwise, find the deepest state
* available and enter it normally.
+ *
+ * Returns with enabled interrupts.
*/
void cpuidle_enter_freeze(void)
{
@@ -132,6 +134,7 @@ void cpuidle_enter_freeze(void)
index = cpuidle_find_deepest_state(drv, dev, true);
if (index >= 0) {
enter_freeze_proper(drv, dev, index);
+ local_irq_enable();
return;
}
@@ -144,9 +147,6 @@ void cpuidle_enter_freeze(void)
cpuidle_enter(drv, dev, index);
else
arch_cpu_idle();
-
- /* Interrupts are enabled again here. */
- local_irq_disable();
}
/**
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 94b2d7b88a27..f59198bda1bf 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -116,7 +116,6 @@ static void cpuidle_idle_call(void)
*/
if (idle_should_freeze()) {
cpuidle_enter_freeze();
- local_irq_enable();
goto exit_idle;
}