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Commit 01e04f46 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

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: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent c517d838

drivers/cpuidle/cpuidle.c

+3 −3
Original line number Diff line number Diff line
@@ -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();

}



/**

kernel/sched/idle.c

+0 −1
Original line number Diff line number Diff line
@@ -116,7 +116,6 @@ static void cpuidle_idle_call(void) 
	 */

	if (idle_should_freeze()) {

		cpuidle_enter_freeze();

		local_irq_enable();

		goto exit_idle;

	}