Hi Oleh,
On 2022/11/11 18:39, Oleh Kravchenko wrote:
> Hello Wang,
>
>> 11 лист. 2022 р. о 11:21 wangyufen <wangyufen@xxxxxxxxxx> написав(ла):
>>
>>
>> 在 2022/11/9 18:43, Oleh Kravchenko 写道:
>>>
>>>
>>>> 9 лист. 2022 р. о 12:25 wangyufen <wangyufen@xxxxxxxxxx> написав(ла):
>>>>
>>>>
>>>> 在 2022/11/9 17:39, Oleh Kravchenko 写道:
>>>>
>>>>>> -static void el15203000_remove(struct spi_device *spi)
>>>>>>
>>>>> Is remove() callback from struct spi_driver deprecated?
>>>>>
>>>> It is not that remove() callback is deprecated,
>>>> it's that after wrapping mutex_destroy() call with devm_add_action_or_reset(),
>>>> remove() callback is unnecessary here.
>>>>
>>> When remove() is called, the memory allocated by devm_*() is valid.
>>> So what you try to fix here?
>>
>> Fix the &priv->lock used after destroy, for details, please see patch #0
>> LKML: Wang Yufen: [PATCH 00/13] leds: Fix devm vs. non-devm ordering
>
> It doesn’t make any sense for me.
> You saying that remove() called before devm_* allocation
> if it true then set_brightness_delayed() will crash the system in anyway.
>
> LED device has a parent SPI device; LED device can’t exist without SPI device.
>
> So deallocation order should be next:
> 1. LED device devm_*()
> 2. SPI device remove()
The allocation order is as follows:
el15203000_probe()
mutex_init(&priv->lock);
el15203000_probe_dt(priv)
device_for_each_child_node(priv->dev, child) {
...
led->ldev.brightness_set_blocking = el15203000_set_blocking;
...
devm_led_classdev_register_ext(priv->dev, &led->ldev, &init_data);
dr = devres_alloc(devm_led_classdev_release, sizeof(*dr), GFP_KERNEL);
<-- dr->node.release = devm_led_classdev_release()
...
devres_add(parent, dr);
<-- add dr->node to &priv->dev->devres_head
And the full deallocation order should be this:
1. SPI device .remove callback
2. LED device devm_*()
3. SPI device deallocation
spi_unregister_device()
device_del()
bus_remove_device()
device_release_driver_internal()
__device_release_driver()
...
device_remove()
spi_remove() <-- call el15203000_remove() here, mutex_destroy(&priv->lock), lock destroy
...
device_unbind_cleanup()
devres_release_all()
release_nodes()
<-- traverse spi->dev->devres_head list and call dr->node.release in sequence.
devm_led_classdev_release()
led_classdev_unregister()
<-- flush set_brightness_work here, before the work flush, set_brightness_work may be sched.
<-- that is el15203000_set_blocking()..-> mutex_lock(&led->priv->lock) is called,
<-- this leads to the priv->lock use after destroy.
put_device(&spi->dev) <-- spi device is deallocation in here
Regards,
Wei Yongjun
