From: Rafael J. Wysocki <[email protected]> If need_resched() returns "false", breaking out of the loop in poll_idle() will cause a new idle state to be selected, so in fact usually it doesn't make sense to spin in it longer than the target residency of the second state. [Note that the "polling" state is used only if there is at least one "real" state defined in addition to it.] On the other hand, breaking out of it early (say in case the next state is disabled) shouldn't hurt as it is polling anyway.
For this reason, make the loop in poll_idle() break if the CPU has been spinning longer than the target residency of the second state (the "polling" state can only be state[0]). Signed-off-by: Rafael J. Wysocki <[email protected]> --- drivers/cpuidle/poll_state.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: linux-pm/drivers/cpuidle/poll_state.c =================================================================== --- linux-pm.orig/drivers/cpuidle/poll_state.c +++ linux-pm/drivers/cpuidle/poll_state.c @@ -9,7 +9,6 @@ #include <linux/sched/clock.h> #include <linux/sched/idle.h> -#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16) #define POLL_IDLE_RELAX_COUNT 200 static int __cpuidle poll_idle(struct cpuidle_device *dev, @@ -21,6 +20,7 @@ static int __cpuidle poll_idle(struct cp local_irq_enable(); if (!current_set_polling_and_test()) { + u64 limit = (u64)drv->states[1].target_residency * NSEC_PER_USEC; unsigned int loop_count = 0; while (!need_resched()) { @@ -29,7 +29,7 @@ static int __cpuidle poll_idle(struct cp continue; loop_count = 0; - if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) { + if (local_clock() - time_start > limit) { dev->poll_time_limit = true; break; }
