Hi,
On May 10, 2015 at 01:19:52 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
>
> If tick_broadcast_enter() fails in cpuidle_enter_state(),
> try to find another idle state to enter instead of invoking
> default_idle_call() immediately and returning -EBUSY which
> should increase the chances of saving some energy in those
> cases.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
> ---
Found this during code review, hence dug up this old thread again,
> drivers/cpuidle/cpuidle.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> Index: linux-pm/drivers/cpuidle/cpuidle.c
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/cpuidle.c
> +++ linux-pm/drivers/cpuidle/cpuidle.c
> @@ -73,7 +73,10 @@ int cpuidle_play_dead(void)
> }
>
> static int find_deepest_state(struct cpuidle_driver *drv,
> - struct cpuidle_device *dev, bool freeze)
> + struct cpuidle_device *dev,
> + unsigned int max_latency,
> + unsigned int forbidden_flags,
> + bool freeze)
> {
> unsigned int latency_req = 0;
> int i, ret = freeze ? -1 : CPUIDLE_DRIVER_STATE_START - 1;
> @@ -83,6 +86,8 @@ static int find_deepest_state(struct cpu
> struct cpuidle_state_usage *su = &dev->states_usage[i];
>
> if (s->disabled || su->disable || s->exit_latency <= latency_req
> + || s->exit_latency > max_latency
> + || (s->flags & forbidden_flags)
> || (freeze && !s->enter_freeze))
> continue;
>
> @@ -100,7 +105,7 @@ static int find_deepest_state(struct cpu
> int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
> struct cpuidle_device *dev)
> {
> - return find_deepest_state(drv, dev, false);
> + return find_deepest_state(drv, dev, UINT_MAX, 0, false);
> }
>
> static void enter_freeze_proper(struct cpuidle_driver *drv,
> @@ -139,7 +144,7 @@ int cpuidle_enter_freeze(struct cpuidle_
> * that interrupts won't be enabled when it exits and allows the tick to
> * be frozen safely.
> */
> - index = find_deepest_state(drv, dev, true);
> + index = find_deepest_state(drv, dev, UINT_MAX, 0, true);
> if (index >= 0)
> enter_freeze_proper(drv, dev, index);
>
> @@ -168,8 +173,13 @@ int cpuidle_enter_state(struct cpuidle_d
> * CPU as a broadcast timer, this call may fail if it is not available.
> */
> if (broadcast && tick_broadcast_enter()) {
> - default_idle_call();
> - return -EBUSY;
> + index = find_deepest_state(drv, dev, target_state->exit_latency,
> + CPUIDLE_FLAG_TIMER_STOP, false);
> + if (index < 0) {
Would this condition ever meet?
If you see, the ret inside find_deepest_state is always starting with a 0 and
then nobody is ever really making it negative again. So the func either
returns a 0 or some positive value right?
Since nobody has probably raised an issue about this in 9 years, is this
basically dead code inside the if?
Let me know what needs to be done here, I'd be happy to patch this up.
> + default_idle_call();
> + return -EBUSY;
> + }
> + target_state = &drv->states[index];
> }
>
> /* Take note of the planned idle state. */
>
--
Best regards,
Dhruva Gole <d-g...@ti.com>
