From e7387da52028b072489c45efeb7a916c0205ebd2 Mon Sep 17 00:00:00 2001 From: Daniel Lezcano Date: Tue, 17 May 2016 16:54:00 +0200 Subject: [PATCH] cpuidle: Fix cpuidle_state_is_coupled() argument in cpuidle_enter() Commit 0b89e9aa2856 (cpuidle: delay enabling interrupts until all coupled CPUs leave idle) rightfully fixed a regression by letting the coupled idle state framework to handle local interrupt enabling when the CPU is exiting an idle state. The current code checks if the idle state is coupled and, if so, it will let the coupled code to enable interrupts. This way, it can decrement the ready-count before handling the interrupt. This mechanism prevents the other CPUs from waiting for a CPU which is handling interrupts. But the check is done against the state index returned by the back end driver's ->enter functions which could be different from the initial index passed as parameter to the cpuidle_enter_state() function. entered_state = target_state->enter(dev, drv, index); [ ... ] if (!cpuidle_state_is_coupled(drv, entered_state)) local_irq_enable(); [ ... ] If the 'index' is referring to a coupled idle state but the 'entered_state' is *not* coupled, then the interrupts are enabled again. All CPUs blocked on the sync barrier may busy loop longer if the CPU has interrupts to handle before decrementing the ready-count. That's consuming more energy than saving. Fixes: 0b89e9aa2856 (cpuidle: delay enabling interrupts until all coupled CPUs leave idle) Signed-off-by: Daniel Lezcano Cc: 3.15+ # 3.15+ [ rjw: Subject & changelog ] Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/cpuidle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 2b8e6ce62e81..a4d0059e232c 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -214,7 +214,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, tick_broadcast_exit(); } - if (!cpuidle_state_is_coupled(drv, entered_state)) + if (!cpuidle_state_is_coupled(drv, index)) local_irq_enable(); /* -- 2.39.5