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idle / sleep: Avoid excessive disabling and enabling interrupts

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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>
This commit is contained in:
Rafael J. Wysocki 2015-02-27 00:39:21 +01:00
parent c517d838eb
commit 01e04f466e
2 changed files with 3 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/cpuidle/cpuidle.c
View File

@ -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();
}
/**

1
kernel/sched/idle.c
View File

@ -116,7 +116,6 @@ static void cpuidle_idle_call(void)
*/
if (idle_should_freeze()) {
cpuidle_enter_freeze();
local_irq_enable();
goto exit_idle;
}