Re: [PATCH 4/4] PM / devfreq: Handle monitor start/stop in the devfreq core
From: Chanwoo Choi
Date: Thu Feb 14 2019 - 09:18:17 EST
Hi Matthias,
As I commented on the first patch, it is not possible to call some codes
according to the intention of each governor between 'devfreq_moniotr_*()'
and some codes which are executed before or after 'devfreq_moniotr_*()'
For example, if some governor requires the following sequence,
after this patch, it is not possible.
case DEVFREQ_GOV_xxx:
/* execute some code before devfreq_monitor_xxx() */
devfreq_monitor_xxx()
/* execute some code after devfreq_monitor_xxx() */
2019ë 2ì 14ì (ë) ìí 7:16, Matthias Kaehlcke <mka@xxxxxxxxxxxx>ëì ìì:
>
> devfreq expects governors to call devfreq_monitor_start/stop()
> in response to DEVFREQ_GOV_START/STOP events. Since the devfreq
> core itself generates these events and invokes the governor's event
> handler the start/stop of the load monitor can be done in the common
> code.
>
> Call devfreq_monitor_start/stop() when the governor reports a
> successful handling of DEVFREQ_GOV_START/STOP and remove these
> calls from the simpleondemand and tegra governors. Make
> devfreq_monitor_start/stop() static since these functions are now
> only used by the devfreq core. For better integration with the
> callers the functions must now be called with devfreq->lock held.
>
> Also stop manipulating the monitor workqueue directly, use
> devfreq_monitor_start/stop() instead.
>
> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> ---
> drivers/devfreq/devfreq.c | 45 +++++++++++------------
> drivers/devfreq/governor.h | 2 -
> drivers/devfreq/governor_simpleondemand.c | 8 ----
> drivers/devfreq/tegra-devfreq.c | 2 -
> 4 files changed, 22 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index eb86461648d74..ac553c00f6790 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -404,14 +404,14 @@ static void devfreq_monitor(struct work_struct *work)
> * devfreq_monitor_start() - Start load monitoring of devfreq instance
> * @devfreq: the devfreq instance.
> *
> - * Helper function for starting devfreq device load monitoing. By
> - * default delayed work based monitoring is supported. Function
> - * to be called from governor in response to DEVFREQ_GOV_START
> - * event when device is added to devfreq framework.
> + * Helper function for starting devfreq device load monitoring. By
> + * default delayed work based monitoring is supported. Must be called
> + * with devfreq->lock held.
> */
> -void devfreq_monitor_start(struct devfreq *devfreq)
> +static void devfreq_monitor_start(struct devfreq *devfreq)
> {
> - mutex_lock(&devfreq->lock);
> + WARN(!mutex_is_locked(&devfreq->lock),
> + "devfreq->lock must be held by the caller.\n");
>
> if (devfreq->profile->polling_ms) {
> INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
> @@ -420,28 +420,28 @@ void devfreq_monitor_start(struct devfreq *devfreq)
>
> devfreq->monitor_state = DEVFREQ_MONITOR_RUNNING;
> }
> -
> - mutex_unlock(&devfreq->lock);
> }
> -EXPORT_SYMBOL(devfreq_monitor_start);
>
> /**
> * devfreq_monitor_stop() - Stop load monitoring of a devfreq instance
> * @devfreq: the devfreq instance.
> *
> - * Helper function to stop devfreq device load monitoing. Function
> - * to be called from governor in response to DEVFREQ_GOV_STOP
> - * event when device is removed from devfreq framework.
> + * Helper function to stop devfreq device load monitoring. Must be
> + * called with devfreq->lock held.
