From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Date: Thu, 26 Feb 2015 23:39:21 +0000 (+0100)
Subject: idle / sleep: Avoid excessive disabling and enabling interrupts
X-Git-Tag: v4.0-rc3~15^2~3^2~3
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=01e04f466e12e883907937eb04a9010533363f55;p=karo-tx-linux.git

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>
---

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;
 	}