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* [PATCH v3] PM / devfreq: passive: Use non-devm notifiers
@ 2019-08-13 11:27 Leonard Crestez
  0 siblings, 0 replies; only message in thread
From: Leonard Crestez @ 2019-08-13 11:27 UTC (permalink / raw)
  To: MyungJoo Ham, Kyungmin Park, Chanwoo Choi
  Cc: Artur Świgoń,
	Saravana Kannan, Krzysztof Kozlowski, Alexandre Bailon,
	Georgi Djakov, Lukasz Luba, Jacky Bai, Viresh Kumar, linux-pm,
	linux-arm-kernel

The devfreq passive governor registers and unregisters devfreq
transition notifiers on DEVFREQ_GOV_START/GOV_STOP using devm wrappers.

If devfreq itself is registered with devm then a warning is triggered on
rmmod from devm_devfreq_unregister_notifier. Call stack looks like this:

	devm_devfreq_unregister_notifier+0x30/0x40
	devfreq_passive_event_handler+0x4c/0x88
	devfreq_remove_device.part.8+0x6c/0x9c
	devm_devfreq_dev_release+0x18/0x20
	release_nodes+0x1b0/0x220
	devres_release_all+0x78/0x84
	device_release_driver_internal+0x100/0x1c0
	driver_detach+0x4c/0x90
	bus_remove_driver+0x7c/0xd0
	driver_unregister+0x2c/0x58
	platform_driver_unregister+0x10/0x18
	imx_devfreq_platdrv_exit+0x14/0xd40 [imx_devfreq]

This happens because devres_release_all will first remove all the nodes
into a separate todo list so the nested devres_release from
devm_devfreq_unregister_notifier won't find anything.

Fix the warning by calling the non-devm APIS for frequency notification.
Using devm wrappers is not actually useful for a governor anyway: it
relies on the devfreq core to correctly match the GOV_START/GOV_STOP
notifications.

Fixes: 996133119f57 ("PM / devfreq: Add new passive governor")
Cc: stable@vger.kernel.org
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>

---
Changes since v2:
* Add fixes: tag and reorder to be similar with other patches
* No code changes
Link to v2: https://patchwork.kernel.org/patch/11091119/

Sorry

Changes since v1:
* Remove unused variable
Link to v1: https://patchwork.kernel.org/patch/11084541/

 drivers/devfreq/governor_passive.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
index 58308948b863..be6eeab9c814 100644
--- a/drivers/devfreq/governor_passive.c
+++ b/drivers/devfreq/governor_passive.c
@@ -147,11 +147,10 @@ static int devfreq_passive_notifier_call(struct notifier_block *nb,
 }
 
 static int devfreq_passive_event_handler(struct devfreq *devfreq,
 				unsigned int event, void *data)
 {
-	struct device *dev = devfreq->dev.parent;
 	struct devfreq_passive_data *p_data
 			= (struct devfreq_passive_data *)devfreq->data;
 	struct devfreq *parent = (struct devfreq *)p_data->parent;
 	struct notifier_block *nb = &p_data->nb;
 	int ret = 0;
@@ -163,16 +162,16 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
 	case DEVFREQ_GOV_START:
 		if (!p_data->this)
 			p_data->this = devfreq;
 
 		nb->notifier_call = devfreq_passive_notifier_call;
-		ret = devm_devfreq_register_notifier(dev, parent, nb,
+		ret = devfreq_register_notifier(parent, nb,
 					DEVFREQ_TRANSITION_NOTIFIER);
 		break;
 	case DEVFREQ_GOV_STOP:
-		devm_devfreq_unregister_notifier(dev, parent, nb,
-					DEVFREQ_TRANSITION_NOTIFIER);
+		WARN_ON(devfreq_unregister_notifier(parent, nb,
+					DEVFREQ_TRANSITION_NOTIFIER));
 		break;
 	default:
 		break;
 	}
 
-- 
2.17.1


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2019-08-13 11:27 [PATCH v3] PM / devfreq: passive: Use non-devm notifiers Leonard Crestez

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