> */
> -void devfreq_monitor_stop(struct devfreq *devfreq)
> +static void devfreq_monitor_stop(struct devfreq *devfreq)
> {
> + /* mutex must be held for symmetry with _start() */
> + WARN(!mutex_is_locked(&devfreq->lock),
> + "devfreq->lock must be held by the caller.\n");
> +
> + mutex_unlock(&devfreq->lock);
> cancel_delayed_work_sync(&devfreq->work);
>
> mutex_lock(&devfreq->lock);
> devfreq->monitor_state = DEVFREQ_MONITOR_STOPPED;
> mutex_unlock(&devfreq->lock);
> }
> -EXPORT_SYMBOL(devfreq_monitor_stop);
>
> /**
> * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
> @@ -518,27 +518,22 @@ void devfreq_interval_update(struct devfreq *devfreq, unsigned int *delay)
>
> /* if new delay is zero, stop polling */
> if (!new_delay) {
> + devfreq_monitor_stop(devfreq);
> mutex_unlock(&devfreq->lock);
> - cancel_delayed_work_sync(&devfreq->work);
> - devfreq->monitor_state == DEVFREQ_MONITOR_STOPPED;
> return;
> }
>
> /* if current delay is zero, start polling with new delay */
> if (!cur_delay) {
> - queue_delayed_work(devfreq_wq, &devfreq->work,
> - msecs_to_jiffies(devfreq->profile->polling_ms));
> + devfreq_monitor_start(devfreq);
> goto out;
> }
>
> /* if current delay is greater than new delay, restart polling */
> if (cur_delay > new_delay) {
> - mutex_unlock(&devfreq->lock);
> - cancel_delayed_work_sync(&devfreq->work);
> - mutex_lock(&devfreq->lock);
> + devfreq_monitor_stop(devfreq);
> if (devfreq->monitor_state != DEVFREQ_MONITOR_SUSPENDED)
> - queue_delayed_work(devfreq_wq, &devfreq->work,
> - msecs_to_jiffies(devfreq->profile->polling_ms));
> + devfreq_monitor_start(devfreq);
> }
> out:
> mutex_unlock(&devfreq->lock);
> @@ -601,6 +596,8 @@ static int devfreq_governor_start(struct devfreq *devfreq)
> return err;
> }
>
> + devfreq_monitor_start(devfreq);
> +
> return 0;
> }
>
> @@ -624,6 +621,8 @@ static int devfreq_governor_stop(struct devfreq *devfreq)
> return err;
> }
>
> + devfreq_monitor_stop(devfreq);
> +
> return 0;
> }
>
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index d136792c0cc91..47efe747b6f79 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -57,8 +57,6 @@ struct devfreq_governor {
> unsigned int event, void *data);
> };
>
> -extern void devfreq_monitor_start(struct devfreq *devfreq);
> -extern void devfreq_monitor_stop(struct devfreq *devfreq);
> extern void devfreq_interval_update(struct devfreq *devfreq,
> unsigned int *delay);
>
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index 52eb0c734b312..e0f0944a9c7aa 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -91,14 +91,6 @@ static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> unsigned int event, void *data)
> {
> switch (event) {
> - case DEVFREQ_GOV_START:
> - devfreq_monitor_start(devfreq);
> - break;
> -
> - case DEVFREQ_GOV_STOP:
> - devfreq_monitor_stop(devfreq);
> - break;
> -
> case DEVFREQ_GOV_INTERVAL:
> devfreq_interval_update(devfreq, (unsigned int *)data);
> break;
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index 79efa1e51bd06..515fb852dbad6 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -580,13 +580,11 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>
> switch (event) {
> case DEVFREQ_GOV_START:
> - devfreq_monitor_start(devfreq);
> tegra_actmon_enable_interrupts(tegra);
> break;
>
> case DEVFREQ_GOV_STOP:
> tegra_actmon_disable_interrupts(tegra);
> - devfreq_monitor_stop(devfreq);
> break;
>
> case DEVFREQ_GOV_SUSPEND:
> --
> 2.20.1.791.gb4d0f1c61a-goog
>
--
Best Regards,
Chanwoo Choi